A COMMENTARY on ARC TP 58, 3rd Edition 2004 - WordPress.com · 12/2/2013 · Section 2.1.3 [p. 8] states that: TP 58 is not a statutory document in itself, under the Resource Management

TP58 3rd

Edition Commentary – Ian Gunn, 16 December 2004

1

TECHNICAL COMMENTARY on ARC TP58, 3rd

Edition 2004 – ON-SITE WASTEWATER SYSTEMS: DESIGN AND MANAGEMENT MANUAL

PART 1: CHAPTERS 1 TO 13

Prepared By: Ian Gunn

Editor, On-Site NewZ

Date: 16 December 2004

Item Section/Page No Content Commented Upon Commentary and Recommendations

1 Section 1.3 [p. 2] New joint Australian and New Zealand Standards have now also been issued in parallel to the drafting of these revised guidelines. These are as follows:

AS/NZS 1546.1:1998 On-site domestic wastewater treatment units Part 1: Septic tanks

AS/NZS 1546.3:2001 On-site domestic wastewater treatment units Part 3: Aerated wastewater treatment systems

AS/NZS 1547:2000 On-site domestic wastewater management

Further joint Standards in the AS/NZS 1546 series are being issued for “waterless composting toilets” and other systems.

This statement is incomplete, as the composting toilet standard was issued in 2001,

and no other treatment unit standards are currently in preparation, or about to be

issued.

Recommendation: Replace text with: New joint Australian and New Zealand Standards have now also been issued in parallel to the drafting of these revised guidelines. These are as follows:

AS/NZS 1546.1:1998 On-site domestic wastewater treatment units Part 1: Septic tanks

AS/NZS 1546.2:2001 On-site domestic wastewater treatment units Part 2: Waterless composting toilets

AS/NZS 1546.3:2001 On-site domestic wastewater treatment units Part 3: Aerated wastewater treatment systems

AS/NZS 1547:2000 On-site domestic wastewater management

2 Section 1.3 [p. 2] Appendix B includes technical reasons concerning on why TP58 is considered more appropriate and relevant to the Auckland region than the AS/NZS standards.

The Part 2: Appendices Commentary notes in respect of Appendix B that some of

the reasons given for the preference of TP58 over AS/NZS 1547 have been based

upon a misinterpretation of some of the provisions of the Standard.

3 Section 1.3 [p. 2] Where information is lacking in these guidelines, reference should be made to the relevant literature, where further information is required, consideration should be given to the relevant design criteria as specified in the AS/NZS standards [Ref 1] and/or USEPA Manual [Ref 5] and/or Crites & Tchobanoglous, “Small and Decentralised Wastewater Management Systems” (1998) [Ref 2].

The reference number for the USEPA Manual is [Ref 3], not [Ref 5].

Recommendation: Edit accordingly here on p. 2, and also on p. 38.

4 Section 1.3 [p. 2 and

3]

This edition is issued with the acknowledgement that scope remains for further technical details and expansion of some chapters. To address anticipated gaps and changes in the wastewater industry over time and corresponding needs for more detailed guidelines, TP 58 will require revision again in the forthcoming years and/or new addenda and/or technical sheets will be produced where gaps are identified. In the interim, where a design detail is outside the recommended specifications in TP58 the appropriate mechanism for approval is via the resource consent process. Once the particular new design specifications have been proven to meet the objectives of TP58 for effective and sustainable on-site treatment and disposal to the reasonable satisfaction of the ARC, then the intent is that bit will be incorporated into TP58 via an addendum as appropriate, following a notified variation to the proposed Regional Plan: Air, Land and Water.

Section 2.1.3 [p. 8] states that: TP 58 is not a statutory document in itself, under the Resource Management Act 1991, but it is a technical guideline manual, developed by ARC to provide suitable design standards for on-site wastewater treatment and land application systems in the Auckland region.

And the Preface [p. i] states: This edition of TP58 is issued with the acknowledgement that scope remains for further technical details and expansion of detail in some chapters. To address anticipated needs for more detailed guidelines over time, TP58 will require revision again in due course and/or new addenda and/or technical sheets will be produced where gaps are identified.

Hence, it is clear the ARC intends to keep TP58 current, although it is not clear if

the process of “notified variation’” will enable speedy revisions and additions

particularly where clear discrepancies are found within the technical provisions in

this edition as issued August 2004.

Recommendation: The ARC develop a mechanism for issuing “advisory notes” or

equivalent so as to update, add to and/or correct TP58 provisions in advance of

formal processes associated with confirming changes to the manual.

TP58 3rd


2


5 Section 2.6.2 [p.14] For the proposed new PA rules ----- the First PA Rule (Rule 5.5 20) This rule also requires secondary treatment and disposal by drip irrigation in accordance with TP58, along with other design criteria.

The amendments to Chapter 5 of the Proposed Regional Plan: Air, Land and Water

(PARP:ALW) as notified by Decision Notice 25 of October 2004 have revised Rule

numbering. The provisions of Rule 5.5.20 are now covered by 5.5 22. In 5.5.22 it is

not totally clear that secondary treatment and drip irrigation must be used, but this

2.6.2 statement confirms this is the case.

Recommendation: Edit Rule numbering to fit current version of ARP:ALW.

6 Section 4.3 [p. 24]

and Table 4.1 [p. 25]

A Decentralised Wastewater Management System (DWTS) refers to a single combined treatment system serving a group or cluster of sites, compared to the centralised systems, which refer to the reticulation and treatment system serving all properties within a whole town or city.

The use of the abbreviation DWTS would relate to Decentralised Wastewater

Treatment System. This terminology is also used in Table 4.1 for decentralised,

centralised and on-site systems (DWTS; CWTS; OWTS). However, to be consistent

with the theme of and definitions in Section 3 “On-site Wastewater Management”,

and with headings and text of Sections 4.2.2 and 4.3 it seems appropriate to stick

with “management” instead of “treatment” in reference to decentralised, centralised

and on-site systems. [See also Items 274, 275 and 283 below.]

Recommendation: Change DWTS, CWTS and OWTS to DWMS, CWMS and

OWMS, and replace “treatment” with “management” in all relevant locations.

7 Section 4.4.1 [p. 29] Reuse of wastewater is discussed further in Section 7.8 Section 7.7 (not 7.8) discusses use of treated wastewater effluent.

Recommendation: Edit Section number, and amend wording to avoid term “reuse

of wastewater” – wastewater is not reused, but can be treated to reclaim water for

reuse/recycle). Change text to: Use of treated wastewater effluent for reuse/recycle is discussed further in Section 7.7.

8 Section 4.4.5 [p.32] The requirement for a discharge consent is assessed on a case by case basis, against ARC rules for on-site wastewater systems (discussed further in Section 2.5 and in Appendix c).

The correct reference is Section 2.6, not 2.5.

Recommendation: Edit accordingly.

9 Section 5.1 [p.34] Select the appropriate land disposal system (Figure 5.1) Figure 5.1 [p. 35] is the incorrect reference. Figure 5.2 [p.42] is the appropriate

Figure.

Recommendation: Change all three references to Figure 5.1 on page 34 to 5.2, as

well as that on page 41.

10 Section 5.1 [p.34] In this manual, the range of recommended design land application rates for each type of land disposal system and Soil Category is detailed in Figure 5.1, Table 10.3 and in Chapters 9 & 10.

This statement needs amending to provide clearer guidance as to selection of

system, and then the assignment of design land application rates. The references to

Figure 5.1 and Table 10.3 are also incorrect.

Recommendation: Replace text with: In this manual, the range of land application systems appropriate for each Soil Category is detailed in Figure 5.2 and Table 10.4, with design land application rates for each type of land disposal system and Soil Category set out in the tables of recommended loading rates in Chapters 9 & 10.

11 Section 5.2.2 [p.38] SOILS – The USEPA On-site Wastewater Treatment Systems Manual 2002 Sections 4.4.5 and 5.5.7 [Ref 5] and in AS/NZS 1547:2000 Section 4.1D, all provide soil description procedures [Ref 1].

The referred sections of the USEPA manual do not fit (and the Ref No. is 3, not 5).

Recommendation: Replace text with: The USEPA On-site Wastewater Treatment Systems Manual 2002 Section 5.5.6 [Ref 3] and AS/NZS 1547:2000 Section 4.1D [Ref 1], both provide soil description procedures.

TP58 3rd


3


12 Section 5.3.3 [p. 39

and 40] 5.3.3 Soil Permeability Testing Traditional percolation testing, as per the withdrawn NZS 4610:1982 and previous editions of TP 58 (refer “Table 5.2: Soil texture and Percolation Rates – USEPA Design Manual 10980”,in the Second Edition of TP58), is not provided for in this edition as a test method for assisting in determining soil infiltration capacity. Any percolation test results may only being used to support or check an individual designer’s conclusions regarding Soil Category, and must not be used (as has been done in the past) as the sole criteria on which decisions on site suitability and design of land application system are made. Soil percolation testing has been superseded by the Soil Type method (soil categorization) detailed below in Section 5.4. Design loading rates must be selected according to soil type and site constraints. Percolation testing thus has a limited role in the design process covered in this manual.

Note: Soil permeability testing is a useful tool to help confirm the Soil Category for design purposes, particularly if there is any element of doubt, or if the design is not to be conservative, but permeability test results are not used as the sole determinant of soil category. The designer must be aware that soil permeability testing results can be highly misleading and can indicate high soakage capacity in category 5 or 6 soils for example through short circuiting via shrinkage cracks. Many designers have in the past too readily accepted permeability test results in preference to categorisation of the soil types following investigation of actual soil properties, which has resulted in a land application systems being designed to fail.

The heading of this section refers to soil permeability testing, but then only

discusses soil percolation testing in the substantive text. Only the Note addresses

“permeability testing”, but even then there appears to be confusion between the

terms “percolation” and “permeability”. Any suggestion that falling head

percolation testing has any role in on-site system site and soil assessment should be

put to rest forthwith. However, the constant head permeability (clean water

hydraulic conductivity as Ksat) test procedures of AS/NZS 1547:2000 can usefully

be incorporated into TP58.

Recommendation: Replace text with:

5.3.3 Soil Permeability Testing Traditional falling head percolation testing, as per the withdrawn NZS 4610:1982 and previous editions of TP 58 (refer “Table 5.2: Soil texture and Percolation Rates – USEPA Design Manual 1980”, in the Second Edition of TP58), is not provided for in this edition as a test method for assisting in determining soil infiltration capacity. Falling head percolation test results must not be used (as has been done in the past) as criteria on which decisions on site suitability and design of land application system are made. Soil Category determination using falling head soil percolation test results has been superseded by the Soil Type method (soil categorization) detailed below in Section 5.4. Design loading rates must be selected according to soil type and site constraints.

Note 1: Percolation testing thus has no role in the design process covered in this manual. The designer must be aware that percolation test results can be highly misleading and can indicate high soakage capacity in category 5 or 6 soils for example through short circuiting via shrinkage cracks. Many designers have in the past too readily accepted falling head percolation test results in preference to categorisation of the soil types following investigation of actual soil properties, which has resulted in a land application systems being designed to fail.

Constant head permeability testing (to determine soil hydraulic conductivity in terms of Ksat) may be used to support or check an individual designer’s conclusions regarding Soil Category, but must not be used as the sole criteria on which decisions on site suitability and design of land application system are made.

Note 2: Constant head soil permeability testing is a useful tool to help confirm the Soil Category for design purposes, particularly if there is any element of doubt, or if the design is not to be conservative (refer AS/NZS 1547:2000, Sections 4.1.1, 4.1A7, 4.2A5.3, Table 4.1.1, Notes 2 and 3, and Table 4.2A1, Note 11).

TP58 3rd


4


13 Section 5.4.1 [p.40] 5.4.1 Soil Category Descriptions Soil Category classes have been based on soil texture (grain size) along with an indication of clean water percolation capacity for each texture class. The assignment of Soil Categories for design purposes based on site and soil information becomes a somewhat subjective process where the investigator/designer has to bring judgement into the determination. However, by using soil morphology information supported as appropriate by soil textural analysis and possibly permeability testing, there are ample tools available to the investigator/designer to enable an appropriate determination of Soil Category.

The terms “percolation” and “permeability” have again been used inappropriately.


5.4.1 Soil Category Descriptions Soil Category classes have been based on soil texture (grain size) along with an indication of clean water natural drainage capacity for each texture class. The assignment of Soil Categories for design purposes based on site and soil information becomes a somewhat subjective process where the investigator/designer has to bring judgement into the determination. However, by using soil morphology information supported as appropriate by soil textural analysis and possibly constant head permeability testing (hydraulic conductivity, Ksat), there are ample tools available to the investigator/designer to enable an appropriate determination of Soil Category.

14 Section 5.4.1 [p.40] Within AS/NZS 1547:2000, design loading rate (DLR) values within each soil category are subdivided according to structural classification. Similarly, in this edition of TP 58, it is intended that designers make allowance for soil structural influence on soil infiltration capacity by adjusting the Soil Category selected for design purposes in an appropriate manner, or interpolating loading rate values between Soil Categories (refer Section 5.4.2 below).

The use of the term “similarly” in reference to the structural classifications in

AS/NZS 1547:2000 is inappropriate.

Recommendation: Replace text with: Within AS/NZS 1547:2000, design loading rate (DLR) values within each soil category are subdivided according to structural classification. Although similar structural classifications are not set out in the tables relating to soil category in this edition of TP 58, it is intended that designers make allowance for soil structural influence on soil infiltration capacity by adjusting the Soil Category selected for design purposes in an appropriate manner, or interpolating loading rate values between Soil Categories (refer Section 5.4.2 below).

15 Section 5.4.2 [p.41] d. Complete item 5.3 of the Appendix E checklist (this provides the estimated Soil Category from the site information).

This item has been left in from the July 2003 draft.

Recommendation: Replace text with: d. Complete Part D, Item 7 of the Appendix E checklist (this provides the estimated Soil

Category from the site information).

16 Figure 5.2 [p. 42]

[see also Items 9

and 10 above]

Figure 5.2: On-site Land Disposal Systems According to

Soil Category

This Figure is an update of the original Fig. 5.1 of the second edition of TP58. It is

repeated in reconfigured form as Table 10.4 on page 168, although there are some

discrepancies in Table 10.4 (which also is incomplete, since it refers to

recommended loading rates – these are missing from the table). Table 10.4 has been

recommended to be substantially revised (and relocated) [see Items 199, 200 and

253 below].

The real issue with this Table 5.2 (which has been mis referred to as Table 5.1 in

several places in the text) is the allocation of discharge control trench across drip

irrigation. Table 9.1 dealing with drip irrigation systems requires discharge control

trenches to be provided under drip line distribution for Category 1 and 2 soils, and

commentary on this measure is provided under Item 137 below. This recommends

that drip irrigation for Category 1 and 2 soils be undertaken with design layout using

300mm by 300mm dripline and emitter spacings.

Recommendation: Revise Figure 5.2 in the light of changes to Table 10.4 as per Item 200 and page 43

below.

TP58 3rd


5


17 Section 5.5 [p.41]

and Table 5.2 [p.43]

The minimum distances are also dependant upon potential for adverse effects, specifically impacts on surface or ground water quality , and therefore vary depending on the type of treatment and therefore final treated wastewater quality.

The text herein and the content of the table relate only to effluent quality variation,

and do not allow for variation in land application method. For example, mounds are

specially designed to achieve satisfactory secondary treatment over shallow water

tables 300mm to 600mm below base of the mound (as laid on ground surface). In

addition, disinfection can enable drip irrigation into subsoils where only 300mm

clearance to groundwater is available.

Recommendations: (a) Replace text with: The minimum distances are also dependant upon potential for adverse effects, specifically impacts on surface or ground water quality, and therefore vary depending on the type of treatment, the resulting treated wastewater quality, and the type of land application disposal system used. Minimum separation distances may be relaxed where special design precautions are taken, subject to approval by the consent authorities.

(b) In the space between the Table and the Notes on page 43, amend the highlighted

comment as follows: [All separation distances may vary dependant upon territorial authority requirements. They may also be reduced on a case by case basis as part of a discharge consent application]

18 Table 5.2 [p.44] Notes: 6. Groundwater or groundwater cutoff trench clearance distance is defined as the vertical distance from the base of the land application system to the highest seasonal water table level.

What is meant by “groundwater cutoff trench clearance distance”? This does not seem to

make sense.

Recommendation: Replace text with: 6. Groundwater clearance distance is defined as the vertical distance from the base of the land application system to the highest seasonal water table level.

19 Table 5.2 [p.44] Notes: 7. Groundwater separation distances and limitations on discharges within certain floodplains may be reduced on a case by case basis as part of a discharge consent application.

Given the changes recommended under Item 17 above, this note can be amended.

Recommendation: Replace text with: 7. Groundwater separation distances and limitations on discharges within certain floodplains may be reduced through use of appropriate land application disposal systems and design procedures. Their adoption should be on a case by case basis as part of a discharge consent application.

20 Table 5.2 [p.44] Notes: 10. The nutrient type ---- risk level. The maximum total nitrogen level is 10mg/l.

Notes 12 and 13 are a repeat of Notes 9 and 10. In Note 10 the reference to nitrogen

level is incomplete, and needs clarification (see Item 257 below).

Recommendations: (a) Delete Notes 12 and 13.

(b) Amend Note 10 as follows: 10. The nutrient type ---- risk level. For example, the drinking water standard for nitrogen is 10g/m

3 NO3-N.

TP58 3rd


6


21 Table 5.3 [p.46] * An additional 40-50% reserve allocation should be added where the design flow is based on greywater only with all toilet wastewater discharged to a compost toilet. Further discussion of this requirement and composting systems is provided in section 7.8.2.

This single asterisk deals with special provisions for greywater management, and

thus should really only be assigned to the five primary effluent systems, all of which

are set at 100% (excludes the four drip and secondary effluent trench/bed systems).

Recommendation: (a) Place asterisk against all five primary effluent systems, and delete it from

column heading.

(b) Replace text with [and note that 7.8.2.8. becomes 7.8.2.9 (see Item 111 below)]. * The reserve allocation should be 140% to 150% where the design flow is based on greywater only with all toilet wastewater discharged to a compost toilet. Further discussion of this requirement and composting systems is provided in section 7.8.2.9. If the greywater system is sized for full wastewater flows in accordance with Section 7.8.1.2, then a 100% reserve area allocation will be satisfactory.

22 Table 5.3 [p.46]

ETS Beds**, Aerobic Soakage Beds and Trenches

Secondary Effluent to Trenches or Beds (with double loading rate***)

** ETS means Evapotranspiration Seepage Beds which are covered further in Section 10.3 *** At time of printing, double loading rates for secondary treated wastewater were not approved within the Auckland Region.

Why are ETS Beds asterisked with a referral to Section 10.3? This seems

unnecessary. In addition, Aerobic Soakage Beds (ASB) are spelt out in full.

However, I cannot find any reference to design details for ASB systems in the

manual (see Item 210 below). Furthermore, the reference to “time of printing” is

inappropriate.

Recommendations: Amend and replace text as follows:

ETS (evapo-transpiration seepage) Beds and Trenches

Secondary Effluent to Trenches or Beds (with double loading rate**)

** ETS means Evapotranspiration Seepage Beds which are covered further in Section 10.3 ** Double loading rates for secondary treated wastewater are not a” permitted activity” within the Auckland Region.

23 Table 5.3 [p.46] Notes: 2. Reserve area can be reduced where secondary effluent is proposed.

This is automatically built into the table for the four secondary effluent land

application systems. It is presumed this note applies to the five primary effluent

systems. Note also that the 100% reserve area for shallow trenches can be waived if

trench spacing is 2.0m or more (see Item 165 below)

Recommendations: (a) Replace text with the following: 2. Reserve area can be reduced where secondary effluent is discharged to those systems normally designed for primary effluent.

(b) Add a new Note 3, and renumber subsequent notes: 3. For shallow trench systems, where the minimum space between individual trenches is 2.0m or more, then the reserve area becomes the space between trenches (Section 10.1.3).

TP58 3rd


7


24 Table 5.3 [p.46] Notes: 3. In all cases 100% reserve area is required with primary effluent, except in areas with out a permanent power supply where 40 to 50% reserve area is permitted in the Auckland region due to the more conservative approach to wastewater management.

This statement is quite confusing as it is making reference to provisions in the

PARP:ALW which relate to a specific permitted activity rule, and should be

discussed elsewhere outside of TP58, and not raised in a Note to this Table.

Recommendation: Amend text to: 4. In all cases 100% reserve area is required with primary effluent.

25 Table 5.3 [p.46] as

well as Figure 5.2

[p.42] and Table

10.4 [p.168]

Land Disposal Systems/Methods as set out in the three

Figures/Tables.

There is a lack of consistency in the terminology and coverage of systems/methods

in these three items. For example LPP/LPED systems are omitted from Table 5.3 [p.

46].

Recommendation: Review each Figure/Table and ensure consistency of

terminology across all. [See Item 16 above, and Items 199, 200 and 253 below.]

26 Table 6.1 [p. 51] Notes: 3. Design occupancy should allow for a seasonal peak, not just the average daily flow. Holiday homes tend to have intermittent occupancy but when occupied are likely to have a higher occupancy than a continuously occupied dwelling. An allowance in design occupancy should be made for the seasonally higher flows.

Guidance should be given in how to allow for this seasonal peak in case designers

presume that land applications systems are to be sized on peak flows when in fact

average flows and conservative DLR values will in fact suffice.

Recommendation: Replace text with: 3. Design occupancy should allow for a seasonal peak, not just the average daily flow. Holiday homes tend to have intermittent occupancy but when occupied are likely to have a higher occupancy than a continuously occupied dwelling. An allowance for the seasonally higher flows due to peak occupancy can be made by providing for peak flow storage within the treatment and/or land application system, and/or the use of a conservative design loading rate in sizing the land application system.

27 Table 6.2 [p.54] Notes: 13. Flow rates ----- there is no bath. Applicable where solids from kitchen and toilet waste flows are excluded from the wastewater stream. For households with low ------.

Greywater by definition excludes toilet waste but includes kitchen sink flows. So

what is the relevance of this statement? Is the absence of a garbage grinder being

targeted here? If so, say so.

