Investigation of decentralised wastewater recycling for ... · Perth must move towards closing the cycle of water. One method of doing this is by creating decentralised wastewater

'Investigation of decentralised wastewater recycling for

irrigation of public open space in urban villages – Development

of a model for reliable management systems and improved

protection of public health and the environment within the Perth

Metropolitan Region'

Shaun Jamieson B.Sc (Environmental Technology)

Honours Thesis

Supervised by Dr. Martin Anda

Co-supervisor Prof. Goen Ho.

School of Environmental Science, Murdoch University

November 2006

Declaration This thesis is presented to complete the requirements of a Bachelor of Science

(Environmental Science) with Honours.

I declare that the work compiled within this thesis is based on my own account of

research conducted at Murdoch University, Western Australia.

Shaun Jamieson July 05, 2006

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Papers Arising from this study A Technology Database for Onsite Wastewater Management Systems. Paper presented at “Turning Waste to Water” seminar in Denmark, Western Australia, December 2005. A Technology Database for Decentralised Wastewater Recycling Systems. Paper presented at the International Conference on Decentralised Water and Wastewater Systems Fremantle. Western Australia, July 2006.

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Abstract The incorporation of decentralised wastewater recycling systems on the ‘urban

village’ or ‘subdivision’ scale can play a major role in the move towards water

sensitive urban development. As well, this approach can potentially provide a range of

sustainable development benefits over conventional centralised sewerage systems.

While decentralised wastewater recycling can present many environmentally

sustainable benefits, the successful implementation of such system requires an

integrated consideration for four interrelated technical elements:

• Public health requirements;

• Environmental requirements;

• Appropriate technology selection; and

• Management system development.

A Technical Element Model (TEM) was developed that identifies each technical

element component, how they interconnect, and where they apply within the various

implementation process steps. The model is specifically characterised towards

decentralised wastewater recycling for irrigation of public open space in urban

villages of the Perth Metropolitan Region, however the fundamental components of

the model can be adapted to meet a range of wastewater recycling situations. The

TEM can potentially assist with the employment of this water and energy saving

approach, however, further development is required before a real life application.

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Table of Contents Abstract .........................................................................................................................iv Table of Contents...........................................................................................................v List of Figures..............................................................................................................vii List of Tables ..............................................................................................................viii List of Abbreviations .....................................................................................................x Acknowledgments.........................................................................................................xi 1. Introduction................................................................................................................1

1.1 Background ..........................................................................................................1 1.2 Need for study......................................................................................................2 1.2 Research process, aims and objectives. ...............................................................2

1.2.1 Aim ...............................................................................................................3 1.2.2 Objective .......................................................................................................3 1.2.3 Research process...........................................................................................4

2. Literature Review.......................................................................................................5 2.1 Sustainable wastewater management...................................................................5 2.2Domestic wastewater ............................................................................................7

2.21 Sources and streams.......................................................................................7 2.2.3 Nutrients........................................................................................................9

2.3 Wastewater treatment.........................................................................................10 2.4.1 Primary........................................................................................................10 2.4.2 Secondary....................................................................................................11 2.4.3 Advanced ....................................................................................................11

2.4 Water management within the Perth Metropolitan Region ...............................12 2.4.1 Water use ....................................................................................................12 2.4.2 Wastewater management ............................................................................13 2.4.3 Nutrient issues.............................................................................................15 2.4.4 Policies, Regulations and Standards ...........................................................16

2.6 Summary ............................................................................................................17 3. Project Objectives and Methods ..............................................................................18

3.1 Aims and objectives...........................................................................................18 3.1.1 Technical requirements...............................................................................19 3.1.2 Appropriate technology choice ...................................................................20

3.2 Methods..............................................................................................................22 3.2.1 Technical requirements...............................................................................22 3.2.2 Appropriate technology choice ...................................................................22 3.2.3 Decision support tool model .......................................................................23

4. Technical Requirements...........................................................................................24 4.1 Public health protection .....................................................................................24

4.1.1 Sewage ........................................................................................................24 4.1.2 Greywater....................................................................................................28

4.2 Environmental Protection ..................................................................................29 4.2.2 Draft National Guidelines for Water Recycling .........................................32 4.2.3 Minimum setback distances........................................................................40 4.2.3 Water Quality Protection Notes ..................................................................40

4.3 Management systems .........................................................................................43 4.3.1 Risk management framework approach......................................................43 4.2.3.2 Nutrient Irrigation Management Plan ......................................................45