Recommendation: Replace text with: 13. Flow rates ----- there is no bath. Applicable where solids from kitchen flows are excluded from the wastewater stream (no garbage grinder). For households with low ------.

28 Table 6.2 [p.55] Notes: 16. Assumes that lunches and lunch/dinners will be served, and that overnight visitors have access to showers but not laundry facilities. Water meter readings should be installed to provide added certainty to the accuracy in the design flow allowance. The designer should be aware that water conservation measures installed in commercial premises eg; bars, restaurants may not provide the same level of savings as achieved by domestic uses. Unless specified metered consumption information is available conservative flow allowances should be applied.

The first two sentences apply suitably to the Marae category, but the next two

sentences relate to general commercial activities.

Recommendations: (a) Replace text with: 16. Assumes that lunches and lunch/dinners will be served, and that overnight visitors have access to showers but not laundry facilities. Water meters should be installed and readings taken to provide added certainty to the accuracy in the design flow allowance.

(b) Introduce a new Note 23, and assign it to the sub-title for the “commercial flow

allowances” as follows:

Commercial Flow Allowances for Standard Fixtures [Note 23]

23. The designer should be aware that water conservation measures installed in commercial premises e.g. bars, restaurants may not provide the same level of savings as achieved by domestic uses. Unless specific metered consumption information is available conservative flow allowances should be applied.

TP58 3rd


8


29 Section 6.3.5 [p. 59] f. The maximum daily flow discharge volume to the land application system is checked to ensure that sufficient storage capacity for that flow is available within the treatment system; and g. If sufficient peak flow storage is not available in the designed treatment system, the capacity of a separate or supplementary storage system is determined.

Since the land application system can accept overload via flood storage of treated

effluent which then is absorbed and infiltrated during the rest period between uses,

storage within both the treatment unit and the land application area is appropriate.

Recommendation: Replace text with: f. The maximum daily flow discharge volume to the land application system is checked to ensure that sufficient storage capacity for that flow is available within the treatment and/or land application system; and

g. If sufficient peak flow storage is not available in the designed treatment and/or land application system, the capacity of a separate or supplementary storage system is determined.

30 Section 7.1 [p.62] The term "treatment" refers to all technologies used to retain and treat wastewater residuals prior to discharge of the treated effluent to a land application system (such as pressure compensating dripper irrigation, seepage trenches, or evapo-transpiration beds). All components of an on-site system thus provide “treatment”, to a varying degree. The treatment stages can be engineered to achieve specific design objectives in terms of minimising public health and environmental risks. The various treatment technologies provide a range of treatment levels. Design specifications are provided in this chapter for the following core treatment systems. These are listed by the stage of treatment that they provide in increasing order of degree of treatment:

The way these two paragraphs are written and structured does not convey the intent

of the first sentence of the second paragraph (All components of an on-site system thus

provide “treatment”, to a varying degree), which is to indicate that “treatment” is a

component of both the treatment unit and the land application system. Note also that

the text on page 62 of this introduction uses “treatment unit” and “treatment system”

interchangeably.

Recommendation: Replace text with: The term "treatment" refers to all technologies used to retain and treat wastewater residuals via a treatment unit prior to discharge of the treated effluent to a land application system. The land application system (such as pressure compensating dripper irrigation, seepage trenches, or evapo-transpiration beds) provides further “treatment” of the treated effluent discharge due to natural processes within the soil. All components of an on-site wastewater management system thus provide “treatment” to a varying degree. The treatment unit stages can be engineered to achieve specific design objectives in terms of producing effluent quality aimed at minimising public health and environmental risks. The various treatment unit technologies provide a range of treatment levels. Design specifications are provided in this chapter for the following core treatment unit systems. These are listed by the stage of treatment that they provide in increasing order of degree of treatment.

TP58 3rd


9


31 Section 7.1 [p.62] Secondary Treatment:

Aerobic treatment plants [AWTS] (aerated wastewater treatment

systems; biofilter treatment units)

TP58 has adopted particular terminologies for aerobic treatment units based around

the AS/NZS approach. I have always disagreed with the blanket use of AWTS

(aerated wastewater treatment system) to be inclusive of aerobic biofilter units and

rotating biological contactors and argued at the Joint Standards Committee that

AWTS apply only to extended aeration activated sludge systems. However, the

Australians were so familiar with AWTS being only (to them) the activated sludge

system that they prevailed. I was only able to get them to include reference to the

other aerobic treatment units via a mention in the Preface.

So, TP58 needs to be consistent. Designating “aerobic treatment plants” (or ATP) as

“AWTS” clearly is not consistent, and although my preference would be to use

ATP, I will base further commentary on accepting the terminology in TP58.


Secondary Treatment: Aerated wastewater treatment systems [AWTS] (activated sludge treatment units; biofilter treatment units)

32 Table 7.1 [p. 63] BOD2 Recommendation: Edit to: BOD5

33 Table 7.1 [p. 63] Septic Tank (poor operation) BOD5 7 to 250 Recommendation: Edit to: Septic Tank (poor operation) BOD5 70 to 250

34 Table 7.1 [p. 63] S T plus Intermittent Sand Filter FC 4x102 to 10

4 The upper limit of 10,000 is inconsistent with the 2

nd Edition value of 1,000, and

contradictory to Note 9. Change accordingly (unless superior knowledge from the

range of references cited is available).

Recommendation: Edit to: S T plus Intermittent Sand Filter FC 4x10

2 to 10

3

35 Table 7.1 [p. 64] Notes: 5. AS-AWTS refers to activated sludge aerobic wastewater treatment plant

In terms of the requirement for consistency as discussed in Item 31 above, this

needs changing.

Recommendation: Replace text with: 5. AS-AWTS refers to activated sludge aerated wastewater treatment system

36 Table 7.1 [p. 64] Notes: 10. The level of disinfection and reduction in indicator organisms is dependent upon the level of and type of disinfection and is reliant on regular monitoring and maintenance.

There is repetition here.

Recommendation: Replace text with: 10. The level of reduction in indicator organisms is dependent upon the level of and type of disinfection and is reliant on regular monitoring and maintenance.

37 Section 7.2.1 [p. 64] The septic tank is typically used either to provide primary treatment prior to discharge into the ground via an infiltration system or to provide primary treatment prior to secondary treatment stage.

The use of the term “infiltration system” is inconsistent with the fact that the same

term is used in the list of land disposal methods (see Item 25 above).

Recommendation: Replace text with: The septic tank is typically used either to provide primary treatment prior to discharge into the ground via a subsurface land application disposal system or to provide primary treatment prior to secondary treatment stage

TP58 3rd


10


38 Section 7.2.1 [p. 64] Provided it is adequately sized, in many cases it can also be the most effective single component of a treatment system.

This is a bit of an overstatement, and could be misleading, given that much of the

BOD passes through to the land application system for in-soil treatment.

Recommendation: Replace text with: Modern conventional septic tank units have larger capacity than in the past, and when fitted with effluent outlet filters they provide a most effective primary treatment unit prior to land disposal of effluent.

39 Section 7.2.1 [p. 64] A conventional septic tank is a simple solids settling and scum retention unit (Fig. 7.1A) in which the accumulating sludge -----

Recommendation: Editing: A conventional septic tank is a simple solids settling and scum retention unit (Fig. 7.1) in which the accumulating sludge -----

40 Section 7.2.1 [p. 65] These are required in all septic tank systems in the Auckland region and are discussed further in section 7.2.6.

Recommendation: Editing: These are required in all septic tank systems in the Auckland region and are discussed further in section 7.2.7.

41 Section 7.2.2 [p.66] Septic tank capacities for combined domestic wastewater flows (“all waste”), and for separated flows comprising toilets (“blackwater”), and kitchen, bathroom and laundry (“greywater”) wastewater are set out as informative recommendations in AS/NZS 1547:2000 [Ref 1], and the same information is reproduced here in Table 7.2.

Table 7.2 does not include reproduced information from AS/NZS 1547, but rather

abbreviated information.

Recommendation: Replace text with: Septic tank capacities for combined domestic wastewater flows (“all waste”), and for separated flows comprising toilets (“blackwater”), and kitchen, bathroom and laundry (“greywater”) wastewater are set out as informative recommendations in AS/NZS 1547:2000 [Ref 1]. A summary of the AS/NZS 1547 recommendations is included in Table 7.2.

42 Section 7.2.2 [p.66] Table 7.2 provides guidelines for determining the approximate septic tank capacity requirements for tanks serving dwellings.

Actually, Table 7.2 compares recommended capacity requirements for AS/NZS

1547 and the USEPA manual, and then sets out TP58 requirements for up to 4

bedrooms (and 6 persons). This provides the basis for the 7 year pumpout interval

set out in the Notes. No further guidance is provided for TP58 capacities up to the

220 l/c/day maximum daily flow allowances in Table 6.2, or for dwellings of 7 or

more bedrooms, or households larger than 6 persons.

Recommendation: Replace text with: Table 7.2 compares AS/NZS 1547 and USEPA manual recommendations on septic tank capacity, and sets out TP58 requirements for tank capacities for dwellings.

43 Table 7.2 [p.67] Notes: 1. TP58 tank size calculation is based on sludge accumulation rate of 80 litre per person per year, a pump out frequency of seven years and 24 hour retention time for peak daily flow volume, using 200 litres per person per day. (This provides a buffer hydraulic retention capacity for pulse flows. A lower per person per day flow volume allowance does not provide such capacity and should not be used.)

This Note is not well worded, and is duplicated by Note 3 to some extent. To avoid

confusion with per person daily flow allowances, we need to only refer to settling

capacity allowances, and let Note 3 explain the relationship between the two (see

Item 44 below).

Recommendation: Replace text with: 1. TP58 tank capacity is based on sludge accumulation rate of 80 litres per person per year, a pump out frequency of seven years, and a setting capacity allowance of 200 litres per person. The minimum all waste tank size of 4,500 litres is based on a 4 bedroom dwelling accommodating up to six persons. For a larger dwelling, or for increased occupancy over six persons, the tank size should be increased accordingly or alternatively the tank should be pumped out more frequently.

TP58 3rd


11


44 Table 7.2 [p.67] Notes: 3. Tank capacity allowance of 200 litres/person for all waste tanks is greater than the per capita daily flow allowances to provide for hydraulic buffering. For greywater, the design capacity is 33% greater to compensate for the same flow intensities as the larger all waste tanks.

This Note can be amplified as it essentially repeats material from original Note 1.

Recommendation: Replace text with: 3. Tank capacity allowance of 200 litres/person for all waste tanks is greater than the per capita daily flow allowances to provide for hydraulic buffering. This buffering smoothes out peak flow intensities during high water use activities in the dwelling. For greywater, the design capacity is 33% greater to compensate for the same flow intensities as the larger all waste tanks.

45 Table 7.2 [p.67] Notes: 4. TP58 tank volumes are based on a tank including an outlet filter. Larger tank volumes are necessary with an outlet filter so that there is less hydraulic load on the filter surface.

This statement does not make sense. Hydraulic load on the filter surface has nothing

to do with tank volume. Presumably what is trying to be conveyed here is that larger

tank volumes provide greater hydraulic buffering during peak water use events in

the dwelling, and therefore provide lower hydraulic peak load on the filter surface.

However, this is not a key element in filter use. TP58 already recommends that

effluent outlet filters be added to existing small capacity septic tanks. What happens

here is that the clogging on the filter surface holds back flow, making water levels in

the tank rise slightly under peak flow, and thus automatically assist hydraulic

buffering.

Recommendation: Replace text with: 4. TP58 conventional septic tanks are in all cases to be fitted with an effluent outlet filter, including all waste, blackwater and greywater tanks.

46 Table 7.3 [p.68] Settling Volume Allowance (litres/person/day)

The settling allowance is a volume per person, not a volume per person per day.

Recommendation: Replace heading with: Settling Volume Allowance (litres/person)

47 Table 7.3 [p.68] Greywater 36 Hours Settling Volume Allowance Recommendation: Editing: Greywater 32 Hours Settling Volume Allowance

48 Table 7.3 [p.68] Greywater 160 40 320 Recommendation: Editing: Greywater 160 40 360

49 Table 7.3 [p.68] Notes:

Greywater septic tanks: 32 hours settling plus hydraulic buffering volume at a capacity allowance of 160 litres per person

per day, -----

The hydraulic buffering is included within the 32 hours.


Greywater septic tanks: 32 hours settling inclusive of hydraulic buffering volume at a

capacity allowance of 160 litres per person per day, -----

50 Section 7.2.4 [p. 69] The total scum/sludge accumulation allowance is assessed by taking the total wastewater flow per day and dividing it by the appropriate per person flow allowance for households in Table 6.2.

This statement needs clarifying.

Recommendation: Replace text with: The determination of equivalent persons for use in sizing the total scum/sludge accumulation allowance is assessed by taking the total wastewater flow per day and dividing it by the appropriate per person flow allowance for households in Table 6.2.

51 Table 7.4 [p.70] Source: [Ref 2] and [Ref 5] Recommendation: Editing: Source: [Ref 2] and [Ref 3]

52 Section 7.2.6 [p. 71] Grease Trap Design Most grease traps have in the past ----- multi chambered tanks improve efficiency.

Mention should be made of the availability of commercial effluent outlet filters

designed specifically for use in grease interceptor tanks.

Recommendation: Add text as follows: Most grease traps have in the past ----- multi chambered tanks improve efficiency. The availability of commercial effluent outlet filters (see also section 7.2.7) designed for grease interceptor tanks provides for improved control of grease from restaurant kitchen waste flows.

TP58 3rd


12


53 Section 7.2.7 [p. 72] Outlet filters can be placed within some three general configuration categories as is schematic diagram shown in Fig 7.3: - Type A: Single or multiple mesh tubes. - Type B: Single or multiple slotted tubes. - Type C: Multiple plate disc-dam module.

Because only Types A and C are shown in Figure 7.3, suggest a change in text.

Recommendation: Replace text with: Outlet filters can be placed within some three general configuration categories: - Type A: Single or multiple mesh tubes (see Figure 7.3). - Type B: Single or multiple slotted tubes. - Type C: Multiple plate disc-dam module (see Figure 7.3).

54 Section 7.2.10 [p.75] As discussed in Section 7.2.6, experience with the more recent larger septic tanks that have effluent outlet filter solids control device, ------

Recommendation: Editing: As discussed in Section 7.2.7, experience with the more recent larger septic tanks that have effluent outlet filter solids control device, ------

55 Section 7.3.1 [p. 77] Aerated wastewater treatment plants AWTP and ATP

Continuous flow, suspended growth aerobic systems CFSGAS [Ref 5]

ATP is a separate term now recommended be deleted (see Item 31 above). [Ref 5]

is incorrect again.

Recommendation: Replace text with: Aerated wastewater treatment plants AWTP.

Continuous flow, suspended growth aerobic systems CFSGAS [Ref 3]

56 Section 7.3.1 [p.77] For this NZ design manual a distinction has been made as follows:

AS-AWTS (activated sludge – aerated wastewater treatment system) for the suspended growth reactor unit;

BF-AWTS (biofilter – aerated wastewater treatment system) for the fixed growth(with submerged media) reactor unit;

TF-AWTS (trickling filter - aerated wastewater treatment system) for the fixed growth reactor unit.

A fundamental misunderstanding of the terminology and practice related to

secondary treatment systems appears to have crept in here. First, all modern

activated sludge (suspended growth) aerated treatment units now incorporate fixed

growth media. So the AS-AWTS and BF-AWTS as defined herein are the same

unit. Second, the term “biofilter” has replaced “trickling filter” in modern

wastewater treatment terminology [indeed, the second paragraph of this section

correctly refers to “trickling filter” (or biofilter)]. The use of “biofilter” herein to

refer to an activated sludge system with submerged media is thus totally incorrect.

Hence, there are only two categories which are applicable. [See also Item 31

above.]

Recommendation: Replace text with: For this NZ design manual a distinction has been made as follows:

AS-AWTS (activated sludge – aerated wastewater treatment system) for the suspended growth (usually incorporating submerged fixed growth media) reactor unit;

BF-AWTS (biofilter – aerated wastewater treatment system) for the non-submerged fixed growth media reactor unit.

57 Section 7.3.2 [p.77] A typical unit will incorporate a primary treatment septic tank with the overflow transferred to the aeration compartment by an outlet tee that may incorporate an outlet filter (see Section 7.2.8 above).

Recommendation: Editing: A typical unit will incorporate a primary treatment septic tank with the overflow transferred to the aeration compartment by an outlet tee that may incorporate an outlet filter (see Section 7.2.7 above).

TP58 3rd


13


58 Section 7.3.2 [p.77

and 78]

A typical unit will incorporate a primary treatment septic tank with the overflow transferred to the aeration compartment by an outlet tee that may incorporate an outlet filter (see Section 7.2.8 above). Air is supplied for aeration and mixing of the suspension of activated biological slimes by either a blower and sparge pipe, or a rotating impeller/aspirator unit. The overflow from the aeration compartment is then passed to a settling compartment for suspended sludge recovery and return before the final treated effluent enters a pump well for distribution to a land application system. Some units replace the settling chamber with an outlet filter to pass final effluent from the aeration chamber direct to the pump well. Blower driven aeration systems also provide air for air-lift pumps to transfer recovered biological sludge back to the aeration compartment and/or the septic tank. A skimming device on the settling compartment may also be used to return floating scum/sludge back for treatment in the septic tank. Impeller/aspirator aeration units may have a set of settling plates in the settling compartment for solids recovery, with a small solids pump to recycle sludge to the aeration compartment, or dispose of it to the septic tank. Variations of the AS-AWTS include SBR (sequencing-batch-reactor) units which operate in a fill and draw operational mode with recycle to achieve both biological treatment of organic matter as well as nutrient stripping of nitrogen products, specifically nitrates. In another variation, the aeration compartment may contain modules of submerged plastic media to assist in developing a submerged fixed film with the objective of providing better biological stability to the treatment process.

In accordance with the recommendation in Item 56 above, it is necessary to amend

this whole section.

Recommendation: Replace text with: A typical unit will incorporate a primary treatment compartment (or septic tank) with the overflow transferred to the aeration compartment by an outlet tee that may incorporate an outlet filter (see Section 7.2.7 above). The aeration compartment in modern systems will contain modules of submerged plastic media to assist in developing a submerged fixed film with the objective of providing better biological stability to the treatment process. Air is supplied by either a blower and sparge pipe, or a rotating impeller/aspirator unit (Figure 7.4), and provides aeration of the suspended and fixed film biological slimes and mixing of the suspension of activated sludge solids. The overflow from the aeration compartment is then passed to a settling compartment for suspended solids recovery and return of settled biological sludge to the aeration compartment. Some settling compartments may incorporate settling plates to assist solids recovery. Some units replace the settling compartment with an outlet filter to pass final effluent from the aeration chamber direct to the pump well. Final treated effluent enters a pump well for distribution to a land application system Blower driven aeration systems also provide air for air-lift pumps to transfer recovered biological sludge back to the aeration compartment and transfer excess sludge to the primary compartment (or septic tank). A skimming device on the settling compartment may also be used to return floating scum/sludge back for treatment in the septic tank. Impeller/aspirator aeration units may have a small solids pump to recycle sludge to the aeration compartment, and to dispose of excess solids to the septic tank. Biological growth on the submerged media results in lower sludge production volumes than in the older type AS-AWTS without media. The biological stability inherent in the use of submerged media may provide particular advantage for places that have intermittent or seasonal occupancy. Variations of the AS-AWTS include SBR (sequencing-batch-reactor) units which operate in a fill and draw operational mode with recycle to achieve both biological treatment of organic matter as well as nutrient stripping of nitrogen products, specifically nitrates.

59 Section 7.3.3 [p.78] 7.3.3 BF-AWTS [Biofilter – Aerated Wastewater Treatment System]

Recommendation: In accordance with the recommendation of Item 56, and in light

of the changes recommended in Item 58, delete the whole of this section 7.3.3, and

renumber following sections 7.3.4 to 7.3.8 accordingly to become 7.3.3 to 7.3.7.

Note that an amended version of the last paragraph of this section has been carried

into 7.3.2 (Item 58 above, second last paragraph).

60 Section 7.3.4 [p. 79] 7.3.4 TF-AWTS [Trickling filter – Aerated Wastewater Treatment System]

Only the heading needs amending now, as the text fits OK with the new heading.

Recommendation: Replace heading as follows (note also the new numbering): 7.3.3 BF-AWTS [Biofilter – Aerated Wastewater Treatment System]

TP58 3rd


14


61 Section 7.3.6 [p. 79] Reported BOD and TSS output efficiency from well operated systems are BOD 10 – 50gm/m

3 and TSS 15 – 60gm/m

3. Some

studies have reported lower discharge quality (elevated contaminant levels) resulting from surge flows, variable loading and inadequate maintenance [Ref 5].

I have observed that mg/l has been used earlier in this document (Table 7.4), and

that here gm/m3 is used. Note that [Ref 5] is still being used when [Ref 3] is correct.

Recommendation: Editing: (a) Reported BOD and TSS output efficiency from well operated systems are BOD5 10 – 50g/m

3 and TSS 15 – 60g/m

3. Some studies have reported lower discharge quality (elevated

contaminant levels) resulting from surge flows, variable loading and inadequate maintenance [Ref 5].

(b) Change mg/l to g/m3 in Table 7.4, page 70.

62 Section 7.3.6 [p. 80] Due to their special tuning needs, all AWTSs require on a consistent basis by an experienced operator, Operation and Maintenance (O&M) contracts are critical and are a condition of regulatory approval for use of AWTSs.

This sentence requires editing.

Recommendation: Replace text with: Due to their special tuning requirements, all AWTSs require inspection on a consistent basis by an experienced operator. Operation and Maintenance (O&M) contracts are critical and are a condition of regulatory approval for use of AWTSs.

63 Section 7.3.6 [p. 80] Further details of package plant operation and maintenance requirements are provided in Section 7.3.7.

This needs amending in two areas (but remember section numbering to be updated)..

Recommendation: Replace text with: Further details of AWTS operation and maintenance requirements are provided in Section 7.3.8.

64 Section 7.3.8 [p. 82] The activated sludge in suspension within the AS- AWTS is more sensitive to loading variations than the fixed film sludge in the TF- AWTS.

Consequential changes relative to Item 56 are required here.

Recommendation: Replace text with: The activated sludge in suspension within the AS- AWTS is more sensitive to loading variations (in spite of the stability associated with the submerged media) than the fixed film sludge in the BF- AWTS.

65 Section 7.3.8 [p. 82] AWTS units all have higher running costs to operate the aeration system than filter type systems.

This needs clarification. I presume the reference to “filter” is not to intermittent sand

filters, but to biofilters.

Recommendation: Replace text with: Activated sludge AWTS units all have higher running costs to operate the aeration system than biofilter type systems.

66 Section 7.4 [p.83] The effluent quality expected from advanced secondary treatment systems for the purpose of this manual (on the basis that wastewater will be discharged to land) is a biochemical oxygen demand (BOD) of better than 15mgO/l and a suspended solids (SS) level of better than 15mg/l.

The designation of BOD5 (not BOD) strength of mgO/l (or even gO/m3) is non-

standard (see also Item 61 above).

Recommendation: Replace text with: The effluent quality expected from advanced secondary treatment systems for the purpose of this manual (on the basis that wastewater will be discharged to land) is a biochemical oxygen demand (BOD5) of better than 15g/m

3 and a suspended solids (SS) level of better than 15g/m

3.

67 Section 7.4.3 [p. 87] Demand dose loading results in wastewater discharge onto the sand filter in a reduced number of doses concentrated around the time when it is produced in contrast to timer dosing which buffers wastewater produced during the day over 24 hours (see section 7.4.4).

This needs amending of section number.

Recommendation: Replace bracketed info with: (see section 7.4.5).

68 Table 7.7 [p. 88] Notes: 9. The above are guidelines from US literature [Ref 2 & 5].

Note that [Ref 5] is still being used when [Ref 3] is correct.

Recommendation: Replace bracketed info with: [Ref 2 & 3].

TP58 3rd


15


69 Section 7.4.4 [p. 90] FFTF can achieve a treated wastewater effluent quality of between that achieved by sand filters and extended aeration treatment plants.

Since “extended aeration” has not been used to any extent in the manual, change

accordingly.

Recommendation: Replace text with: FFTF can achieve a treated wastewater effluent quality of between that achieved by sand filters and activated sludge aeration treatment plants.

70 Section 7.4.4 [p. 90] Textile Filter Loading Rates Sand filter and textile filter wastewater treatment requirements are commonly assessed by a hydraulic loading rate that relates back to the areal loading of the filter media exposed surface area (surface loading rate) and expressed in litres per square metre per day (l/m

2/d). The surface area loading rate, in the case of sand filters,

takes the depth of sand, grain size and pore space between grains into account.

This whole section under sub-heading Textile Filter Loading Rates on pages 90 and 91

mixes up hydraulic loading rates between areal (horizontal) design loading rates (as

per Table 7.6 and 7.7), and media surface area loading in a manner that is quite

confusing. The treatment performance is related to what should be called the

“effective media surface area hydraulic contact rate”. Areal loading rates are

associated with design loading rates based on horizontal area of the media container.

Recommendation: Replace text with: Textile Filter – Treatment Mechanisms The effectiveness of biological treatment in sand filter and textile filter systems is a function of the effective surface contact area between applied effluent and the aerobic bacterial slimes growing on the sand or textile media, the hydraulic loading rate across the effective surface contact area, and the storage capacity for both bacterial slime and applied wastewater effluent within the void spaces in the media.

TP58 3rd


16


71 Section 7.4.4 [p. 91] The standard domestic textile filter footprint, excluding septic tank, recirculation tank and treated wastewater holding tank requirements is therefore variable. The surface area of the two systems currently available range from 0.5 – 1m

2 compared with a sand filter of about

10m2 required to treat an equivalent wastewater volume. Available

systems have different configurations, one having the textile housed in a pod on the top of the tank and another housing the textile within a basket inside the recirculation tank but suspended above the treated effluent surface water. Surface areal loading rates range from about 1,100 to about 2,100l/m2/d for domestic strength wastewater and domestic units can treat about 1,000 to 1,500 litres per day per unit.

Under Item 70 above, replacing the first paragraph (and sub-heading) under Textile

Filter Loading Rates sub-heading on page 90 means the text in the second, third and

fourth paragraphs fits reasonably well (although wherever “surface area” is used on

its own, this should be changed to “effective surface area”). However, from the top

of page 91 the text reverts to a discussion of “design loading rates” based on areal

(horizontal) surface areas, and a new sub-heading should be introduced here.

Recommendation: Add new sub-heading at top of page 91 as follows: Textile Filter – Loading Rates

However, of greater significance is the reference to two systems as being directly

comparable, these being illustrated in Figure 7.7 examples A and B. These are the

AdvanTex recirculating textile filter (based on over 10 years development work by

Orenco in the USA), and the Watercycle recirculating packed bed biofilter treatment

plant (based on a September 2003 prototype technology out of Dunedin). It is quite

inappropriate to treat these two systems as comparable textile filters – the

Watercycle system is in fact a BF-AWTS unit, not a textile filter. If Watercycle has

substituted textile chips or other material for the polystyrene bead used in the

September 2003 model, then there is even less reason to treat it as comparable with

the AdvanTex system until a proven track record is demonstrated. The developer of

Water Cycle has indicated in technical information that the unit is an example of the

AdvanTex type of treatment plant, and also states it is a development of

recirculating sand filter plants.

Given that :

(a) it does not use “textile” as the treatment media; and

(b) the unit is very much under development (compared to the large number of AS-

AWTS and BF-AWTS with long term use in NZ), then all references to it should be

withdrawn from this section of TP58. If so desired, mention could be made

elsewhere of it in the context of new developments.

Recommendation: Replace the text opposite with: At a design loading rate of around 1,000 l/m

2/d the currently available domestic textile filter

footprint is very small (at around 1m2) compared with a sand filter of about 10m

2 required to

treat an equivalent wastewater volume. As the unit can be sited on the septic tank and recirculation tank unit (Figure 7.7) the overall treatment system footprint is very compact.

72 Section 7.4.4 [p. 91] Foam filters are a separate type ---Surface loading rates for domestic effluent are of the order of 2100 l/m

2/day.

This 2100 l/m2/d design loading rate seems to contradict the statement regarding

foam filters being larger than textile, given the almost doubling of hydraulic load on

the top of the unit. Either justify this with further explanation in the text, or delete.

Recommendation: Delete: Surface loading rates for domestic effluent are of the order of 2100 l/m

2/day.

TP58 3rd


17


73 Section 7.4.4 [p. 92] Following in Figure 7.7 are two examples of textile filters available on the New Zealand market. Example A shows a textile filter located on top of a septic tank and recirculation tank. Example B shows the textile or foam filter located within the treatment tank unit.

For the reasons outlined in Item 71 above, this sentence and Example B in Figure

7.7 are inappropriate.

Recommendation: (a) Delete this text as the reference to Figure 7.7 is now covered in the change

suggested in Item 71 above.

(b) Delete Example B and related diagram in Figure 7.7, delete the words Example

A and retain the diagram of the AdvanTex unit.

74 Table 7.9 [p. 94] Table 7.9 Typical Performance Values ------

and the use of mg/l throughout the Table. Recommendation: Change “mg/l” to “g/m3” – see also Item 61 above.

75 Section 7.4.7 [p. 95] If intended for a holiday home, is the system stable under intermittent wastewater loading with long periods of no wastewater inflow? In the case of recirculating systems do the continue to recirculate when there is no wastewater flow to maintain conditions for bacterial activity? (Some systems are likely to take a while to stabilse during which period they could be odorous, so it’s important to ask how long this could take.)

This statement is borrowed from Section 7.3.7 related to “which AWTS to use”. The

reference to system being odorous during start-up or when running up to normal

load after a period of no-load I have not challenged for the AWTS system (though it

seems unlikely). However, for packed bed reactors generating odours during start-

up or running up to normal load after a quiet period, what evidence/information is

this based upon? Which systems compared to other systems, are more “likely to take

a while to stabilise”? Alternative wording may be appropriate here.

Recommendation: Change text as follows (includes editing matters related to the

original):

If intended for a holiday home, how does the system operate under intermittent wastewater loading with long periods of no wastewater inflow? In the case of recirculating systems do these continue to recirculate when there is no wastewater flow in order to maintain conditions for bacterial activity? How long until full treatment performance is achieved after resumption of normal wastewater flows?

76 Table 7.10 [p.96] Intermittent Sand Filter

Biochemical loading rate is also very important being typically 0.0025 – 0.01 kgBOD/m

3.

Editing required here (note that units are wrong).

Recommendation: Change text to:

Organic loading rate is also very important being typically 0.0025 – 0.01 kg BOD/m2.

77 Table 7.10 [p.96] Treated Wastewater Quality

Very effective at reducing faecal coliform level from 10 million CFU to less than 10,000 CFU/100mls claim less than 400 CFU/100mls.

The first point is that if FC are to be cited in terms of cfu/100mls (or CFU/100mls as

herein), should not the same units be used in Table 7.9 on page 94?

The second point relates to editing.


Very effective at reducing faecal coliform level from 10 million CFU to less than 10,000 CFU/100mls. Some systems are claimed to achieve less than 400 CFU/100mls.

78 Table 7.10 [p.96] Recirculating Sand Filter

Biochemical loading rate is also very important & typically 0.01 to 0.04 kgBOD/m

3.

Editing.


Organic loading rate is also very important & typically 0.01 to 0.04 kgBOD/m3.

79 Table 7.10 [p.97] RecirculatingTextile Filters

Typical hydraulic loading rates 1,700L/m2/d but typically less

than 1,700L/m2/d.

Can’t have two versions of what is “typical”. Note also that the units “L/m2/d” are

“l/m2/d” elsewhere (see page 91).


Hydraulic loading rates range from 1,100 to 2,100 L/m2/d, but are typically less than

1,700L/m2/d.

TP58 3rd


18


80 Section 7.5.2 [p.

99/100]

Primary Chamber Design Criteria The larger the primary treatment chamber, ---- and provide for better sludge quality and system health. The primary treatment chamber is the cheapest and most effective component of the ----- secondary treatment system. Extended primary treatment can also lead to aged primary wastewater and poor sludge quality.

These two consecutive paragraphs, one on page 99, the other on page 100, have

content that in some cases is contradictory, and in other case can be challenged.

(a) At the end of the first para we have reference to the benefits of large size being

“better sludge quality and system health”. This presumably refers to activated

sludge health in the secondary treatment chamber. However, the last sentence in the

second para completely contradicts this!

(b) At the beginning of the second para the reference to the primary treatment

chamber being the “cheapest and most effective component of the whole package

treatment system” seems to be a bit of an overstatement. The secondary treatment

component, whether an aeration chamber or sand/textile filter is the most effective

part of the treatment system. This is particularly so when coupled with good

biological solids containment associated with final clarification in the aerated

system, and the sand itself in the sand filter system.

Recommendation: Review and edit text.


100]

Required Primary Treatment Design Criteria: A. Minimum combined total retention capacity prior to secondary

treatment of at least 3 to 5 days --------- standards specified in 4A below and that less than 3 days primary treatment is sufficient.

It seems to me that the emphasis on having a large primary treatment chamber as

outlined in the para at the top of page 100 (as criticised above in Item 80) has been

carried through into here to become quite prescriptive. What is the basis for the 3 to

5 days average flow volume? By saying “minimum combined” does this mean 3 to

5 days of combined treatment plus 24 hour storage? Why is it that the final effluent

quality is so dependant on the size of the pre-treatment unit?

Recommendation: (a) Review and edit text to justify the prescriptive approach being taken.

(b) Note that the reference to “standards specified in 4A below” should be

“standards specified in D1 or D2 below”.


101]

More detail of these systems, including recommended design criteria for sizing of extended aeration package treatment systems, are provided in section 7.3 of TP58.

Section 7.3.5 [p. 79] deals with BOD loading ranges for extended aeration activated

sludge processes based on text book values and local manufacturers’ information.

However, they are very unspecific, so there is no actual recommendation on design

criteria for sizing extended aeration plants.

Recommendation: Review and edit text to remove this inconsistency. Replace with More detail of these systems is provided in section 7.3 of TP58.


101]

D.1. The quality of the final effluent from a AWTS ---- concentrations of 20 gO/m3 and ----.(As specified in point 13 below, a minimum ----- with these standards.)

Editing required, together with adding a preliminary statement to introduce D.1. [Note the 30gO/m

3 in the second para of D.1. which should be changed to 30 g/m

3. Note also

the incorrect use of gO/m3 (or mgO/l or mg/l) in 7.6.1 page 105, 7.7.4.3, page 114; 7.8.1.4,

page 118; 10.1.4, page 162; Table 10.1, page 162 and so on throughout the manual] Recommendation: Add to and edit text: Required Secondary Treatment Design Criteria: D.1. The quality of the final effluent from a AWTS ---- concentrations of 20 g/m

3 and ----. (As

specified in M below, a minimum ----- with these standards.)

TP58 3rd


19



101]

D2. The quality of the final effluent from an advanced secondary filtration treatment system ---- concentrations of 15 gO/m3 and ---.(As specified in point 13 below, a minimum ----- with these standards.)

Editing required, together with a preliminary sentence to introduce D.2.

Recommendation: Add to and edit text:

Required Advanced Secondary Treatment Design Criteria: D.2. The quality of the final effluent from an advanced secondary filtration treatment system ---- concentrations of 15 g/m3 and ----.(As specified in M below, a minimum ----- with these standards.)


102].

Final Treated Effluent Filter To achieve this limit, a disc filter or constant flush screen filter near the outlet of the plant, is frequently required depending on the performance of the treatment system, and ----- quality to the irrigation lines. Disc filters are usually constructed with aperture hole sizes of 120 microns in a well designed treatment system. ----- This is discussed further in Section 7.3.7 above.

From the second sentence opposite, this whole piece is not well worded. Disc filters

do not have aperture “holes”. Incorrect referral given to 7.3.7.

Recommendation: Edit text as follows: To achieve this limit a disc filter or constant flush screen filter is installed on the pressure line from the effluent pump to the drip irrigation system. The filter requirements are usually determined by the level of performance of the treatment system, and ----- quality to the irrigation lines. For a well designed treatment and irrigation system, disc filters with aperture sizes of 120 microns are usually provided. ----- This is discussed further in Section 7.3.8 above.


102/103].

Whole Section. In addition to Item 85 above, there are several editing matters related to punctuation

and wording that would improve this section.

Recommendation: Full professional editing required, not only for this section, but

for the whole of this edition of TP58.


103].

System Start up Inspection and Sample Analysis M. Within three months ----- of the final effluent in a sterilised sample vessel (minimum 1 litre).

Why a “sterilised sample vessel” when collecting for BOD5 and SS analysis?

Recommendation: Delete “sterilised”?


103].

System Start up Inspection and Sample Analysis M. If the first sample is not ----- TP58 (criteria D1 and D2 in section 7.3 or 7.4) for the type of system installed then sampling should continue and recent ----- design specifications for at least two consecutive samples.

(a) Editing.

Recommendation: Change referrals to “section 7.3 and 7.4” to “section 7.5.3 and

7.5.4”.

(b) Also note that the reference to continuation of sampling in this sentence is very

non specific – when should the second and third etc samples be taken? If the second

and third are OK they then meet the “at least two consecutive samples” requirement.

Recommendation: Add “weekly” into follow-up sampling frequency. ------type of system installed then weekly sampling should be carried out and recent -----.


104].

System Installation --- As stated in Sections 7.3.6 and 7.4.7 above, ----

Editing,

Recommendation: Change “7.3.6” to “7.3.7”.


104].

General System ----- Q. ----with the Management Plant ----.

Editing “Management Plan”.


105].

General The organic content of treated wastewater high in BOD5 and SS results (i.e. in a greater disinfection treatment high chlorine demand ------- in effective UV disinfection.

Editing.

Recommendation: Change to: The organic content of treated wastewater high in BOD5 and SS results in a greater disinfection treatment (i.e. high chlorine demand ------- in effective UV disinfection.

TP58 3rd


20


92 Section 7.7.2.2 [p.

112]

b. Decentralised systems It is unlikely to be practicable to install separate chlorinated and unchlorinated reuse systems from a decentralised wastewater treatment plant, if there are demands for different forms of reuse.

This statement is not justified by existing experience in NZ, as it is entirely

practicable to achieve recycle in a split system. At the Golden Valley Subdivision,

Kuaotunu near Whitianga on the Coromandel, the design flow through recirculating

sand filter is 28 m3/day of which 5.6 m

3/day is chlorinated and recycled for toilet

flushing. The remaining 22.4 m3/day unchlorinated flow is drip irrigated into a

landscaped tree planted area.

Recommendation: Change to: In some cases it can be practicable to install separate chlorinated and unchlorinated reuse systems from a decentralised wastewater treatment plant, if there are demands for different forms of reuse

93 Table 7.12 [p. 114] Notes Note that “Crites” is incorrectly spelt in two places as “Crities”.

94 Section 7.7.6.1 [p.

116]

7.7.6.1 Greywater Composition Nevertheless, it is necessary to be aware that greywater has been confirmed to have very high faecal coliform ------- wastewater i.e. in the order of 10

3 coliform bacteria per gram [Ref 13] and up to 10

6 to

107 coliform bacteria per gram [Refs 10 and 42] compared with 10

8

coliform bacteria per gram for typical combined wastewater.

Specifying faecal coliform concentrations in numbers per gram is surely meant to be

numbers in cfu/100mls. Ref 13 is a paper on composting of human waste where

numbers per gram could apply, but for greywater (as for any other liquid waste

flow), we use numbers per unit volume (100mls), not numbers per unit weight.

Recommendation: Review original sources to check out method of specifying

concentration, and make editing corrections as appropriate.

95 Section 7.7.6.3 [p.

117]

Where a homeowner wishes to reuse greywater ---- less treatment (than the level of standard wastewater treatment specified in Section 7.8.1 is necessary for greywater) may be allowable.

What is meant by this statement “less than the level of standard wastewater

treatment”?

Recommendation: Provide clarification as to potential less level of treatment.

96 Section 7.8.1.1 and

7.8.1.3 [p. 117]

7.8.1.1 Greywater Design Volume and 7.8.1.3 Greywater Treatment Due to the significant contaminant levels in ---- to reuse a portion of the treated wastewater flow.

The second and third sentences in the first paragraph of each of these sections are

almost identical. Why the repetition?

Recommendation: Delete these two sentences from 7.8.1.3, and close up text with

the para at top of page 118.

97 Section 7.8.1.3 [p.

118]

Due to the significant greywater contamination levels, as a minimum, advanced primary treatment is required. This should involve a septic tank sized to enable adequate solids separation and with an outlet filter to prevent gross solids carryover.

“Advanced primary treatment” does not appear to be defined anywhere in TP58.

The explanation of what it constitutes here in the second sentence in fact refers to

“conventional septic tank” in section 7.1, page 62.

Recommendation: If the term “advanced primary treatment” is to be used, define it

elsewhere, and use appropriately throughout TP58.

98 Section 7.8.2.2 [p.

119]

7.8.2.2 The Need for Greywater Treatment Further information on greywater treatment and disposal systems is provided in Section 7.7.6 and information on greywater reuse is provided in Section 7.8.1.

The reference section numbers are mixed up.

Recommendation: Edit to: Further information on greywater treatment and disposal systems is provided in Section 7.8.1 and information on greywater reuse is provided in Section 7.7.6.

99 Section 7.8.2.3 [p.

119]

7.8.2.7 Types of Composting Systems The smaller compost is often walled off from the bathroom -----.

Missing word.

Recommendation: Edit to: The smaller compost toilet is often walled off from the bathroom -----.

100 Section 7.8.2.3 [p.

120]

Dry bucket toilets – limited treatment is by use a dry soak material.

What does this mean?

Recommendation: Clarify and rewrite.

TP58 3rd


21


101 Section 7.8.2.4 [p.

120]

7.8.2.4 Design Features of Composting Systems The composting unit must be designed ----- faecal coliform level of less than 200MPN (or CFU) per gram [Ref 11].

AS/NZS 1546.2:2001 states that the bacterial performance requirement is “less than

200 faecal coliforms per gram dry weight”.

Recommendation: Edit to: The composting unit must be designed ----- faecal coliform level of less than 200MPN (or CFU) per gram dry weight [Ref 11].

102 Section 7.8.2.4 [p.

120]

The special features of composting toilet systems depend on the system type and can include dry vaults (pit privies and composting toilets), wet vaults (nonflush or lowflush sytems) and a range of selfcontained toilet systems (dehydrating and incineration toilets, chemical toilets). Proprietary systems such as composting and other self contained toilets systems are sized -----.

These two sentences do not make sense. All the other toilet systems referred to are

not variations of composting systems.

Recommendation: Change text to: The special features of composting toilet systems depend on the system type and can include semi-flush units and urine separation units. Proprietary composting systems are sized -----.

103 Section 7.8.2.4 [p.

120]

United State standards governing the minimum ------ :Nonliquid Saturated Treatment Systems”.

Why refer to the US requirements when we have our own Australia/New Zealand

joint Standard.

Recommendation: Replace text with: Australian and New Zealand standards governing the minimum materials, design, construction and performance of composting toilet systems is AS/NZS 1546.2:2001 “On-site domestic wastewater treatment units – Part 2: Waterless composting toilets”.

104 Section 7.8.2.4 [p.

121]

7.8.2.4 Conditions Required for Effective Composting Section number should be 7.8.2.5.

Recommendation: Amend Section numbering from here on through all 7.8.2 sub-

paras.

105 Table 7.13 [p. 121] Table 7.13: Carbon to Nitrogen Ratio in Organic Materials What is the meaning of the asterisk alongside “(Weight to weight)” in the second

column?

Recommendation: Add qualification/note associated with the asterisk, or delete

asterisk.

106 Table 7.14 [p. 122] Advantages of Composting Toilets Reduced quantity and strength of wastewater to be disposed of on-site, and the size of the land disposal system.

Wording not clear.

Recommendation: Change text to: Reduced quantity and strength of wastewater to be disposed of on-site, and reduced size of land disposal system.

107 Table 7.14 [p. 122] Disadvantages of Composting Toilets Removing the final product is an unpleasant job, particularly if the system is properly installed, operated and maintained.

What an odd statement! The better the system is installed etc, then the more

unpleasant is the removing of final product? I think not!

Recommendation: Change text to: Removing the final product can be an unpleasant task, even though the system is properly installed, operated and maintained.

108 Table 7.14 [p. 122] Disadvantages of Composting Toilets Most require some power source (to assist with ventilation and/or mixing).

When is power required for mixing (via some sort of motorised system?). “Most”

require power? I think not.

Recommendation: Change text to: May require a power source to assist with ventilation.

109 Section 7.8.2.6 [p.

123]

7.8.2.6 Risks from Use and Maintenance of Composting Systems

Mature compost ---- fresh waste, though filtration -----.

Editing (and remember renumber to 7.8.2.7).

Recommendation: Change to:

Mature compost ---- fresh waste, through filtration -----.

TP58 3rd


22


110 Section 7.8.2.7 [p.

125]

iii. Reduce risk of Ingestion

Bury compost for at least ---- in contact with any consumable plants for surface waters, prior -----.

Editing.

Recommendation: Change to: Bury compost for at least ---- in contact with any consumable plants or surface waters, prior ----.

111 Section 7.8.2.7 [p.

125]

Other more general maintenance requirements include: vii. (This is discussed further in Section 7.8.2.4 iv.)

Editing.

Recommendation: Change 7.8.2.4 iv to 7.8.2.5 iv (see Item 104 above). Carry

renumbering through in xi below, and change 7.8.2.8 to 7.8.2.9.

112 Section 7.8.2.8 [p.

126] 7.8.2.8 ARC Regulations for On-site Composting Systems Wherever the design wastewater flows ----the disposal system reserve area must be increased by an additional 40 to 50%.

Item 21 above suggests changes to the single * note in Table 5.3. To be consistent

with this change here, we need to change the text.

Recommendation: Change text to: 7.8.2.9 ARC Regulations for On-site Composting Systems Wherever the design wastewater flows ----the disposal system reserve area must be 140 to 150%.

113 Section 7.8.3.1 [p.

126]

7.8.3.1 Design Features of Vermiculture Systems The use of a vermiculture system does not remove the requirement for standard treatment of the liquid wastewater (black and greywater, ---- these guidelines (refer Section 7.8.1).

7.8.1 deals only with greywater.

Recommendations: Either:

(a) Delete “(refer Section 7.8.1)”; or

(b) Add text so to read “(refer Sections 7.2 to 7.4 and 7.8.1)”.

114 Section 7.8.3.1 [p.

126/127]

The liquid flow from a vermiculture system is considered equivalent to advanced primary treated wastewater and needs to be disposed of according to relevant guidelines above and regulations.

What is meant by “advanced primary treatment?

Recommendation: Adopt the Recommendation under Item 97 above.

115 Section 7.8.3.2 [p.

127]

7.8.3.2 Maintenance Requirements of Vermiculture Systems Follow through numbering changes as per Item 104 above.

Recommendation: Change Section 7.8.2.6 and 7.8.2.7 to 7.8.2.7 and 7.8.2.8

respectively.

[Note the use of “coply” instead of “comply” in the last para of this section.]

116 Section 7.8.3.3 [p.

127]

7.8.3.3 ARC Regulations for On-site Vermiculture Toilets In accordance with the requirements for more generic composting toilets in Section 7.8.3.2, whenever -----.

Incorrect referral.

Recommendations: (a) Change 7.8.3.2 to 7.8.2.9 (where renumbering in accordance with Item 104

above is implemented).

(b) Implement Recommendation in Item 112 also for the text here.

117 Section 7.8.4.1 [p.

128]

7.8.4.1 General Design criteria for and performance results for the pilot plant have been published [Ref 27].

This sentence is a repeat of the same sentence in the middle of the first para in this

subsection, but this time uses an incorrect reference (Ref 27 is related to mound

design). The pilot plant work is now out of date, as at On-site 01 the field visits took

us out to see several prototype treatment systems in a village north of Armidale.

Peat bed treatment in Australia has thus progressed beyond the material cited in

respect of Ref 28.

Recommendations: (a) Delete this sentence.

(b) Replace it with: Further to the pilot plant results published in Ref 28, prototype units have been installed and are operating successfully in Australia since 2001.

TP58 3rd


23


118 Section 7.8.5.1 [p.

129]

Guidelines used in the United States for designing wetlands are provided in the USEPA “Manual for Constructed Wetlands – Treatment of Municipal Wastewater “ [Ref 15]. The USEPA Manual (part 1.6) introduces a number ----.

This reference to the USEPA wetland design manual in the context of on-site

domestic wastewater management seems rather misplaced. There are several design

manuals produced by US State Agencies dealing specifically with on-site

wastewater wetland system. The Tennessee Valley Authority was the first State

agency to get into on-site wetland design guidelines in 1988 (second edition in

1993), and much of subsequent design manual advice has been based on their work.

In addition, extensive work over some 10 years into on-site wastewater constructed

wetlands has been undertaken (and well reported) by researchers at Southern Cross

University in Lismore NSW.

Recommendation: Change and include additional text: General guidelines used in the United States for designing wetlands are provided in the USEPA “Manual for Constructed Wetlands – Treatment of Municipal Wastewater “ [Ref 15]. In addition, a number of agencies have produced design guidelines specific to on-site wastewater systems. Many of these have been based on the early work in this area by the Tennessee Valley Authority which produced the first guidelines for small wastewater flows including individual residences in 1988, updated in 1993. The USEPA Manual (part 1.6) introduces a number ----.

119 Section 7.8.5.4 [p.

131]

A summary article by Mr Chris Tanner in ------. Incorrect title for Chris Tanner.

Recommendation: Change to: A summary article by Dr Chris Tanner in ------.

120 Section 7.8.5.5 [p.

131]

7.8.5.5 On-site Wetland Systems Small scale on-site constructed subsurface wetland systems are available for used on-site systems have been developed for the New Zealand situation. ----This advantage is likely to be severely reduced in winter and lost in wet weather where stormwater also collects in the treatment system, as it does in a sand filter system.

Poor wording in these two sentences. Stormwater does not get onto wetlands or sand

filters, only incident rainwater.

Recommendation: Change to: Small scale constructed subsurface wetland systems available for use for on-site domestic wastewater management have been developed for the New Zealand situation. ----This advantage is likely to be reduced in winter due to lower evapo-transpiration rates, and also affected in wet weather due to incident rainfall, as also occurs with a sand filter system.

121 Section 8.5.3 [p.

137]

8.5.3 Automatic Sequencing Valves Where sufficient head from pump or siphon dosing is available, automatic sequencing valves can be utilised, reducing dependence on the manual operation of hand operated valve units.

This is not the reason that automatic sequencing valves are used. They are used to

replace flow splitting manifolds feeding a series of parallel distribution lines.

Recommendation: Change to: Where sufficient head from pump or siphon dosing is available, automatic sequencing valves can be utilised to replace distribution manifolds, enabling design certainty in ensuring that equal flow distribution is achieved to a set of parallel trenches or beds. The hydraulic design of distribution manifolds has to be supported by careful installation and fine tuning during commissioning testing in order to confirm equal loading of all elements of the system. Automatic sequencing valves, by their very design and operation, eliminate the disadvantages associated with manifold systems.

TP58 3rd


24


122 Section 8.5.4 [p.

137]

8.5.4 Distribution Manifolds Proprietary distribution manifolds are available for loading controlled distribution systems and also allow diversion of flow if resting of a sector is required.

You do not purchase manifolds off the shelf. They have to be specifically designed

for each application.

Recommendation: Change to: Distribution manifolds are utilised for pressure dosing of laterals feeding individual sectors of a land application system. Careful design of both the manifold and the laterals is required to ensure that uniform dose loading of the system is achieved (see Section 8.6.3 below).

123 Section 8.5.6 [p.

138]

8.5.6 Drop Box Loading In all cases pressurised distribution by pump to ensure even distribution over the maximum area is now considered more appropriate.

This sentence is confusing being thrust in here in this manner – this point has been

well made elsewhere in section 8.2.

Recommendation: Delete and then add: In any case, the preferred method of loading is pressure dosing via sequencing valves or manifolds to ensure even distribution over the full design surface (see Section 8.2 introduction above).

124 Section 8.6.3 [p.

139]

8.6.3 Low Pressure Pipe Loading [LPP & LPED] This section and the following Section “8.6.4 LPED [Low Pressure Effluent

Distribution]” need amalgamating and tidying up. There is no need to have two

sections here, as the 8.6.4 content is essentially duplicating information in 8.6.3. We

also need to differentiate between LPED dose loading and LPED irrigation systems.

Recommendations: (a) Change title of section to: 8.6.3 Low Pressure Dose Loading [LPP & LPED]

(b) Delete whole section 8.6.4 LPED [Low Pressure Effluent Distribution] on page 140.

125 Section 8.6.3 [p.

139]

8.6.3 Low Pressure Pipe Loading [LPP & LPED] In situations where flood loading is neither practical nor suitable (for example Category 1-3 soils) a perforated pressure line system loaded by pump or siphon is an alternative for spreading effluent evenly over the full design area. This method is suitable for both free draining and slowly draining soils. LPP (low pressure pipe) and LPED (low pressure effluent distribution) are essentially the same. The difference between the two is that an LPED pressure line is inserted (nested) within draincoil distribution line and a LPP line is not. Where LPED is used for free draining soils it is considered a distribution method to ensure applied wastewater is distributed onto the entire design basal application area in which case design is based on the land disposal method and not LPED areal loading design procedure. Where used in moderate to slowly draining soils LPED is used to distribute the wastewater within a shallow trench and design loading determined on an areal basis.

This paragraph needs to be amended to give effect to the comments and

recommendations in Item 124 above.

Recommendation: Change text to: 8.6.3 Low Pressure Pipe Loading [LPP & LPED] Application and Function In situations where flood loading is neither practical nor suitable (for example Category 1-3 soils) a perforated pressure line system loaded by pump or siphon is an alternative for spreading effluent evenly over the full design area. This method is suitable for both free draining and slowly draining soils. LPP (low pressure pipe) and LPED (low pressure effluent distribution) are essentially the same. The difference between the two is that an LPED pressure line is inserted (nested) within draincoil distribution line and a LPP line is not. LPED was originally developed for distribution in free draining soils where LPP provides ineffective loading of the design basal area due to the spot loading that occurs at each perforation (squirt hole). In converting LPP into LPED by nesting the LPP dose line within draincoil, the discharge from each squirt hole is then “sloshed” along the invert of the draincoil to spread relatively evenly along the length of the line. This avoids the spot loading effect of LPP, and provides for more effective effluent distribution over the full design basal area. LPP and LPED are also used as the distribution system for subsurface irrigation of septic tank effluent via LPP subsurface irrigation (Section 9.3) as well as LPED subsurface irrigation and LPED surface trickle irrigation (Sections 9.4 and 9.5).

TP58 3rd


25


126 Section 8.6.3 [p.

139]

Sizing the Dose Volume The size, number and spacing of discharge orifices in each distribution lateral cannot be designed by a rule-of-thumb if the laterals are to be evenly loaded.

This whole section actually gives no guidance on how to “size” the dose volume.

Recommendation: Add text as follows: The size, number and spacing of discharge orifices in each distribution lateral cannot be designed by a rule-of-thumb if the laterals are to be evenly loaded. However, the rule of thumb for sizing the dose volume is that a minimum dose of 10 times the volume capacity of the distribution manifold and laterals is required in order to build up adequate back pressure in the system so as to achieve uniform distribution to all lateral perforations (squirt holes).

127 Section 8.6.3 [p.

140]

Some designers have adopted 5.0 mm, 4.0 mm or 3.0 mm diameter perforations. It is important that a squirt height of 1.5metres is achieved at each outlet orifice to maximise self scouring. The hydraulic calculations should be undertaken by design specialists. Commercial computers software programmes are available for such calculations. Each lateral can either be loaded individually via a sequencing valve so long as sufficient head is available to trigger rotation or alternatively the entire lateral network can be loaded with each dose. Where the entire lateral network is dose loaded it is important that each lateral is loaded equally and discharge not concentrated into the lowest trenches and can be achieved by placing a flow control plate at the start of each lateral. The orifice size can only be calculated when the height of each lateral, length and number of outlet orifices are known and ensures even loading although individual trenches may be of variable length and elevation. A non-return valve at the start of each line ensures the higher elevation laterals do not drain to the lowest laterals between doses and overload the lower lines

This paragraph here hides away a reference to automatic sequencing valves within

the discussion which so far has been all about manifold system design.

Recommendation: Reorganise into two paragraphs, and amend/add text:: Some designers have adopted 5.0 mm, 4.0 mm or 3.0 mm diameter perforations. It is important that a squirt height of 1.5metres is achieved at each outlet orifice to maximise self scouring. The hydraulic calculations should be undertaken by design specialists. Commercial computers software programmes are available for such calculations. Where the entire lateral network is dose loaded it is important that each lateral is loaded equally and discharge not concentrated into the lowest trenches and can be achieved by placing a flow control plate at the start of each lateral. The orifice size can only be calculated when the height of each lateral, length and number of outlet orifices are known and ensures even loading although individual trenches may be of variable length and elevation. A non-return valve at the start of each line ensures the higher elevation laterals do not drain to the lowest laterals between doses and overload the lower lines As an alternative to manifold pressure distribution, each lateral can be loaded individually via an automatic sequencing valve (Section 8.5.3). The dose volume for an individual lateral can be based upon the total daily flow divided by the number of laterals. With “on demand” pumping controlled by float switches set to the daily dose volume for each lateral, then each sector of the land application area (such as an individual trench) receives a single daily dose over a period of minutes, thus allowing the effluent to contact “rested” soil and be treated during the remaining 24 hours minus the dose time.

128 Section 8.6.3 [p.

140]

Once the lines are installed and before they are covered, the system must be fully tested with clean water so that the effectiveness of the dosing system, orifice outlet ---------.

This paragraph starts into a new topic area, and should be sub-headed accordingly.

Recommendation: Add sub-heading and highlight “before”: Commissioning Once the lines are installed and before they are covered, the system must be fully tested with clean water so that the effectiveness of the dosing system, orifice outlet ---------.

129 Section 8.6.3 [p.

140]

All distribution lines must be capped or screw plugged with removable end pieces to enable maintenance in case of line blockage. Any growth which could clog --------.

This paragraph starts into a new topic area, and should be sub-headed accordingly.

Recommendation: Add sub-heading: Maintenance All distribution lines must be capped or screw plugged with removable end pieces to enable maintenance in case of line blockage. Any growth which could clog -------.

130 Section 8.6.4 [p.

140]

8.6.4 LPED [Low Pressure Effluent Distribution] Recommendation: In line with Item 124 above, delete this whole section.

TP58 3rd


26


131 Figure 8.1 [p. 141] Figure 8.1 Perforation Details for Distribution Lines in Rigid PVC

There is a configuration table associated with the “saws cuts” diagram which has

been omitted.

Recommendation: Add configuration table under “Saw Cuts” diagrams as follows:

Configuration Width Spacing 6 mm 100 mm 150 mm 8 mm 130 mm 200 mm

132 Section 9.1 [p. 144] 9.1 SUBSOIL SOAKAGE – GENERAL The objective of the land disposal systems is to provide ----- ponding within the land disposal area will not result in effluent breakout. Actual acceptance rates will be ---- uptake of nutrients into vegetation biomass, and transpiration thereby minimising effects on groundwater. In all design situations, the requirements for separation distances to surface and groundwater as set out in Table 5.2 should be maintained. Following are the irrigation methods covered in this section below.

Pressure Compensating Dripper Irrigation (PCDI).

Low Pressure Pipe Subsurface Irrigation (LPP)

Low Pressure Effluent Distribution Irrigation System (LPED)

LPED Subsurface Trickle Irrigation.

LPED Surface Trickle Irrigation.

These first two paragraphs are fine as a general introduction, but there is a lot of

other general introductory material related to irrigation systems set out over in 9.3.1

on pages 150/151 that rightly belongs here. In addition, the last paragraph duplicates

material in 9.3.1 at the bottom of page 150 (See Item 138 below).

Recommendation: Reorganise this material into separate subsections, adding in

material from 9.3.1, and correcting the list of systems covered as follows: 9.1 SUBSOIL SOAKAGE 9.1.1 General The objective of the land disposal systems is to provide ----- ponding within the land disposal area will not result in effluent breakout. Actual acceptance rates will be ---- uptake of nutrients into vegetation biomass, and transpiration thereby minimising effects on groundwater. In all design situations, the requirements for separation distances to surface and groundwater as set out in Table 5.2 should be maintained. 9.1.2 Irrigation methods The following irrigation methods are covered in Sections 9.2 to 9.6 below. Pressure Compensating Dripper Irrigation (PCDI) – secondary effluent.

Low Pressure Pipe Subsurface Irrigation (LPP) – primary effluent.

Low Pressure Effluent Distribution Irrigation System (LPED) – primary effluent.

LPED Surface Trickle Irrigation – primary effluent.

Spray Irrigation – tertiary effluent.

[Continued]

TP58 3rd


27


132

[c’td]

Section 9.1 [p. 144]

(continued)

[Continued] 9.1.3 Application of Irrigation Systems Irrigation systems involve the ultimate in the “KISS” approach to land application of treated effluent. Distribution into (and in some cases onto) the soil over a broad design area is undertaken on the basis of “areal” loading. Irrigation systems are particularly suited to Category 4 to 5 soils, where clay ---- is the preferred irrigation method for Category 5 and 6 soils. However, their use for other soil Categories is a valid design option where environmental requirements can be met. It is essential that a minimum depth of 250mm ----- assimilation of the applied wastewater. Further details on the construction and installation of LPP and LPED irrigation systems for primary treated effluent are provided in Sections 9.3 and 9.4 [Note: LPP and LPED dosed loading methods for trenches and beds are discussed in 8.6.3 and 8.6.4 above.]

133 Section 9.2.1 [p.

144]

General Secondary treatment is usually provided via Aerated Treatment Plants (Figure 7.4) or Intermittent Sand Filter and Recirculating Sand Filter, Recirculating Textile Filter, Recirculating Trickling Textile Filter and Recirculating Foam systems (Figures 7.5, 7.6, 7.7 & 7.8).

Because of the changes in terminology and content associated with Items 59/60 and

73 above, we need to make changes here.

Recommendation: Change text as follows: Secondary treatment is usually provided via Aerated Treatment Plant (Figure 7.4) or Biofilter Treatment Plant, or Intermittent Sand Filter, Recirculating Sand Filter and Recirculating Textile Filter (Figures 7.5, 7.6, & 7.7).

134 Section 9.2.3 [p.

146]

9.2.3 Areal loading rates for pressure compensating drip irrigation The areal loading rate is determined according to soil characteristics and environmental constraints with lower rates adopted for sites having environmental limitations. Typically the maximum areal loading rate for Category 4 soils is 5mm/day with lower rates of 2 to 3mm/day being employed for Category 5, 6 and 7 soils. Higher loading rates (25 to 50mm/day) may be appropriate for Category 1 and 2 soils depending on the environmental constraints (including groundwater depth and any potential health risks). In the case of Category 1 soils the designer is reminded that PCDI becomes a distribution method for loading a discharge control trench (Category 1 soils) and must following the design guidelines for discharge control trenches using basal loading rates.

The requirement to use discharge control trenches loaded by PCDI is totally

inappropriate, and is discussed in detail in Items 136, 137 and 183 below. A change

in wording here is needed to achieve consistency with Item 137.

Recommendation: Change text as follows: The areal loading rate is determined according to soil characteristics and environmental constraints with lower rates adopted for sites having environmental limitations. Typically the maximum areal loading rate is 5mm/day for Category 1 and 2 soils, with lower rates of 4mm/day down to 2mm/day being employed for Category 3 to 7 soils. The areal loading rate is based upon irrigation into the topsoil where the secondary treated effluent is retained and treated further before portion infiltrates through into the subsoil, and portion evapo-transpires through plant/vegetation cover. The variation in loading rate recognises the capacity of the underlying soil to manage that portion which infiltrates below the topsoil layer.

135 Section 9.2.5 [p.

149]

---- 20gm/m3 and 30gm/m

3 (BOD5:SS). ----- Editing.

Recommendation: Change units: ---- 20g/m

3 and 30g/m

3 (BOD5/SS). -----

TP58 3rd


28


136 Section 9.2.5 [p.

149]

Lines are generally installed parallel at 0.3, 0.5 to 1 metre centres, however this can be varied according to the site conditions. Closer line spacing is appropriate where wastewater is reused to sub-irrigate lawns and within slowly draining category 4, 5 & 6 soils whereas wider spacing is appropriate on steeper slopes. Installation and loading rate details are summarised in Table 9.2 .

To take account of the changes recommended in Item 134 above, consequential

changes are required here.

Recommendation: Change text as follows: Lines are generally installed parallel at 0.3, 0.5 to 1 metre centres, however this can be varied according to the site conditions. Closer line spacing is appropriate where wastewater is reused to sub-irrigate lawns, within faster draining Category 1 and 2 soils, and within slowly draining Category 5 to 7 soils. Wider spacing is appropriate on steeper slopes. Installation and loading rate details are summarised in Table 9.2.

137 Table 9.2 [p. 150]

Design Areal Loading Rates Soil Category

1

35mm/d to 50mm/day [Note 1]

2 25mm/day [Note 2] 3 15mm/day to 20mm/day [Note 2 & 3]

[Dependent on environmental constraints] 4 5mm/day 5 3mm/day to 4mm/day [Notes 3 and 4] 6 2mm/day to 3mm/day 7 2mm/day or less

Notes: 1. Category 1 soil requires special design, such as installation of drainage control trenches under the irrigation lines. In this instance PCDI becomes a distribution method. 2. PCDI is a distribution method when used in Category 1, 2 & 3 soils. 3. The higher loading rates are only applicable where there is at least 50% reserve area. 4. Loading rates of up to 5mm/day may be appropriate in Category 5 sols where the depth of topsoil is 250mm or more. Effective distribution in lawns is best achieved using closely spaced lines and emitters (0.3m x 0.3m) and use of very conservative laoding rates of less than 3mm. The land disposal area and/or linear length of irrigation lines are to be adjusted when the line spacing is varied from 1.0m [Ref 17].

The requirement to utilise discharge control trenches for drip irrigation of secondary

effluent into Category 1 soils is quite inappropriate.

First, the use of discharge control trenches in Category 1 soils is a design method for

managing septic tank effluent discharges into such soils. The discharge control

trench is aimed at producing a secondary effluent quality with bacterial reduction

before the treated flow leaves the base of the trench into the natural soil. Given that

design rules for trenches (Section 10.1.4) in this TP58 cover special cases where

faecal coliform controls on both primary and secondary effluent are needed under

environmental constraints, then the designer is likely to adopt the most cost effective

option, and go for septic tank effluent into the trenches. Providing secondary

effluent into the trenches might only be worth the additional expense for a treatment

plant if some concession in terms of design loading rate into the trench could be

given (and the trench size consequently reduced). In addition, use of LPED dosing

makes better sense than use of drip line dosing for discharge control trenches.

Second, drip irrigation is directed into the topsoil over the Category 1 soils, and not

direct into the subsoil. Hence, the bacterial retention and reduction capacity of that

soil is a controlling feature on protecting the groundwater below from

contamination. The 5mm/day drip irrigation loading rate associated with Category 1

soils is discussed in the recommended amended text in Item 134 above. The higher

drip irrigation rates that appear to be adopted in the US have been set aside in

Australia and NZ to ensure in-topsoil treatment is effective. Hence 5mm/day (as per

AS/NZS 1547) is entirely appropriate. However, given the ARC environmental

concerns which has resulted in the specification of discharge control trenches for

drip in Category 1 soils, improvements could be made by spreading the effluent

more uniformly using 300mm x 300mm emitter and line spacing.

[Continued]

TP58 3rd


29


137

[c’td]

Table 9.2 [p. 150]

(comtinued)

Recommendation: Amend the Table and change text as follows: Design Areal Loading Rates Soil Category

1 & 2

5mm/day [Note 1]

3 4 to 5mm/day [Note 2] 4 3.5 to 4mm/day [Note 2] 5 3 to 3.5mm/day [Note 2] 6 2mm/day to 3mm/day [Note 2] 7 2mm/day or less

Notes: 1. Topsoil minimum depth of 250mm, and dripline and emitter spacing of 0.3m x o.3m. 2. The higher loading rates are only applicable where there is at least 50% reserve area. 3 Effective distribution in lawns is best achieved using closely spaced lines and emitters (0.3m x 0.3m) and use of very conservative loading rates of less than 3mm/day. 4. The land disposal area and/or linear length of irrigation lines are to be adjusted when the line spacing is varied from 1.0m [Ref 17].

138 Section 9.3.1 [p.

150/151]

9.3.1 General This whole subsection has been amended and carried back into 9.1.3 (see Item 132

above)

Recommendations: (a) Delete existing 9.3.1 General.

(b) Change numbering of 9.3.2 through to 9.3.4 to 9.3.1 through to 9.3.3.

139 Section 9.3.2 [p.

151]

9.3.2 LPP Function and Application The LPP system was developed in the US for use in either ----- perforated plastic pipe laterals (Figure 9.2).

The distinction between LPP as an irrigation method, and LPP as a dose loading

method for soakage systems needs to be delineated carefully through the document.

This has already been done in the recommended changes to 8.6.3 (see Item 125

above), and should be further emphasised here. (Note also revised Section

numbering from Item 138 above.) Note also that Figure 9.2 does not illustrate LPP

irrigation, but LPED (albeit incorrectly), and thus the referral should be dropped

from the end of the second sentence. Section numbering changes (see Item 138

above).

Recommendation: Change text to: 9.3.1 LPP Function and Application The LPP system septic tank effluent subsurface irrigation system was developed in the US for use in either ----- perforated plastic pipe laterals.

140 Section 9.3.2 [p.

151]

It is essential that LPP and LPED systems are dose loaded either by siphon or pump to ensure even distribution along the entire length of each line and utilisation of the entire infiltration surface.

This is fairly self evident. But the terminology has been borrowed from LPP/LPED

distribution material in Section 8.6. We need to customise it better here.

Recommendation: Change text to: It is essential that LPP irrigation systems (as for LPED) are dose loaded either by siphon or pump to ensure even distribution along the entire length of each trench lateral and thus ensure effective “areal” coverage of the design area.

TP58 3rd


30


141 Section 9.3.3 [p.

152]

9.3.3 Advantages and Disadvantages Disadvantages

Effective soakage beyond the immediate locality of pipe work -----between LPED lines frequently ineffective, providing;

Less even distribution than that provided by properly installed drip irrigation systems or LPED systems;

The Section numbering changes. The reference to LPED should read LPP. The word

“providing” is not needed. Emphasise LPED irrigation.

Recommendation: Change text to: 9.3.2 Advantages and Disadvantages

It is essential that LPP irrigation systems (as for LPED) are dose loaded either by siphon or pump to ensure even distribution along the entire length of each trench lateral and thus ensure effective “areal” coverage of the design area.

142 Section 9.3.3 [p.

152]

Will not operate effectively in Category 5 and 6 soils without adequate topsoil cover.

The impression given here could be that the adequate topsoil cover is to be over the

top of the LPP irrigation lines.


Will not operate effectively in Category 5 and 6 soils without adequate topsoil depth.

143 Section 9.3.4 [p.

152]

9.3.4 Design and Operation Recommended “areal” loading rates for design sizing of LPP are as follows.

The emphasis in earlier changes is to indicate that LPP (like LPED) is an irrigation

system for septic tank (primary) effluent). Here a design loading concession is given

for secondary effluent. Some explanatory text needs to be added.

Recommendation: Add text as follows: 9.3.3 Design and Operation Design sizing of LPP systems has traditionally been based on subsurface irrigation of primary treated effluent (usually from septic tanks).Where LPP is used for subsurface irrigation of secondary effluent, then a concession in design loading rate can be made as below. Recommended “areal” loading rates for design sizing of LPP are as follows.

144 Section 9.3.4 [p.

152]

System layout has been based on 1500mm spacing between trench centrelines, with the “areal” ---- effectiveness of the area between LPED lines for ET assist ------- design areal loading rate is based on a maximum area of 1m per linear metre of line.

What is essentially being said here is that the preferred trench spacing is 1.0m

instead of 1500mm. So why not offer the option of going for 1.0m spacing?

Recommendation: Add (and amend) text as follows: System layout has been based on 1500mm spacing between trench centrelines, with the “areal” ---- effectiveness of the area between LPP lines for ET assist ------- design areal loading rate is based on a maximum area of 1.0m per linear metre of line. Where construction methods allow, then the trench spacing may be reduced to 1.0m in order to obtain full use of the soil between trenches.

TP58 3rd


31


145 Section 9.4.1 [p.

152/153]

9.4.1 Function and Application LPED as a distribution method for trench land disposal is discussed in detail in Section 8.6 above. Again LPED lines comprise a perforated dose line installed within agricultural drainage coil. The system involves low pressure pump dosing of predominantly improved septic tank effluent (large septic tank with outlet filter). LPED graveless trenches are an alternative distribution technique to LPP. They work by flooding inverted nested laterals within a draincoil line from widely spaced perforations in the dose line, avoiding the spot loading effect of LPP, and allow for more effective lineal distribution of effluent along the length of the trench during each dosing operation. It has application for subsurface ”areal” loading irrigation in the following circumstances:

As an alternative to LPP distribution for all the applications as out in Section 9.3 above;

For wastewater distribution in a land disposal system within Category 1 & 2 and 3 soils.

While LPED is superior to LPP distribution, its longterm popularity will depend on how competitive the distribution methodology remains with secondary treatment and associated drip irrigation technology.

This introduction to LPED irrigation repeats a lot of material associated with

Section 8.6 earlier in explaining the difference between LPP and LPED dosing,

without focusing on LPED irrigation. It also refers to “improved septic tank

effluent” when in other places the term “advanced primary treatment” is used (see

Items 97 and 114). Furthermore, it introduces a significant and flawed technical

measure in that it adopts “graveless” trenches completely contrary to the media

trenches used in LPP irrigation (see Item 151 below). This whole introductory piece

needs clarification and correction.

Recommendation: Change and replace text with the following: LPED subsurface irrigation is identical in design sizing, layout and operation as LPP (Section 9.3 above), except that LPED dosing lines are laid within the shallow narrow media filled trenches instead of LPP dosing lines. Details of LPP and LPED dosing configurations are covered in Section 8.6 above. It will be recalled that LPED utilises a perforated dose line nested within draincoil to enable more effective distribution of effluent along the full length of the distribution trench, thus avoiding the spot loading associated with LPP. While LPED is superior to LPP distribution, its longterm popularity will depend on how competitive the distribution methodology and cost remains compared to secondary treatment and associated drip irrigation technology. Note that, as for LPP irrigation, there is a design loading rate concession for secondary effluent in LPED irrigation systems.

146 Section 9.4.2 [p.

153]

9.4.2 Design and Operation for General Purposes This whole Section should be integrated with the revisions proposed for Section

9.4.5 below (see Item 151 below )

Recommendation: Delete Section 9.4.2, and renumber subsequent Sections.

147 Section 9.4.3 [p.

153]

9.4.3 Advantages and Disadvantages LPED systems have the following advantages and disadvantages over LPP for land disposal of wastewater:

This is not correct – the advantages/disadvantages are not related to direct

comparison with LPP – they stand on their own as indeed the LPP ones do in

Section 9.3.3 (now 9.3.2).

Recommendation: Change text to: 9.4.2 Advantages and Disadvantages LPED subsurface irrigation systems have the following advantages and disadvantages:

148 Section 9.4.3 [p.

154]

Disadvantages

Effective soakage beyond the immediate locality of pipe work difficult to predict at the design stage: Wastewater is not evenly distributed throughout the entire disposal field, with areas between LPED lines frequently ineffective, providing;

Editing needed here to parallel the material in the LPP section.

Recommendation: Change text to: Disadvantages

Effective soakage beyond the immediate locality of pipe work difficult to predict at the design stage: wastewater is not evenly distributed throughout the entire disposal field design evapotranspiration area, with areas between LPED lines frequently ineffective;

149 Section 9.4.4 [p.

154]

9.4.4 Design and Operation for Free Draining Soils This Section is not relevant in the context of LPED irrigation, as it is referring back

to the use of LPED dose loading. This cross referral is adequately dealt with

elsewhere. Hence it can be deleted.

Recommendation: Delete Section 9.4.4 and renumber subsequent Sections.

TP58 3rd


32


150 Section 9.4.5 [p.

154]

9.4.5 LPED Design and Operation for Slowly Draining Soils This title can be amended to deal with generic design and operation. There is no

need to contrast the title with 9.4.4 above, as it has to go. Hence amend to be

consistent with the LPP Section 9.3.4.

Recommendation: Change title (allowing for re-numbering of Sections) to: 9.4.3 Design and Operation

151 Section 9.4.5 [p.

154]

Shallow and narrow LPED trenches are suitable for sites with a good topsoil layer having suitable texture and structure and at least 250mm deep and overlying Category 5 to 6 soils. LPED comprises a series ---- or slotted pressure pipe (Figure 9.2). The LPED trench base ----- there is no breakout from low points. Trenches are backfilled with topsoil, which should be mounded over the trench to allow for settlement. Concrete blocks located -----.

The wording here lacks clarity, and needs to address the role of LPED irrigation in

all soils categories. The use of topsoil backfill is totally inappropriate (as it is for

LPP) and indeed the wording of the “advantages” and “disadvantages” retains the

implication that the LPED dose lines are laid in aggregate.

[Note: It should be noted that Innoflow at one stage specified topsoil backfill for

LPED based on advice they presumably received from the US. However, one such

system installed to their specification failed in South Auckland, following which I

advised them to revert to the normal LPED installation using media filled shallow

narrow trenches. There is no way that we can risk using soil to surround the

draincoil and thus block the slots when bacterial slimes develop in and across those

slots. With topsoil surround, the advantages listed for media filled trenches then

disappear, and the potential for failure becomes very high. All LPED irrigation

systems to date should have been in accordance with the 1994 edition of TP58, that

is using media filled trenches. So, where is the experience in operating topsoil filled

trenches that give rise to it being incorporated in this 3rd

edition?]

Recommendation: Change text as follows (carrying over the content from the

deleted 9.4.2 as per Item 146 above): The design and operational requirements for LPED subsurface irrigation systems are in general the same as those for LPP (Section 9.3.3). The irrigation system is suitable for Category 3 to 6 soils with good structure and texture and adequate topsoil depth. Topsoil should be between 150mm depth (soil Categories 3 & 4) and 250mm depth (soil Categories 5 & 6). LPED comprises a series ---- or slotted pressure pipe surrounded by distribution media (Figure 9.2). The LPED trench base ----- there is no breakout from low points. The trench media (aggregate) is carried to ground surface level, and topsoil mounded over the trench. Concrete blocks located -----.

152 Section 9.4.5 [p.

154]

Site requirements are:

Minimum topsoil depth 250mm;

Maximum ground slope of 15º.

We now need to amend these to fit the changes in Item 151 above.

Recommendation: Change text to: Site requirements are:

Minimum topsoil depth for soil Categories 3 and 4, 150mm;

Minimum topsoil depth for soil Categories 5 and 6, 250mm; and

Maximum ground slope of 15º.

153 Figure 9.2 [p. 155] Figure 9.2: Typical Subsurface LPED Land Disposal System This title is incorrect. It should reflect the content of the Section.

Recommendation: Change title to: Figure 9.2: LPED Subsurface Irrigation System – Typical Details

TP58 3rd


33


154 Figure 9.2 [p. 155] [The diagram structure and labelling.] There are several changes needed to enable the diagram to fit the recommended

changes to the text.

Recommendation: Changes are proposed as follows:

Current text Proposed text

Where shown on trench: 250mm depth

Replace with: 200 mm

Minimum 250mm topsoil depth Minimum 250mm topsoil depth for Soil Categories 5 & 6

Allow extra topsoil over trench for settlement Topsoil mounded over drainage fabric (filter cloth) placed on trench media at ground surface.

Where topsoil shown filling both

trench cross sections and as fill in the

trench long section

Replace with:

Distribution media (aggregate)

LPED lines to be spaced at 1500mm centres LPED lines to be spaced at 1.0 to 1.5 m centres

Effective length of Disposal Trench Effective length of Irrigation Trench

From pumped distribution manifold. To include orifice -----.

From pumped distribution manifold or automatic sequencing valve. Where manifold used, to include orifice ----.

Add “Filter cloth” at ground level over

media and label it.

155 Section 9.4.5 [p.

156]

Recommended “areal” loading rates for design sizing of LPED are as follows:

Primary or secondary treated effluent on flat to moderate slopes with a minimum of 250mm of good topsoil: 3mm to 5mm/day.

Effective irrigation area for areal loading is 1m.

If a concession is given for secondary effluent into LPP irrigation, then given that

LPED irrigation is a more effective system, why not the same concession here? (See

Item 143 above.)

Recommendation: Change text as follows: Design sizing of LPED irrigation systems has traditionally been based on subsurface irrigation of primary treated effluent (usually from septic tanks). Where LPED is used for subsurface irrigation of secondary effluent, then a concession in design loading rate can be made as below. Recommended “areal” loading rates for design sizing of LPED irrigation are as follows. Primary effluent on flat to moderate slopes and Category 3 and 4 soils with a minimum of

150 mm at 3mm/day or a minimum of 250mm of good topsoil at 5mm/day.

Primary effluent on flat to moderate slopes and Category 5 and 6 soils with a minimum of 250mm of good topsoil at 3mm/day.

Secondary effluent on flat to moderate slopes and Category 3 and 6 soils with a minimum of 150mm to 250mm of good topsoil at 5mm/day.

TP58 3rd


34


156 Section 9.4.5 [p.

156]

With trench spacing around 1500mm the concept is to wet ----- only be applied to a maximum distance of 1.0m from the trench. LPED trenches are an acceptable land disposal method in suitable soil and slope conditions. Pumped or siphon dosing is essential to ensure uniform spread of effluent along the trench length, and during construction, test dosing with clean water should be undertaken prior to filling over the pressure distribution lines to ensure that the system will perform as designed.

As for LPP irrigation, we can modify the text right through here to provide clarity.

Once again LPED trenches are referred to a synonymous with LPED subsurface

irrigation. We also can bring more of the deleted 9.4.2 in here.

Recommendation: Change text as follows: With trench spacing around 1500mm the concept is to wet ----- only be applied to a maximum distance of 1.0m from the trench. Where construction methods allow, then the trench spacing may be reduced to 1.0m in order to obtain full use of the soil between trenches. LPED subsurface irrigation is an acceptable land disposal method in suitable soil and slope conditions. Pumped or siphon dosing is essential to ensure uniform spread of effluent along the trench length. Automatic sequencing valves enable a single dose per day to be flood loaded and allowed to drain with 24 hours of in-soil treatment prior to the next dose. The dose volume should be controlled to ensure that the applied effluent in an individual trench on each loading cycle does not flood the media (aggregate) to a depth of more than 50mm to 75mm. During construction, test dosing with clean water should be undertaken prior to completing placement of the media around the LPED lines and covering over the completed media at ground level with drainage fabric (filter cloth) over which is mounded topsoil. The commissioning test is necessary to ensure the system is evenly loaded and will perform as designed.

157 Sections 9.5.1 and

9.5.2 [p. 157] plus

Figure 9.3 [p. 157]

LPED lines, LPED Figure 9.3: Typical Surface LPED Land Disposal System

The terminology in the text need changing to replace “LPED lines” or “LPED” with

“LPED trickle irrigation lines” .The Figure title then needs correcting to reflect the

change in text.

Recommendations: (a) Change throughout the two sections “LPED lines” and “LPED” to: LPED trickle irrigation lines

(b)Change title as follows: Figure 9.3: LPED Surface Trickle Irrigation System – Typical Details

158 Figure 9.3 [p. 157] [The diagram labelling.] There are several changes needed to enable the diagram to fit the text.

Recommendation: Changes proposed are as follows:

Current text Proposed text Cover soil to be held in place by durable plastic ---- and downslope sides.

Cover material to be held in place by durable plastic ---- and downslope sides.

L.P.E.D (Low Pressure Effluent Distribution) lines placed on the ----- compost or equivalent.

LPED (low pressure effluent distribution) trickle irrigation lines placed on the ----- compost or equivalent.

L.P.E.D comprises a 30mmØ perforated pumped ---- slotted drain coil line, and covered with topsoil.

LPED dose lines comprise a 30mmØ perforated pumped ---- slotted drain coil line. When laid on the ground as for trickle irrigation, the lines are covered with appropriate material as indicated above.

TP58 3rd


35


159 Section 9.6 [p. 157] 9.6 Spray Irrigation The inclusion of spray irrigation systems within AS/NZS 1547 ---- to the use of ATP and spray irrigation ----.

Where is ATP used in the text elsewhere?

Recommendation: Change text to: The inclusion of spray irrigation systems within AS/NZS 1547 ---- to the use of AWTS secondary treatment and spray irrigation ----.

160 Section 9.6 [p. 157] Other considerations are; aerosol formation and drift, separation distances from property boundaries and public access to the irrigation area including with holding times.

Clarity required here.

Recommendation: Change text to: Other considerations are: wet weather storage; control of irrigation during rainfall; aerosol formation and drift; separation distances from property boundaries; and public access to the irrigation area.

161 Section 10. [p. 158] Following are the disposal methods covered in this section in the order below.

Conventional Trenches;

Shallow and Narrow Trench Systems;

Discharge Control Trench Systems;

Deep Trench Systems;

Infiltration Systems;

Deep Bores;

Conventional Beds;

Evapotranspiration Beds;

Mound Land Disposal Systems; and

Bottomless Sand Filters.

In fact the systems are not covered in the order below.

Recommendation: Reorder and expand the list of systems to the following: Following are the disposal methods covered in this section in the order below.

Conventional Trenches;

Shallow and Narrow Trench Systems;

Discharge Control Trench Systems;

Deep Trench Systems;

Conventional Beds;

Discharge Control Beds;

Evapotranspiration Seepage Beds;

Wisconsin Mound Land Disposal Systems;

At-grade Fill Mound Systems;

Bottomless Sand Filters.

Infiltration Systems; and

Deep Bores;

162 Section 10.1 [p. 158] 10.1 TRENCHES The first paragraph of this section repeats in large measure material already

presented under the heading of “”subsoil soakage – general” in 9.1, page 144 (see

Item 132 above). This has been one of the features of this edition of TP58 – its very

wordiness, with a lack of editing attention to ensure integrated packaging of

information. The repetition here clearly comes about as a result of restructuring a

July 2003 draft in rewriting for the August 2003 issue of a formal draft for

consultation.

Recommendation: No action proposed; let the repetition stand. However, carryout

a full professional edit during revision (see Item 86 above).

163 Section 10.1 [p. 158] The higher loading rates set out in AS/NZS 1547:2000 for soakage systems to which secondary effluent is applied are discussed in Section 10.2.1. Increased secondary loading rates are not covered here in TP58 and are not a permitted activity in the Auckland Region.

This statement is confusing, as in fact secondary loading rates are “covered here in

TP58” in Section 10.2.1 as herein stated!

Recommendation: Change text to: The higher loading rates set out in AS/NZS 1547:2000 for soakage systems to which secondary effluent is applied are discussed in Section 10.2.1. Increased secondary loading rates are not a permitted activity in the Auckland Region.

TP58 3rd


36


164

Section 10.1.3 [p.

160]

10.1.3 Shallow and Narrow Trench Systems This sidewall contact is enhanced by decreased widths (200 to 300mm), thus enabling design loading at “least conservative” higher rates where secondary effluent is applied (refer Section 10.2).

This restriction to “secondary effluent” here is contradictory to the “least

conservative” guidelines in 10.1.1 which are directly elated to primary treated

effluent.

Recommendation: Change text to: This sidewall contact is enhanced by decreased widths (200 to 300mm), thus enabling design loading at “least conservative” higher rates (refer Section 10.2).

165 Section 10.1.3 [p.

160]

Trenches are typically installed at 2.0m centres to allow sufficient space for construction of replacement trenches in the event of installed trenches failing.

This provision means that the reserve area and the initial installed area are the same

portion of the lot, one overlaying the other. Hence, where trenches are spaced at

2.0m or greater, the 100% reserve area requirement for shallow trenches (Table 5.3,

page 46) can be waived. [See Item 23 above]

166 Section 10.1.4 [p.

161]

10.1.4 Discharge Control Trench System General Rapidly draining Category 1 gravels and coarse sands provide -----. Into the Category 1 soil a discharge control ----- into Category 1 soils and there are groundwater protection concerns.

In Table 10.2, page 165, discharge control trenches are required for both Category 1

and 2 soils. Hence amend here.

Recommendation: Add text as follows: Rapidly and freely draining Category 1 and 2 gravels and coarse sands provide -----. Into the Category 1 and 2 soil a discharge control ----- into Category 1 and 2 soils and there are groundwater protection concerns.

167 Section 10.1.4 [p.

161]

10.1.4 Discharge Control Trench System General

The “discharge control trench” system described here makes no cross reference to

“discharge control bed system” for which design loading rate (DLR) discussion is

outlined on page 162. There is also need for a crosslink to “bottomless sand filters”

and discharge control beds in Section 10.5 (new 10.6) on page 178 (see Item 244

below).

Recommendation: Add a third paragraph under a new sub-heading after “----

Figure 10.2 shows a typical discharge control trench.” as follows: Discharge Control Bed System Where site conditions are restrictive to the provision of a discharge control trench system, then a discharge control bed may be used. The bed details should be as shown for trenches in Figure 10.2, with the LPED dosing lines centred at 600mm centres. It should be noted that although such a discharge control bed system appears to have the configuration of a bottomless sand filter, design and installation details are different for the two systems (see Section 10.6).

168 Figure 10.2 [p. 161] Figure 10.2 Schematic of a Typical Discharge Control Trench Three details require attention here. The first is that we should emphasise that LPED

is the best dosing arrangement (as per text for “wastewater distribution”, page 162).

The second is that the sand media fill should be better specified. The third relates to

the source of the diagram, which is now amended from the original AS/NZS 1547

diagram.

Recommendations: (a) Change “perforated distribution pipe” to “LPED dose line”

(b) Add to sand fill media “Uniformity coefficient < 4.0”

(c) Change Source to “Based on AS/NZS 1547:2000”.

TP58 3rd


37


169 Section 10.1.4 [p.

162]

Wastewater Distribution Wastewater is to be dose loaded to the LPED distribution system located in the top of the discharge control trench.

This needs amplification relative to the use of beds as per Item 168 above.

Recommendation: Change text as follows: Wastewater effluent is to be dose loaded to LPED lines located in distribution media laid over the sand in the discharge control trench or bed. For discharge control bed systems the LPED lines at 600mm centres across the width of the bed may be designed for dose loading all at once (via manifold), or consecutively in sequence (via automatic sequencing valve).

170 Section 10.1.4 [p.

162]

Design Loading Rate Design loading rates for a Discharge Control Trench and Discharge Control Beds are provided in Tables 10.1, 10.2 and 10.3. The designer ---- draining sand and gravel. Trenches are designed for basal area loading. Primary treated wastewater is to be loaded at the most conservative loading rate of 35mm/day and secondary wastewater loaded at up to a maximum of 50mm/day.

This is not correct. Table 10.1 differs from Tables 10.2 and 10.3. Clarity in

discharge control DLR values should be provided by using only Table 10.1.

Furthermore, the text in this paragraph has different DLR values from those set out

in Table 10.1. The sentence “ Primary treated wastewater is to be loaded at the most

conservative loading rate of 35mm/day and secondary wastewater loaded at up to a

maximum of 50mm/day” can be deleted, as it is quite inconsistent with the Table.

The Table then stands on its own.

Recommendation: Change text to: Design loading rates for Discharge Control Trenches and Discharge Control Beds are provided in Table 10.1. The designer ---- draining sand and gravel. Both trenches and beds are designed for basal area loading. Primary treated wastewater is to be loaded at the most conservative loading rate of 35mm/day and secondary wastewater loaded at up to a maximum of 50mm/day.

171 Table 10.1 [p. 162] Table 10.1 Discharge Control Trench Loading Rates The DLR values for beds will be the same.

Recommendation: Change Title to: Table 10.1 Discharge Control Trench and Bed Loading Rates

172 Section 10.1.4 [p.

162]

Construction Reference has to be made to beds in here as per Item 167 above.

Recommendation: Add a third paragraph after “Construction details are shown in

Figure 10.2” as follows: Construction details for a discharge control bed are to be based upon those for trenches as per Figure 10.2, but modified in accordance with the requirements for distribution as set out under “wastewater distribution” above.

173 Section 10.1.5 [p.

162]

10.1.5 Deep trench Systems Narrow deep trenches may be -----sidewall soakage only. As the sidewalls are unevenly loaded from top to bottom during draining, the most conservative design loading rate is to be used. The design infiltrative surface ----- a worked design example provided in Technical Sheet 3.

Clarity needs to be provided here as to which DLR values are to be used. Secondary

effluent only is allowed to be applied to deep trenches, but the “most conservative”

and “least conservative” DLR s apply to primary effluent. Note that the Technical

Sheet referral is incorrect.

Recommendation: Amend and add new material with actual DLR values; split

paragraph in two; all as follows: Narrow deep trenches may be -----sidewall soakage only. As the sidewalls are unevenly loaded from top to bottom during draining, the most conservative design loading rates as for primary effluent are to be used as follows: Category 2 soils – 25mm/day secondary effluent loading rate to sidewalls. Category 3 soils – 20mm/day secondary effluent loading rate to sidewalls. The design infiltrative surface ----- a worked design example provided in Appendix D, Technical Sheet D2.

TP58 3rd


38


174 Section 10.1.5 [p.

162]

Wastewater Distribution Wastewater is to be dose loaded to an LPED distribution system to ensure even loading of the entire trench length. .

Editing required. What is more important is setting the size of the daily dose.

Recommendation: Amend and add new material as follows: The secondary treated effluent is to be dose loaded via LPED dose lines to ensure even loading of the entire trench length. The dose volume is to comprise the full daily flow applied in a single dose from a holding tank or pump sump. This is to maximise contact with sidewalls. A typical design (refer Technical Sheet D2) indicates a once daily dose can result in up to 50% sidewall contact if a single trench is used. Dividing the trench into two to enable alternating daily dosing of each half via automatic sequencing valve can be used to fill trenches to full sidewall depth at each dose. However, a high level overflow connection between the twin trenches must be provided to ensure that either trench, if overfilled, does not “break out” to ground surface.

175 Figure 10.3 [p. 163] [The diagram labelling.] There are several changes needed to enable the diagram to fit the text.

Recommendation: Changes proposed are as follows:

Current text Proposed text Perforated distribution line

and LPED distribution line nested in perforated pipe

Replace both with: LPED dose line (perforated pressure pipe nested within draincoil)

300 mm min 150mm min – 300mm max

Perforated distribution line (plugged at end with LPED distribution)

Perforated pressure pipe within the LPED line to be plugged at its end.

176 Section 10.2.1 [p.

163]

10.2.1 Effluent Quality and Design Loading Rate Tables 10.2 and 10.3 show a range -----.

This Section 10.2 relates to trenches, and Table 10.3 relates to beds.

Recommendation: Change text to: Table 10.2 shows a range -----.

177 Section 10.2.1 [p.

164]

There are conflicting arguments both ----- surface and within the underlying soil. Where anaerobic conditions develop the anaerobic microorganisms are not able to breakdown the waste material [Ref 3]. Secondary treated ---- with reduced levels of faecal coliforms.

This paragraph has an inaccuracy in the text which seems to be carried in from one

of the references. I cannot believe the reference would have said what is stated about

“anaerobic microorganisms are not able to breakdown waste materials” as clearly

they can (such as in digestion of solids in septic tanks sludge, and assimilation and

breakdown of organic matter via the slimes coating trench base and walls). Hence

amend text while removing the referral to Ref.3.

Recommendation: Change text to: There are conflicting arguments both ----- surface and within the underlying soil. Where anaerobic conditions develop the anaerobic microorganisms are not able to breakdown the waste material as rapidly as aerobic microorganisms under aerobic conditions. Secondary treated ---- with reduced levels of faecal coliforms

178 Section 10.2.1 [p.

164]

The USEPA [Ref 3 and others Refs 18, 19, 20] recommend caution -----.

Editing.

Recommendation: Change text to: The USEPA [Ref 3] and others [Refs 18, 19, 20] recommend caution -----.

TP58 3rd


39


179 Section 10.2.1 [p.

164]

Designers are discouraged from applying elevated loading rates for secondary treated effluent. The application of higher secondary loading rates are not a permitted activity in the Auckland region and will be evaluated on a case by case basis as part of discharge consent application process.

The case for not accepting the increase in DLR values for secondary effluent is well

argued through the material on page 164. There appears to be no recognition of the

fact that higher loading rates can only be used in the context of a full environmental

effects assessment (which would take into account all of the potential constraints

outlined in this section), nor the fact that the DLR values allow for the hydraulic

conductivity capacity of the individual soil categories, nor the fact that the USEPA

manual (2002) [Ref 3] includes recommended DLR values for secondary effluent

[see On-Site NewZ Issue 02/4 October 2002 for a full comparison.] There has been

considerable reliance on Ref. 3 throughout this Edition of TP58, but not on this

matter. Note also the concession already given to LPP and LPED subsurface

irrigation systems where secondary effluent in used in place of primary effluent for

sizing irrigation areas [see Items 143 and 155 above].

Recommendation: Edit and expand o: Although it is recognised that both AS/NZS 1547/2000 [Ref. 1] and the USEPA [Ref. 3] provide a concession on design loading rates by allowing the use of higher values for secondary effluent, designers within the Auckland region are discouraged from applying elevated loading rates for secondary treated effluent. The application of higher secondary loading rates is not a permitted activity under ARC rules. Proposals for use of higher secondary effluent loading rates for trenches in the Auckland region will be evaluated on a case by case basis as part of a discharge consent application process.

180 Table 10.2 [p. 165]

NOT PERMITTED ACTIVITY IN AUCKLAND REGION

mm/day

AS/NZ5 [Note 3]

This heading requires editing:


Secondary Effluent

mm/day [NOT a PERMITTED ACTIVITY in

the AUCKLAND REGION]

Based on AS/NZS values [Note 3]

181 Table 10.2 [p. 165] Notes: 1. The Soil Categories in this ---- of AS/NZS 1547:2000 (refer Table 6.1).

Incorrect reference to Table.

Recommendation: Edit to: 1. The Soil Categories in this ---- of AS/NZS 1547:2000 (refer Table 5.1).

182 Table 10.2 [p. 165] 3. This column represents alterative the trench loading rates based on AS/NZS 1547:2000 rates using soils categories of weakly structured to massive soils correlated to TP58 soil categories. The ARC does not endorse these, as they are not considered appropriate in the Auckland Region.

This is badly worded – doesn’t make sense.

Recommendation: Change text to: 3. This column represents secondary effluent loading rates based on AS/NZS 1547:2000 rates for weakly structured to massive soils, and correlated with TP58 soil categories as per Table 5.1. The ARC does not endorse these, as they are not considered appropriate in the Auckland Region.

TP58 3rd


40


183 Table 10.2 [p. 165] 4. For Category 1 and 2 soils, LPED OR PCDI methods are required to ensure even loading of the design area.

The use of PCDI in these soils has already been discussed above (see Item 134

above). LPED is the most appropriate dosing method. Use of drip line emitters, even

at high hourly discharge rates, means a significant pumping time to discharge the

volumes required to dose a trench. PCDI is not the best distribution method, and

should be abandoned. Note that 10.1.2 on page 160 requires dose loading for

Category 1, 2 and 3 soils.

Recommendation: Change text to: 4. For Category 1, 2, and 3 soils, LPED dose loading is required to ensure even loading of the design area.

184 Table 10.2 [p. 165] 5 Special design considerations are required for Category 1 and 2 soils; refer Section 10.1.4 Discharge Control Trenches. The least conservative loading rates apply only to secondary treated wastewater. 6. The maximum loading rate for any effluent quality into Category 1 and 2 soils is recommended at 50 mm/day.

There are several inconsistencies within these two Notes. The fact of the matter is

that Section 10.1.4 makes it compulsory to use discharge control trenches for

Category 1 and 2 soils, and these notes effectively confirm this. In addition Table

10.1 sets out the DLR values for Discharge Control Trenches, which are different to

here (see Item 170 above). It would seem that the best approach is to allow

conventional trenches for only Category 3, 4 and 5 soils, and adjust Table 10.2 and

the Notes accordingly. Details of this adjustment are set out below:

Recommendation: Revise Notes 5 and 6 in deference to changes made below in

Item 185.

185 Table 10.2 [p. 165] 1 [Note 4]

Gravel, coarse sand – rapid draining [Note 4]

35 [Note 5]

50 [Note 5]

50

2 [Note 4]

Coarse to medium sand – free draining [Note 7]

25 [Note 5]

35 [Note 5]

50

On the basis of Item 184 above, reorganise this table to confirm discharge control

trenches only trench (or bed) system to be used for soil Categories 1 and 2.

Recommendation: Change table to:

1 [Note 4]

Gravel, coarse sand – rapid draining

Conventional trenches not

suitable [Note 5]


suitable [Note 5]

50

2 [Note 4]

Coarse to medium sand – free draining


suitable [Note 5]


suitable [Note 5]

50

186 Table 10.2 [p. 165] [New Note 5] Recommendation: Substitute new Note 5: 5 Conventional trenches are not suitable for Category 1 and 2 soils. Use Discharge Control Trenches or Beds (Section 10.1.4).

TP58 3rd


41


187 Table 10.2 [p. 165] 3

Medium fine and loamy sand – good drainage

20

30 30 to 50

Note 7 regarding windblown sand now rightly belongs in here (but change

numbering to 6). Add in Note 4 (see Item 183 above) in first column.

Recommendation: Change table as below, and number old Note 7 as Note 6.

3 [Note 4]

Medium fine and loamy sand – good drainage [Note 6]

20

30 30 to 50

188 Table 10.2 [p. 165] [Notes 8 and 9] 8. Trenches should only be considered in Category 5 soils where more appropriate shallow disposal options such as drip irrigation or LPED cannot be used.

These become Notes 7 and 8. Distinguish between LPED dosing and LPED

irrigation (see Item 156 above)

Recommendations: (a) Change text of Note 8: 8. Trenches should only be considered in Category 5 soils when more appropriate shallow disposal options such as drip irrigation or LPED subsurface irrigation cannot be used. (b) Renumber Notes, 8 to 7, and 9 to 8.

189 Section 10.3 [p. 166] 10.3 BED LAND DISPOSAL SYSTEMS The section numbering runs consecutively through “conventional beds” into “ETS

beds” without distinction, when in fact they are two different systems. Hence we

need to split up into two topic areas.

Recommendation: Split conventional and ETS bed systems into two subsections as

follows (then renumber subsequent sections from 10.4 Mounds on).: 10.3 BED DISPOSAL SYSTEMS – CONVENTIONAL BEDS 10.3.1 Function and Application 10.3.2 Construction details 10.4 BED DISPOSAL SYSTEMS – EVAPO-TRANSPIRATION SEEPAGE (ETS) BEDS 10.4.1 Function and Application 10.4.2 Water Balance 10.4.3 Design Notes and Specifications 10.4.4 Design Sizing 10.4.5 Bed Construction Details

TP58 3rd


42


190 Section 10.3.1 [p.

166]

10.3.1 Conventional Beds Conventional bed systems are a second best alternative to trenches ----- in relatively good draining Category 1 to 4 soils. Table 10.3 sets out ---- bed bottom area and Tables TS5-1 and TS5-2. Where the bottom width ----- as a conventional bed for design purposes. The design should be modified for discharge of wastewater into Category 1 soils to a discharge control bed.

Given the last sentence, and all the related changes made for trenches in Category 1

and 2 soils, we need to alter this paragraph and then embark on a series of

consequential changes in Table 10.3. Note that the reference to TS5-1 and TS5-2 are

quite out of context here. To follow up on discharge control beds, we need to make

reference here to the earlier sections dealing with these under “discharge control

trenches and beds” (see Items 169 to 172 above}.

Recommendation: Change heading and text as follows: 10.3.1 Function and Application Conventional bed systems are a second best alternative to trenches ----- in relatively good draining Category 3 and 4 soils. Discharge Control Beds should be used for Category 1 and 2 soils, except where there are specific environmental concerns regarding bacteria and viruses. In such situation a bottomless sand filter should replace the discharge control trench (Section 10.6). Table 10.3 sets out ---- bed bottom area. Where the bottom width ----- as a conventional bed for design purposes. Design modifications and loading rates for discharge control beds are discussed above in Section 10.1.4.

191 Section 10.3.2 [p.

166]

10.3.2 Construction Details

It is recommended that beds be maintained at least 1.5m edge to edge.

The maximum bed width 1.0m to 4.0m

Multiple distribution lines will be required for beds more than 1.5m width.

Minimum separation width 1.0m. Refer also to 10.3.4 for design requirements.

These construction details are most unhelpful as they are contradictory and

incomplete. The reference to “10.3.4 for design requirements” does not make sense.

Statements in 10.3.3 regarding “maximising evapo-transpiration” for conventional

beds need to be stated here, not left in 10.3.3 (see Item 204 below).

Recommendation: Change text as follows: 10.3.2 Construction Details

Recommended minimum bed width is 1.0m, maximum width 4.0m.

Spacing between adjacent beds to be a minimum of 1.0m (recommended normal spacing 1.5m).

Recommended effluent distribution method is flood loading via pump or siphon to distribution box, or dose loading via LPED.

Distribution/dose lines to be no greater than 1.5m spacing (multiple distribution lines required for bed width greater than 1.5m).

The area between and around the outer edges of the beds should be planted with suitable plants (refer Appendix G) to maximise evapo transpiration (ET) assist in managing sideways infiltration of moisture from the edges of the bed into the surrounding soil (see Section 10.4.1).

192 Section 10.3.2 [p.

166]

Bed Design Example

This example seems totally out of place here. No other examples are provided in

Chapter 10 – they are all located in Appendix D Technical Sheets.

Recommendation: Relocate this Bed Design Example to Appendix D.

TP58 3rd


43


193 Table 10.3 [p. 167]

Primary Effluent

MM/DAY [NOTE 2]

This Table requires editing as per Table 10.2 (see Items 180 to 188 above).



Primary Effluent

mm/day [Note 2]

194 Table 10.3 [p. 167]

NOT PERMITTED ACTIVITY IN AUCKLAND REGION

Secondary Effluent

mm/day [Note 2]


Recommendation: Restructure and change text to:

Secondary Effluent

mm/day [NOT a PERMITTED ACTIVITY in

the AUCKLAND REGION]

Based on AS/NZS values [Note 3]

195 Table 10.3 [p. 167] Notes: 1. The Soil Categories in this ---- of AS/NZS 1547:2000 (refer Table 6.1).

Incorrect reference to Table.

Recommendation: Edit to: 1. The Soil Categories in this ---- of AS/NZS 1547:2000 (refer Table 5.1).

196 Table 10.3 [p. 167] [Missing Note 3] Note 3 as in Table 10.2 has been omitted here, but should be included.

Recommendation: Add new Note 3 and renumber subsequent Notes. 3. . This column represents secondary effluent loading rates based on AS/NZS 1547:2000 rates for weakly structured to massive soils, and correlated with TP58 soil categories as per Table 5.1. The ARC does not endorse these, as they are not considered appropriate in the Auckland Region.

197 Table 10.3 [p. 167] 3 For Category 1 and 2 soils, LPED methods are required to ensure even loading of the design area. Where groundwater protection from bacterial contamination is important, then a bottomless sand filter may be used (refer Section 10.7 above) The maximum loading rate for any effluent quality inot Category 1 and 2 soils is recommended at 40mm/day. 4. Special design considerations are required for Category 1 and 2 soils; refer Section 10.1.4 Discharge Control Trenches. The least conservative loading rates apply only to secondary treated wastewater.

There are several inconsistencies in these two notes which now need to be changed

to reflect the recommended text revisions in 10.3.1 above (see Item 190).

Recommendation: Change text of Note 3 and renumber to become new Note 4 as

below, and delete original Note 4. Reference to Section 10.7 becomes 10.6 under

new numbering for Chapter 10 sections (see Item 189 above): 4. Discharge Control Beds should be used for Category 1 and 2 soils, except where there are specific environmental concerns regarding bacteria and viruses. In such situations a bottomless sand filter should replace the discharge control trench (Section 10.6).

TP58 3rd


44


198 Table 10.3 [p. 167] 1 [Note 3]


30 [Note 4]

40 [Note 4]

50

2 [Note 3]


20 [Note 4]

30 [Note 4]

50

On the same basis as Item 185 above, reorganise this table to confirm discharge

control beds for soil Categories 1 and 2.

Recommendation: Change table to:

1


Conventional beds not suitable [Note 4]


50

2




50

199 Table 10.4 [p. 168] Table 10.4: Summary of Land Disposal System and Recommended Loading Rates vs. Soil Category

This Table just suddenly appears out of nowhere. Reference has already been made

to it relative to Figure 5.2 on page 42 (see Item 16 above). It should be amended to

make it consistent with a revised Table 5.2 as well as Tables TS5-1 and TS5-2 in

Appendix D. It should also be relocated and provided with explanatory text to a new

Section 10.9 Land Disposal – Summary of Systems (see Item 253 below). Its title

is misleading, as it does not give recommended loading rates (these are set out in the

Appendix D versions of TS5-1 and TS5-2).

Recommendation: Relocate Table to new Section 10.9, and change Title to: Table 10.4: Summary of Land Disposal Systems

200 Table 10.4 [p. 168] [Full Table] The recommended revisions are set out in a new Table 10.4 on page 45 below.

201 Section 10.3.3

[p.169]

10.3.3 ETS [Evapotranspiration Seepage] Beds Refer Item 189 above re renumbering this section.

Recommendation: Renumber and introduce heading for first three paragraphs. 10.4 BED DISPOSAL SYSTEMS - EVAPOTRANSPIRATION SEEPAGE [ETS] BEDS 10.4.1 Function and Application

202 Section 10.3.3

[p.169]

Evapo-transpiration seepage (ETS) systems utilise ---- to achieve disposal [Ref 23]. The applied -----.

Ref 23 doesn’t look right in respect of this citation. Is it Ref. 22? If not, delete

altogether?

Recommendation: Review Reference source or delete.

TP58 3rd


45

Table 10.4: Summary of Land Disposal Systems Land Disposal Method Soil Category

1 Gravel, Course Sand

Rapid Draining

2 Course to Medium

Sand

Free Draining

3 Medium Fine and

Loamy Sand Good Drainage

[Note 1]

4 Sandy Loam and Silt

Loam

Moderate Drainage

5 Sandy Clay Loam,

Clay Loam Moderate to Slow

Drainage

6 Non-swelling Clay

and Silty Clay Slowly Draining

7 Swelling Clay

Poorly or Non Draining

Pressure compensating drip irrigation (PCDI)

[Note 2] [Note 2] [Note 3]

Low pressure pipe (LPP) subsurface irrigation

[Note 4] [Note 4] [Note 5] [Note 5]

Low pressure effluent distribution (LPED) subsurface irrigation


LPED surface trickle irrigation


Conventional trenches

Shallow and narrow trenches

Discharge control trenches

Deep trenches

[Note 6] [Note 6]

Conventional beds

Discharge control beds

Evapo-transpiration seepage beds (ETS)

Wisconsin mounds

At-grade fill mounds

Bottomless sand filters

Infiltration systems

[Note 6 & 7] [Note 6 & 7]

Deep bores

[Note 8]

Notes: 1. Fine wind blown sands can exhibit characteristics similar to Category 5 and 6 soils – caution required when designing in such soil conditions. 2. Emitter and drip line spacing to be reduced to 300mm by 300mm. 3. Special design precautions required in these soil conditions. 4. Minimum topsoil depth 150mm. 5. Minimum topsoil depth 250mm. 6. No environmental or site constraints present. 7. Wastewater effluent quality to be a minimum of secondary treated. 8. High risk method – only to be used in special circumstances.

TP58 3rd


46


203 Section 10.3.3

[p.169]

Evapo-transpiration seepage (ETS) systems utilise ---- to achieve disposal [Ref 23]. The applied ----- nutrients to stimulate plant growth and ET. During periods of wet weather when soil adjacent to the beds become saturated the beds fill with seepage water that can displace effluent and result in surface breakout.

This last sentence is quite misleading and misrepresents actual conditions that occur.

The fact is that the effluent water table in the bed is in equilibrium with the soil

moisture in the surround soils in the space between beds. As rainfall infiltrates into

the natural soil and into the bed topsoil and sand, the effluent which enters at depth

displaces rainwater soil moisture, not the other way around as indicated in the text.

The effect of rainfall on an ETS bed is no different than for a conventional bed or

trench. Breakout does not occur under normal operational conditions under rainfall

influence for any systems operating within their design parameters. Breakout is a

characteristic of overloaded systems which are stressed under both dry and wet

weather conditions.

Recommendation: Change sentence as follows: Evapo-transpiration seepage (ETS) systems utilise ---- to achieve disposal]. The applied ----- nutrients to stimulate plant growth and ET. During periods of wet weather, surface flows are diverted around the edges of the beds (Figure 10.4). Incident rainfall that infiltrates into surrounding topsoil and into the bed itself sits around and above the effluent input. During winter low transpiration rates the effluent water table in the bed rises to take up storage within the media, and sidewall infiltration enables effluent to enter topsoil within the soils between beds.

204 Section 10.3.3

[p.169]

In the past, conventional beds were designed for basal seepage only. The benefits of maximising evapo-transpiration are now recognised in all bed systems by designing to provide for evapo-transpiration and seepage rather than only soakage in conventional beds. Good planting of ETS beds and maintenance of vegetation is critical to achieve the hydraulic absorption required, particularly in Category 5 and 6 soils, where bed disposal methods are otherwise unsuitable.

This paragraph deals with ET assist for all bed systems. We need to transfer advice

related to conventional beds back into 10.3.2. This has been done above (see Item

191). However, conventional beds are not “designed” for ET and seepage, they are

“constructed” this way as explained in the additional paragraph now provided in

10.3.2.

Recommendation: Change text as follows: Conventional beds are designed for basal seepage only, but the benefits of maximising evapo-transpiration to provide ET assist in managing effluent moisture levels in surround topsoil is now recognised as important for all bed systems (see 10.3.2 above). Good planting of ETS beds and maintenance of vegetation is critical to achieve the hydraulic absorption required, particularly in Category 5 and 6 soils, where conventional bed disposal methods are otherwise unsuitable.

205 Section 10.3.4

[p.169]

10.3.4 Function and Water Balance This now changes in accordance with Item 189 above.

Recommendation: Change title as follows: 10.4.2 Water Balance

206 Section 10.3.4

[p.169]

The ETS loading rate of 5mm to 12mm incorporates an allowance for subsoil seepage together with the effects of pan evaporation plus a multiplier to allow for seasonal transpiration from selected vegetation (Table 10.5)

This sentence lacks clarity.

Recommendation: Change text as follows: The ETS loading rate of 5mm/day to 12mm/day (Table 10.5) incorporates an allowance for subsoil seepage together with the effects of pan evaporation plus a multiplier to allow for seasonal transpiration from selected vegetation (Appendix G).

207 Section 10.3.4

[p.169]

This expands the area available for ET assist under the lower winter ET rates.

Expansion of this sentence is helpful.

Recommendation: Change text as follows: This expands the area available for ET assist under the lower winter ET rates, and although the soil becomes wet and possibly spongy, the between bed plantings will accommodate the moisture from the effluent input in proportion to its availability.

TP58 3rd


47


208 Section 10.3.6

[p.169]

10.3.5 Design Notes and Specifications Recommendation: Change title numbering as follows: 10.4.3 Design Notes and Specifications

209 Section 10.3.6

[p.169]

10.3.6 Design Sizing Recommendation: Change title numbering as follows: 10.4.4 Design Sizing

210 Table 10.5 [p.170] Table 10.5: ETS/ASB Design Loading Rates ASB (aerobic seepage bed) systems should be withdrawn, as they were only

introduced for TP58 2nd

Edition after some councils balked at use of ETS beds in

high rainfall areas saying they would not work. When the same ETS designs were

re-presented with the label of ASB, these councils accepted them. This artifice is no

longer needed. (See also Item 22 above.)

Recommendation: Change title as follows: Table 10.5: ETS Design Loading Rates

211 Table 10.5 [p.170]

Soil Category ETS Beds Loading Rate (mm/day)

1 [Note 1]

2 [Note 1 & 2]

3 [Note 1 & 2]

4 15

5 8 to 10

6 5

7 [Note 1]

Notes: 1. ETS/ASB systems are not normally used in Category 1 to 3 and are never appropriate in Category 7 soils. 2. Should ETS beds be used inn Category 2 or 3 soils, the loading rates for conventional beds apply (Table 10.3). This is because there will be minimal additional evapotranspiration in ETS compared top that in conventional beds in soils with high soakage characteristics.

This Table can be simplified and clarified, and Note 2 deleted. The allocation of

DLR at 15mm/day for soil Category 4 is at odds with the text in new 10.4.2 (where

5mm/day to 12mm/day is the DLR range given).

Recommendation: Simplify Table as follows as follows:

Soil Category ETS Beds Loading Rate

(mm/day)

1 Not Applicable

2 Not Applicable

3 [Note 1]

(15)

4 12

5 8 to 10

6 5

7 Not Applicable

Notes: 1. ETS systems are not normally applicable for Category 3 soils, but where used are to be loaded at the most conservative rate for conventional beds (Table 10.3).

212 Section 10.3.6

[p.170]

The “areal" loading rate (being design area plus the natural soil space between adjacent disposal beds) should be up to 3mm per day for primary effluent and up to 5mm/day for secondary effluent.

This needs clarification.

Recommendation: Change text as follows: An “areal" loading rate check should be undertaken to ensure that the total area enclosed by the ETS bed system (being the beds, the natural soil space between each bed, and a narrow border of not more than 500mm width around the outer edges of the bed system) is not loaded at more than 3mm/day for primary effluent and more than 5mm/day for secondary effluent.

TP58 3rd


48


213 Section 10.3.6

[p.170]

The concept of “areal” loading is important in the New Zealand context. This refers to the total load ----- beds or trances. For ETS on Category 6 tight clay ---- lower winter ET rates.

We do not need to repeat the explanation given (in the second sentence) as to what

“areal” loading is.

Recommendation: Delete second sentence, leaving the remaining two: The concept of “areal” loading is important in the New Zealand context. For ETS on Category 6 tight clay ---- lower winter ET rates.

214 Figure 10.4 [p. 171] Figure 10.4: Evapotranspiration Bed/Aerobic Seepage Bed Refer Item 210 above.

Recommendation: Change title as follows: Figure 10.4: Evapo-transpiration Seepage Bed – Typical Details

215 Figure 10.4 [p. 171] 100mm thick topsoil We need to emphasise the purpose of the crowned shape of the bed.

Recommendation: Add text as follows: 100mm thick topsoil cover over crowned surface of bed (to assist shedding of rainwater)

216 Figure 10.4 [p. 171] Vegetation on bed Item xii refers to bed mounding and planting with grass. Hence the diagram needs

altering to avoid giving impression of rank grass or other leafy plants.

Recommendation: Amend diagram.

217 Figure 10.4 [p. 171] 200mm of sand (0.5 -1) 200mm of ‘no fines’ (6 – 25)

Add units for sand/gravel gradings.

Recommendation: Add to text as follows: 200mm of sand (0.5 -1mm) 200mm of ‘no fines’ (6 – 25mm)

218 Figure 10.4 [p. 171] Subsoil perforated pipe 100mm diam. The design notes in new 10.4.3 iv state that dose loading is required. Hence we need

to amend diagram note.

Recommendation: Change text as follows: Distribution line to be LPP or LPED dose loaded by siphon or pump

219 Figure 10.4 [p. 171] Excavation width 1500mm This should be indicated as the desirable maximum width, although it is

acknowledged that greater widths can be used in the last sentence of Section10.4.3

Design Notes ---.

Recommendation: Change text as follows: Recommended maximum bed width 1500mm

220 Figure 10.4 [p. 171] Source: AS/NZS 1547:2000 AS/NZS 1547 has actually adopted (and acknowledged) this diagram from TP58,

2nd

Edition 1994. Hence we should not acknowledge the source as being AS/NZS

1547, or we are going around in circles.

Recommendation: Delete reference to Source: AS/NZS 1547:2000.

221 Section 10.3.7 [p.

171]

10.3.7 Bed Construction Details Title needs renumbering, and some reference to maintenance needs to be added.

Recommendation: Change title as follows 10.4.5 Bed Construction Details and Maintenance Requirements

TP58 3rd


49


222 Section 10.3.7 [p.

171]

The standard width for ETS beds is ------ on sloping sites (Figure 10.5). However pressure compensating dripper irrigation is a superior land disposal technique for all sites. It is recommended that beds ---- 1.5m centres are also common.

This thied sentence is no doubt added in here to reinforce the last sentence of the

first paragraph in the new Section 10.4.1. It looks out of place here. Adding a

separate paragraph and expanding may be best.

Recommendations: (a) Change text as follows The standard width for ETS beds is ------ on sloping sites (Figure 10.5). It is recommended that beds ---- 1.5m centres are also common.

(b) Add new paragraph: It is recommended that where ETS is being considered for a particular application, then a comparison be made with drip irrigation (PCDI). There may well be economies associated with the provision of secondary treatment and drip line irrigation, particularly as the “areal” loading rate check will designate a site area requirement for the ETS beds and 100% reserve area that takes up more lot area than that for PCDI.

223 Section 10.3.7 [p.

171]

Sand size for ETS beds of 0.5 to 1.0mm is recommended. It is important that sand size is not too fine so as to encourage evapotranspiration. For the Auckland area --- operating bed systems.

The reference in the second sentence re fine sand encouraging ET doesn’t make

sense.

Recommendation: Change text as follows Sand size for ETS beds of 0.5 to 1.0mm is recommended. It is important that sand size is not too fine, as although this will assist the capillary action which encourages evapotranspiration, fine sand reduces void storage space. On the other hand, if sand is too coarse then capillary action is inhibited. For the Auckland area --- operating bed systems.

224 Section 10.3.7 [p.

171]

[New paragraph on maintenance] Recommendation: Add new paragraph as follows The grass cover over the beds should be maintained regularly to avoid rank overgrowth and collapse onto the bed surfaces. Likewise, plantings between or downslope of ETS beds should be checked regularly to ensure optimum growth conditions for maximising evapo-transpiration assist.

225 Figure 10.5 [p. 172] Figure 10.5: ETS (EvapoTranspiration Seepage) Contour Beds Editing.

Recommendation: Change title to: Figure 10.5: ETS (Evapo-transpiration Seepage) Contour Beds

226 Figure 10.5 [p. 172] Aerobic Seepage Bed No. 1 Aerobic Seepage Bed No. 2

This term “aerobic seepage bed” is inappropriate (see Item 210 above).

Recommendation: Change text to: ETS Bed No. 1 ETS Bed No. 2

227 Section 10.4 [p 172] 10.4 MOUND LAND DISPOSAL SYSTEMS 10.4.1 General

We need to change numbering consequent on Item 189 above.

Recommendation: (a) Change title numbering to: 10.5 MOUND LAND DISPOSAL SYSTEMS 10.5.1 General

(b) Continue re-numbering throughout this and subsequent sections.

TP58 3rd


50


228 Section 10.4.2 [p

173]

10.4.2 Wisconsin Mound Systems Media Requirements All aggregate used for ---- and wastewater breakout from the sides. The sand fill grain size and infiltration capacity will determine the bed basal area. Use of local sand will reduce the cost against importation of sand. The use of highly permeable ---- slowly draining soils.

Note numbering change. Clarification is needed with these two sentences in the

centre of this paragraph.


10.5.2 Wisconsin Mound Systems Media Requirements All aggregate used for ---- and wastewater breakout from the sides. The sand fill grain size and infiltration capacity will determine the distribution bed basal area. Use of local sand will reduce the cost against importation of sand, but the sand specification must still be within that set out in Table 10.7. The use of highly permeable ---- slowly draining soils.

229 Table 10.6 [p. 173] Table 10.6: Comparison of Recommended Media Loading rates (in the Literature)*

Wisconsin Mound Distribution Media and Sand fill Media Loading Rates

Design Source Loading Rate* (l/m

2/d)

Sand Fill

AS/NZS 1547:2000 [Ref 1]

03 -1.0mm UC = 4 Max 50

USEPA 1980 * Crites [Ref 24 & 2]

Medium Sand >25% 0.25 – 2.0mm <30 – 35% 0.05 – 0.25mm <5-10% 0.002 – 0.05mm

Max 50

Converse [pers.com]

D10 0.3 – 0.5 UC 1 -4 Intermittent Sand Filter Grading

30 t0 40

Distribution Aggregate

AS/NZS 1547:2000 [Ref 1]

20 – 60mm non crushed

50

USEPA 1980 [Ref 2]

18 – 64mm

Notes * Loading Rates recommended by TP58 are presented in Table 10.7.

This table is not referred to within the text! First of all, what we are talking about

here is the loading into the distribution bed of aggregate over the sand fill media.

They are in fact the same thing, yet the table differentiates them into two groups.

Second, the asterisk is not needed if the Notes are better organised. [Note incorrect

reference to USEPA, bottom line.]

Recommendation: Change table and text to: Table 10.6: Comparison of Recommended Sand Fill Media and Distribution Bed Loading Rates (in the Literature)

Wisconsin Mound Distribution Bed Loading Rates

Design Source Media Specification Distribution Bed and Sand Fill Loading Rate

mm/day [Notes 1, 2 & 3]

Sand Fill

AS/NZS 1547:2000 [Ref 1]

03 -1.0mm UC = 4 Max 50

USEPA 1980 * Crites [Ref 24 & 2]

Medium Sand >25% 0.25 – 2.0mm <30 – 35% 0.05 – 0.25mm <5-10% 0.002 – 0.05mm

Max 50

Converse [pers.com] D10 0.3 – 0.5 UC 1 -4 Intermittent Sand Filter Grading

30 t0 40

Distribution Aggregate

AS/NZS 1547:2000 [Ref 1]

20 – 60mm non crushed [Note4]

USEPA 1980 [Ref 24]

18 – 64mm

Notes 1. The distribution bed loading rate is the same loading rate as passed through onto the surface of the sand fill used for secondary treatment. 2. Design loading rate mm/day equivalent to litres/m

2/day.

3. Loading Rates recommended by TP58 are presented in Table 10.7. 4. Maximum distribution bed loading rate 50mm/day

TP58 3rd


51


230 Section 10.4.2 [p

174]

Media Requirements There is some variation in then literature regarding suitable grain size distribution for use as sand fill media in mounds. AS/NZS 1547:2000 requires 0.3 t0 1.0mm however the relatively fine size increases the risk of a clogging mat ------ is only primary treated. Clogging of the infiltrative surface will ---- only provides limited wastewater treatment. USEPA (1980) [Ref 24] and Crites [Ref 2] recommend a maximum sand fill loading rate of 50mm/day for a sand having more than 25% of the grain size being 0.25 – 2.0mm.

First, this is the place to refer to Table 10.6. Second, the way the second sentence is

structured it seems to be implying that AS/NZS 1547 sand is too fine!

Recommendation: Change text to: There is some variation in the literature (Table 10.6) regarding suitable grain size distribution for use as sand fill media in mounds. It is important that fine grading is not used as this increases the risk of a clogging mat ------ is only primary treated. Clogging of the infiltrative surface will ---- only provides limited wastewater treatment. USEPA (1980) [Ref 24] and Crites [Ref 2] recommend a maximum sand fill loading rate of 50mm/day for a sand having more than 25% of the grain size being 0.25 – 2.0mm. AS/NZS 1547:2000 requires 0.3 to 1.0mm and uniformity coefficient less than 4.

231 Section 10.4.2 [p

174]

James Converse recommends --- 0.3 to 0.5mm [Ref 25] (refer Table 10.7). Converse also recommends a conservative sand fill wastewater loading rate to minimise the potential for development of a clogging layer. In the event that --- into the mound [Ref 25].

Table reference incorrect.

Recommendation: Change text to: James Converse recommends --- 0.3 to 0.5mm [Ref 25]. Converse also recommends a conservative sand fill wastewater loading rate (Table 10.6) to minimise the potential for development of a clogging layer. In the event that --- into the mound [Ref 25].

232 Section 10.4.2 [p

174]

Recommended media grains size and design sizing is based on the following table.

This needs tidying up.

Recommendation: Replace text with: Design sizing requirements for both the distribution bed area over the sand fill, and basal area over the prepared area on the natural ground surface, are set out below in Table 10.7.

TP58 3rd


52


233 Table 10.7 [p.174] Table 10.7: Mound Design Sizing Criteria

Parameter Design Specifications

Distribution Bed Course Media (20 – 60mm diameter

Loading rate based on sand fill media and not to exceed 50mm/day [Note 1]

Sand Media Loading Rate D10 0.3 – 0.5 UC = 1 -4 [Notes 2 & 3]

30mm/d for Primary Effluent [Note 4] 50mm/d for Secondary Effluent

Basal Soil Loading Rate Soil category 1 – 2 Soil category 3 – 4

35mm/day 12mm/day

Mound Toe Maximum Linear Loading rate

Max 50mm/linear metre/day

Notes: 1. Distribution media loading rate is determined by the sand fill media sizing, distribution media is to provide for even distribution of applied wastewater across the sand infiltrative surface. 2. D10 refers to the effective grain size that is the 10% by weight for a wet sieve analysis. 3. UC is uniformity coefficient defined by the D60/D10. 4. The application of primary treated effluent into the gravel distribution bed can result in clogging by bioslimes/clogging mat of the sand fill infiltration surface if the loading rate is to high. Finer fill will require lower application rates.

This table is a complete jumble, mixing loading rates and media sizing! The

distribution media loading rate is not determined by the sand fill media sizing, as

only one sizing is proposed. In addition parameters, loading rates and criteria are all

mixed up. Clarity required.

Recommendation: Replace text in table with:

Table 10.7: TP 58 Mound Media Specification and Loading Rate Sizing Criteria

Design For Design Specifications and Loading Rate

Distribution Bed Media

Aggregate Grading: 20 – 60mm Loading rate Not to exceed 50mm/day [Note 1]

Sand Media

Grading: D10 0.3 – 0.5mm UC = 1 -4 [Notes 2 & 3] Loading Rate

30mm/d for Primary Effluent [Note 4]

50mm/d for Secondary Effluent

Mound Basal Area

Loading Rate Soil category 1 – 2 35mm/day Soil category 3 – 4 12mm/day

Mound Toe Length

Maximum Linear Loading Rate 50mm/linear metre/day of width along downslope edge.

Notes: 1. Distribution media loading rate and the sand fill loading rate is the same. 2. D10 refers to the effective grain size that is the 10% by weight for a wet sieve analysis. 3. UC is uniformity coefficient defined by the D60/D10. 4. The application of primary treated effluent into the gravel distribution bed can result in bioslimes which can form a clogging mat on the sand fill infiltration surface if the loading rate is too high. Use of finer sand fill media than specified above risks clogging the filter, and will require a significantly lower application rate.

234 Section 10.4.2 [p

175]

Figure 10.6 and 10.7 show the design layouts for a Wisconsin Mounds on a flat site, and sloping site respectively. The designer should size the basal --- a toe extension should be installed. The toe width is determined by ground slope and the requirement for a maximum mound face angle of 1.3, (refer Appendix D, TS D-2). The designer should always --- check of the design for correctness.

Some clarification, correction and addition required here.

Recommendation: Add to and amend text as follows: Figure 10.6 and 10.7 show the design layouts for a Wisconsin Mounds on a flat site (11º or less), and sloping site (more than 11º) respectively. The designer should size the basal --- a toe extension should be installed. The downslope width I is determined by ground slope and the requirement for a maximum mound face angle of 1.3. (Appendix D, TS D-2 provides an example calculation). The toe length is L minus 2 times K. The designer should always --- check of the design for correctness.

235 Figure 10.6 [p. 176] Figure 10.6: Wisconsin Mound Details for Flat Site Should confirm what is meant by flat site:

Recommendation: Add to title: Figure 10.6: Wisconsin Mound Details for Flat Site [less than 11º]

TP58 3rd


53


236 Figure 10.6 [p. 176] Fill Add more detail here. This term has been very misinterpreted in the past when

designers do not read the text, and use any sort of fill including local soils.

Recommendation: Change text to: Sand media fill (as per Table 10.7)

237 Figure 10.6 [p. 176] Mound - D 600mm ---------- - I determined by ground slope and 1 in 3 mound face slope.

We need to indicate how K is determined.

Recommendation: Add text as follows: Mound - D 600mm ---------- - I determined by ground slope and 1 in 3 mound face slope.

- K determined by height of finished mound and 1 in 3 side slope.

238 Figure 10.7 [p. 177] Figure 10.7: Wisconsin Mound Details for Sloping Site Should confirm what is meant by sloping site:

Recommendation: Add to title: Figure 10.6: Wisconsin Mound Details for Sloping Site [greater than 11º]

239 Figure 10.7 [p. 177] Fill Add more detail here. This term has been very misinterpreted in the past when

designers do not read the text, and use any sort of fill including local soils.

Recommendation: Change text to: Sand media fill (as per Table 10.7)

240 Figure 10.7 [p. 177] Basal Area Sizing Flat site, enclosed by (W x L) Sloping site enclosed by (B [A + I])

Because this is a sloping site, the reference to flat site is superfluous.

Recommendation: Change text to: Basal Area Sizing Enclosed by (B [A + I])

241 Figure 10.7 [p. 177] Mound - D 600mm ---------- - I determined by ground slope and 1 in 3 mound face slope.

We need to indicate how K is determined.

Recommendation: Add text as follows: Mound - D 600mm ---------- - I determined by ground slope and 1 in 3 mound face slope.

- K determined by height of finished mound and 1 in 3 side slope.

242 Section 10.4.3 [p.

178]

10.4.3 At-Grade [Fill] System Remember, the numbering changes!

Recommendation: Re-number as follows: 10.5.3 At-Grade [Fill] System

243 Section 10.4.4 [p.

178]

10.4.4 Mound Construction The natural ground surface ----- cultivator (not rotary hoe). Sand fill of 0.3 to 1.0mm size (uniformity coefficient 4) should be carefully spread ---- or light machine compaction.

Remember, the numbering changes! Note also that the sand grading in here is the

AS/NZS 1547 grading rejected in favour of the Converse grading. The Converse

grading seems to be a finer sand than that in AS/NZS 1457, and this appears to be

why lower design loading rates are required.

Recommendation: Change to following: 10.5.4 Mound Construction The natural ground surface ----- cultivator (not rotary hoe). Sand media fill of 0.3 to 0.5mm size (uniformity coefficient 1 to 4) should be carefully spread ---- or light machine compaction.

TP58 3rd


54


244 Section 10.5 [p. 179] 10.5 BOTTOMLESS SAND FILTER These loading rates and treatment ---- to the underlying soil conditions. Bottomless sand filter loading rates are higher than those for discharge control trenches in Category 1 soils as bottomless sand filters are a specifically engineered treatment and land disposal system, involving timer dose loading with specifically graded sand, whereas discharge control trenches are not. Such systems should only be designed and installed by experienced professionals.

We should refer the reader back to the sand grading requirements, and also make

changes related to relationship between bottomless sand filters and discharge control

trenches and beds (see Item 167 above).

Recommendation: Change to following: 10.6 BOTTOMLESS SAND FILTER These loading rates and treatment ---- to the underlying soil conditions. Bottomless sand filter loading rates are higher than those for discharge control trenches and beds in Category 1 and 2 soils ( Section 10.1.4) as bottomless sand filters are a specifically engineered treatment and land disposal system, involving timer dose loading with specifically graded sand (see grading in Table 7.6), whereas discharge control trenches and beds are not. Such systems should only be designed and installed by experienced professionals.

249 Section 10.6 [p. 179] 10.6 INFILTRATION SYSTEMS Remember, the numbering changes!

Recommendation: Re-number as follows.: 10.7 INFILTRATION SYSTEMS

250 Section 10.7 [p. 181] 10.7 DEEP BORES Remember, the numbering changes!

Recommendation: Re-number as follows: 10.8 DEEP BORES

251 Section 10.7 [p. 181] 10.7.1 General Deep bores may have hydraulic applicability where permeable subsoil layers or fractured rock exists at depth under poorly draining clayey upper soil layers but are not environmentally sustainable. However, a specialist soils/geological consultant must be ------.

It is not clear what the “are not environmentally sustainable” refers to. Clarify.

Recommendation: Clarify as follows: 10.8.1 General Deep bores may have hydraulic applicability where permeable subsoil layers or fractured rock exists at depth under poorly draining clayey upper soil layers. They should only be utilised in situations where they can be shown to be environmentally sustainable. A specialist soils/geological consultant must be ------.

252 Section 10.7.4 [p.

183]

10.7.4 Installation and Operation Groundwater bore installation details are provided in Figure 10.9.

This gives the impression it is a water supply bore.

Recommendation: Change text as follows: 10.8.4 Installation and Operation Installation details for deep bore effluent disposal are provided in Figure 10.9.

TP58 3rd


55


253 New Section 10.9

[p.183]

Table 10.4 on page 168, and Item 199 above. The use of a revised version of Table 10.4 is more appropriate here in summing up

this whole Chapter 10.

Recommendation: Insert revised Table 10.4 here, and provide accompanying text

as follows [Note that the revised Table 10.4 is provided on page 45 above.]:

10.9 Land Disposal – Summary of Systems

The application of the range of land disposal systems covered in this Chapter is set out in Table 10.4. Further summary details related to recommended loading rates for individual systems and soil categories are set out in Appendix D as follows:

Table TS5-1: Soil Category and Applicable Land Disposal Method (a repeat of the Table 10.4).

Table TS5-2: Summary of Land Disposal Methods and Recommended Loading Rates

vs Soil Category

254 Chapter 11 [p. 184

to 200]

Whole text. Editing required to deal with spelling, punctuation and structure in several places.

255 Section 11.2 [p. 186] [Ref 28] This reference relates to a paper on “Peat Treatment of Septic Tank Effluent”. Is this

the correct citation related to the material in this paragraph?

256 Section 11.2 [p. 186] (The latter is discussed in more detail in Section 12.2.2.2 and in Technical Sheets 1-5 and I-6 in Appendix I.)

Editing.

Recommendation: Change text to: (The latter is discussed in more detail in Section 12.2.2 and in Technical Sheets I-5 and I-6 in Appendix I.)

257 Section 11.3 [p. 186] The Ministry of Health drinking water standard for nitrate in water is 50g/m

3 nitrate [Ref 45], (with “nitrate” meaning “total nitrogen”

(being organic and inorganic) in this context). This is equivalent to 10g/m

3 nitrate nitrogen (NO3-N) when only referring to the nitrate

form [Ref 29].

This statement in brackets attempting to explain nitrogen relationships is totally

incorrect.

Recommendation: Change text to: The Ministry of Health drinking water standard for nitrate in water is 50g/m

3 NO3 [Ref 45]. The

nitrogen in nitrate is around 1/5th of the total content by weight (oxygen being 4/5

th ).This has

lead to the limits for dinking water often being expressed in terms of the nitrogen component of nitrate at 10g/m

3 nitrate nitrogen (NO3-N) [Ref 29].

258 Section 11.4.2.2 [p.

188]

11.4.2.2 Nitrogen Reduction by Primary Septic Tank Treatment Gunn [Ref 29] refers to other United States researchers that suggest reductions up to 33% in a septic tank, but recommends a conservative approach would be to assume there is no significant reduction via septic tank treatment.

There are two items related to “source removal” in Table 11.1 that are out of context

with the secondary treatment discussion in Section 11.4.2.3. These can be relocated

and added in here as text (see Item 261 below).

Recommendation: Add text as follows (but check out and clarify what is meant by

“source separation with treatment applied to both systems and then recombined”): Gunn [Ref 29] refers to other United States researchers that suggest reductions up to 33% in a septic tank, but recommends a conservative approach would be to assume there is no significant reduction via septic tank treatment. The USEPA indicates [Ref 3] that source separation and removal prior to entering septic tank flows can remove 60 to 80%, and that source separation with treatment applied to both systems and then recombined can achieve 40 to 60% removal.

TP58 3rd


56


259 Table 11.1 [p. 189] Table 11.1: Typical Nitrogen Removal Ranges for well Managed Systems

The title needs amending to reflect the text.

Recommendation: Change title to: Table 11.1: Typical Nitrogen Removal Ranges for Well Managed Secondary Treatment Systems

260 Table 11.1 [p. 189] Septic Tank Fixed Film System, with recycle to Septic Tank or Anaerobic Upflow Filter (equivalent to TF-AWTS**)

The term “trickling filter” has been revised to “biofilter” (see Item 56 above).

Recommendation: Change text as follows: Biofilter Fixed Film System, with recycle to Septic Tank or Anaerobic Upflow Filter (equivalent to BF-AWTS**)

261 Table 11.1 [p. 189]

Source Separation and Removal

60 – 80

Source Separation with treatment applied to both systems and then recombined.

40 – 60

This information is quite out of context with the material on secondary treatment

removal in this section. The “Source Separation with treatment applied to both

systems and then recombined” needs to be clarified as to what “treatment” is

involved in the process of separation and re-combination of flows.

Recommendation: Relocate back as text into Section 11.4.2.2 (see Item 258

above) and thus delete from this Table 11.1

262 Table 11.1 [p. 189] ** TF-AWTS stands for Trickling Filter – Aerated Wastewater Treatment System and is covered in section 7.3.5.

See Item 260 above.

Recommendation: Change text as follows: ** BF-AWTS stands for Biofilter – Aerated Wastewater Treatment System and is covered in section 7.3.5.

263 Section 11.5.4 [p.

195]

11.5.4 Specialised Options for Phosphorus Removal The Australian “Ecomax” system for on-site wastewater phosphorus removal has

been used over several years now and is available through agents in NZ.

Do you want to make reference to it here? The company has sought my advice about

demand in NZ, and I have not been very encouraging, as in fact there is no demand.

264 Section 12.2.3 [p.

206]

Regular checks of the septic tank outlet filter. Outlet filters are defined ---- they should be wherever practicable (refer section 7.2.6). These should be checked monthly and removed and rinsed (hosed down) whenever the slime build-up stars to block the filter orifices. The wastewater discharge should be drained back into the septic tank or into a sewerage gully trap or onto ground in a densely vegetated area unlikely to be accessed by children or animals and then retrofitted into the tank.

The content of this paragraph is misleading and inappropriate, with the last sentence

totally confusing. The fact is effluent outlet filters do not need checking monthly,

and cleaning should be left to the servicing contractor during pumpout. If slime does

clog to an unacceptable degree, this will be signalled by backup in the incoming

drainage lines, thus alerting to the need for hosing down. There is no reason to hose

down to any other location than back into the septic tank (definitely not onto the

ground in any location unless into a hole which is then covered with soil). [Note

change in section number to 7.2.7.]

Recommendation: Amend and change text as follows: Regular checks of the septic tank outlet filter. Outlet filters are defined ---- they should be wherever practicable (refer section 7.2.7). These should be checked during tank pumpout events and if necessary excess slime growths hosed down back into the septic tank. Under no circumstance should the filter unit be hosed clean, as slime growth on the filter surfaces and slot openings contributes to controlling the filtering effectiveness. If excess slime develops to the extent of restricting flow passage through the filter openings, then backup in the incoming sewer line at the gully traps will indicate the need to call service personnel to deal with the matter.

TP58 3rd


57


265 Section 12.2.4 [p.

206]

12.2.4 Secondary Treatment Systems Maintenance AWTSs typically use a suspended growth treatment process (similar to activated sludge extended aeration) or a fixed film treatment process (similar to trickling filter).

We need to adjust this sentence to fit earlier recommended changes related to

terminology (see Item 56 above).

Recommendation: Amend as follows: AWTSs typically use a suspended growth treatment process (similar to activated sludge extended aeration) or a fixed film treatment biofilter process (similar to the earlier “trickling filter” system).

266 Section 12.2.5 [p.

206/207]

12.2. 5 Other Treatment System Maintenance In all cases, maintenance must be undertaken in accordance with the ---- the respective parts of Sections 7.6 to 7.9.

Referral to Section numbers incorrect.

Recommendation: Change to: In all cases, maintenance must be undertaken in accordance with the ---- the respective parts of Sections 7.6 to 7.8.

267 Section 12.2.8 [p.

208]

12.2.8 Management Plans (b) Design Discharge Volume: Details of the scope ------- corresponding design discharge volume.

The concept of a “loading certificate” is recommended for consideration. Where

“maintenance checks” are often referred to as a “WOF” (warrant of fitness), the

parallel of a “Loading Certificate” has significant value in alerting the owner/user to

the capacity of their system.

Recommendation: Add a note here as follows: (b) Design Discharge Volume: Details of the scope ------- corresponding design discharge volume. [Note: A “Loading Certificate” should be prepared and issued to the owner/occupier of the dwelling for display in a prominent location such as the toilet compartment(s) and/or laundry area. The “Loading Certificate” should summarise the detail provided in this section of the Management Plan, including:

Design occupancy (persons)

Design daily flow capacity.

Consequences of daily occupancy and daily design flows being exceeded on both a temporary basis, and a permanent basis.]

TP58 3rd


58


268 Section 12.2.9 [p.

210]

12.2.9 System Monitoring Flow Monitoring The most common ---- volumes exceeding design flow volumes. The meter should then be read at times of peak occupancy to provide for the home user/owner to control of actual water usage as required. Most owners ------.

This is not the purpose of flow metering. Can you imagine the owner coming into

the house after having read the meter, and saying, “Sorry, but three of you visitors

will have to leave – we are exceeding the design flow for our on-site wastewater

system” or “Sorry, no baths, showers or laundry use during your stay – we are

exceeding the design flow for our on-site wastewater system”? On-site wastewater

systems have significant buffering capacity to deal with peak high load situations

for short time periods. What the meters are there to do is record the aggregate flow

over a reasonable time frame (such as three monthly) to them match with the

“Loading Certificate”. It is long-term high load situations that need to be dealt with,

and the owner will already be aware of potential high flows from the occupancy

level. It is determining whether the prolonged exceedances of occupancy above the

“Loading Certificate” levels is affecting the overall system that flow meter records

can help assess in conjunction with land application area inspections.

Recommendation: Change text as follows: The most common ---- volumes exceeding design flow volumes. The meter should then be read on a routine basis (for example, three monthly) in order to review compliance with the “Loading Certificate” so as to alert the owner/occupier to potential overload conditions on the treatment and land disposal area. Most owners ------.

269 Section 12.2.9 [p.

210]

Discharge Quality Monitoring Monitoring of treated and disinfected wastewater prior to reuse is critical ------- or potential system failure. The recommended treated wastewater quality monitoring specifications are detailed in Section 7.8. In the case of -----.

There are no monitoring specifications in Section 7.8, so what is being referred to

here? Is it general treated effluent quality, or reuse effluent quality?

Recommendation: Clarify text and reference back to “monitoring specifications”.

270 Section 12.2.10 [p.

211]

12.2.10 Remedial Procedures for System Failure Figure 12.1 outlines a 5 step ------.

Table, not Figure.

Recommendation: Change text: Table 12.1 outlines a 5 step ------.

271 Table 12.1 [p. 212] Table 12.1: STEP PROCEDURE --- FAILURE

Identify Solutions and Initiate Corrective Actions

Reduce Flows Improve water construction

What does this mean?

Recommendation: Change text?:

Improve water use reduction measures

272 Glossary [p. 213] Aerated wastewater treatment plant/system (AWTP or AWTS) A mechanical on-site treatment --- (similar to activated sludge extended aeration) but can also involve or a fixed film (air vented fixed media) biological filtration treatment process, similar to trickling filter. These are ------.

Since AWTP is not used throughout the text, and AWTS is, delete AWTP. Also, in

terms of Item 265 above we can make minor changes here.

Recommendation: Change text to: Aerated wastewater treatment system (AWTS) A mechanical on-site treatment --- (similar to activated sludge extended aeration) but can also involve or a fixed film (air vented fixed media) biological filtration (biofilter) treatment process, originally termed “trickling filter”. These are ------.

TP58 3rd


59


273 Glossary [p. 214] Biochemical Oxygen Demand (BOD) A commonly used gross measurement ---- expressed in milligrams per litre (mg/L), required by bacteria ---- during oxidation.

Reference to units inconsistency is made elsewhere (see Item 83 above). Note also

that the five day BOD needs to be referred to.

Recommendation: Change text to: Biochemical Oxygen Demand (BOD and BOD5)) A commonly used gross measurement ---- expressed in grams per cubic metre (g/m

3), required

by bacteria ---- during oxidation. BOD5 refers to the results of the test which is carried out over five days at constant temperature of 20 ºC.

274 Glossary [p. 214] Centralised Wastewater Treatment System (CWTS) Should this be as follows (see Item 6 above)? Centralised Wastewater Management System (CWMS)

275 Glossary [p. 214] De-centralised Wastewater Treatment System (DWTS) Should this be as follows (see Item 6 above)? De-centralised Wastewater Management System (DWMS)

276 Glossary [p. 215] Design irrigation rate (DIR) The loading rate ----- secondary quality. It is expressed in L/m

2/week or mm/week. If a spray ------ subject to continuous

disinfection.

DIR does not seem to be used herein, and irrigation loading rates are given in l/m2/d

(mm/d) and not per week.

Recommendation: Amend and expand text to: The loading rate ----- secondary quality. It is often expressed in l/m

2/week or mm/week, but in

this edition of TP58 daily irrigation loading rates are used (l/m2/day or mm/day). If a spray ------

subject to continuous disinfection.

277 Glossary [p. 215] Dissolved Oxygen (DO) The oxygen ---- in milligrams per litre (mg/L), parts per million (ppm), or percent saturation.

Reference to units inconsistency is made elsewhere (see Item 83 above).

Recommendation: Amend to: The oxygen ---- in grams per cubic metre (g/m

3) [formally milligrams per litre (mg/L) or parts

per million (ppm)], or percent saturation.

278 Glossary [p. 216] Effluent filter ( also called an Outlet filter and an Outlet solids control device)

Is the term Effluent Outlet Filter not also relevant?

Recommendation: Amend to?: Effluent outlet filter ( also called an “outlet filter” and an “outlet solids control device”)

279 Glossary [p. 217] Evapotranspiration-seepage bed Recommendation: Amend to: Evapotranspiration-seepage (ETS) bed

280 Glossary [p. 217] Hydrologic conductivity As applied to soil, the ability of the soil to transmit water in liquid form through pores.

Recommendation: Amend spelling and amplify as below: Hydraulic conductivity As applied to soil, the ability of the soil to transmit water in liquid form through pores. Measured with constant head permeability apparatus, and specified as Ksat in m/day.

281 Glossary [p. 217] Land Disposal system (Also called Application System) Recommendation: Amplify and amend to: Land Disposal System (also called Land Application System)

282 Glossary [p. 217] Long term Acceptance Rate The maximum rate that a ----- evaporation and evapotranspiration.

Should a fuller explanation be provided here?

Recommendation: Amplify and amend to: Long Term Acceptance Rate (LTAR) The maximum rate that a ----- evaporation and evapotranspiration. LTAR s controlled by the clogging slimes or biomat (biological growths) generated by interaction of effluent organic and nutrient matter with soil bacteria, and which lower the infiltration rate of effluent from the land disposal system into the surrounding natural soil. Design loading rates and design irrigation rates should always be lower than the biomat LTAR in order to avoid effluent accumulation in the land application area, and possible “breakout” to ground surface.

TP58 3rd


60


283 Glossary [p. 218] On-site wastewater treatment system (OWTS) Should this be as follows (see Item 6 above)? On-site wastewater management system (OWMS)

284 Glossary [p. 218] Outlet filter (Also call Effluent filter) See Item 278 above.

Recommendation: Change to: Outlet Filter (also called Effluent Outlet Filter)

285 Glossary [p. 219] Population equivalent The ratio of the total quantity of wastewater produced to that defined as being equivalent to that produced by one person.

Simplification required.

Recommendation: Change to: The ratio of the total quantity of wastewater produced to that defined as being produced from one person.

286 Glossary [p. 219] Recirculating Packed Bed Reactor A multiple pass sealed reactor media bed (refer Packed Bed Reactor). The recirculating ratio is typically at one to three to one to five.

Recirculation ratio is expressed the other way around, that is recirculation flow to

daily through flow. [Note: The term “sealed” is used here as elsewhere related to

packed bed reactors. What does this mean? None of these units is “sealed” in the

normal sense.]

Recommendation: Change to: A multiple pass reactor media bed (refer Packed Bed Reactor). The recirculating ratio is typically between three to one to five to one.

287 Glossary [p. 220] Soil absorption zone Recommendation: Delete the repeated last sentence.

288 References [p. 224] 16 New Zealand Waste Water Association, New Zealand

Recommendation: Change to: New Zealand Water & Wastes Association, New Zealand

289 References [p. 224] 33 No Publisher identified.

290 Contents Pages Recommendation:

The Contents Pages should be expanded to include:

Sub-sub-heading numbering and topics;

List of Tables;

List of Figures; and

Details of contents of Appendices and page numbers.

In addition, the whole document would be enhanced by provision of a topic index

against section numbering and page numbers.

To Be Continued: Part 2: Appendices

***********************************************

Documents

A COMMENTARY on ARC TP 58, 3rd Edition 2004 - WordPress.com · 12/2/2013 · Section 2.1.3 [p. 8] states that: TP 58 is not a statutory document in itself, under the Resource Management