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4.4 System design and implementation process ......................................................46 5. Appropriate Technology Selection ..........................................................................49

5.1 General configuration ........................................................................................50 5.2 Scale of collection..............................................................................................50 5.3 Recycling system components...........................................................................52 5.4 Evaluation system ..............................................................................................53

5.4.1 Method ........................................................................................................53 5.4.2 Results.........................................................................................................57

6. Technical Elements Model ......................................................................................61 7. Discussion ................................................................................................................65

7.1 Significant findings............................................................................................65 7.1.1 Technical elements model...........................................................................65 7.1.2 Appropriate Technology Selection .............................................................67

7.3 Further development ..........................................................................................69 8. Conclusion ...............................................................................................................72 References....................................................................................................................73 Appendix A – Fit for Purpose Guidelines for Recycled Water ...................................76 Appendix B – Management system elements explained (EPHC, 2005) .....................79 Appendix C – Treatment type descriptions .................................................................90 Appendix D – Evaluation criteria description .............................................................91

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List of Figures Figure 1 Various sources of household water including black, grey, brown and yellow,

going to deep sewerage (diagram modified from IETC, 2002) .............................8 Figure 2 Average single residential household water usage in Perth (source: WC,

2005) ....................................................................................................................13 Figure 3 Elements of the framework for management of recycled water quality and

use (EPHC, 2005) ................................................................................................45 Figure 4 A comparison of the ATU treatment types available on a cluster scale. (Note:

lower values areas are best). ................................................................................58 Figure 5 A comparison of the ATU treatment types available on a cluster scale. (Note:

lower values areas are best). ................................................................................59 Figure 6 The two employment phases of decentralised wastewater recycling system.

..............................................................................................................................61 Figure 7 The five steps of the implementation process and the interconnection with

the technical elements ..........................................................................................63 ure 8 The environmental requirements component of the model ................................64 Figure 9 The public health requirements component of the model ......................64

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List of Tables Table 1 Factors affecting the decision to select a decentralised or centralised

wastewater system (Ho, 2005, p16).......................................................................6 Table 2 Comparison of the characteristics of untreated black, grey, yellow, and brown

water (Source: Huber (2004) and DoH (2005)) .....................................................8 Table 3 The benefits and limitations of centralised sewerage networks in comparison

to decentralised systems.......................................................................................14 Table 4 A summary of two classes within the Fit for Purpose Guidelines for Water

Recycling that are applicable for wastewater recycling via POS irrigation ........26 Table 5 A revised version of the Fit for Purpose Guidelines including information

from the Draft National Guidelines for Water Recycling and to be used in the technical elements model.....................................................................................27

Table 6 A revised version of the Fit for Purpose Guidelines for Water Recycling for greywater to be used in the technical elements model.........................................28

Table 7 The indicative drainage classes specified in the ASNZS 1547, and the new drainage classes adopted in the technical elements model. .................................30

Table 8 The new maximum design irrigation rates for the technical elements model...............................................................................................................................31

Table 9 A list of key environmental hazards associated with domestic wastewater ..32 Table 10 Environmental factors, hazards and effects that need to be considered when

determining environmental risk. ..........................................................................33 Table 11 The minimum setback distances or ‘buffer zones’ to be applied in the

technical elements model.....................................................................................40 Table 12 Vulnerability to eutrophication of downstream surface water bodies and

vulnerability classes as specified by Department of Environment Water Quality Protection Notes...................................................................................................41

Table 13 The maximum inorganic nitrogen and phosphorus for the vulnerability categories as specified by Department of Environment Water Quality Protection Notes ....................................................................................................................41

Table 14 The five stages of a decentralised wastewater recycling implementation process (ASNZS 1547) ........................................................................................47

Table 15 The three available scales of decentralised wastewater recycling................51 Table 16 The general concept behind the scale of collection selection model ............51 Table 17 The various wastewater treatment type groups and there appropriateness for

village or cluster scale decentralised wastewater recycling in urban villages .....52 Table 18 The groups, categories and subcategories of the cataloguing system (A

description of each category and sub category is provided in Appendix C) .......52 Table 19 A brief description and associated measurement values used in the

evaluation scoring system (Appendix D).............................................................54 Table 20 An example of the scoring sheet used for the treatment type: Activated

Sludge (continuous aeration) on a cluster scale (Appendix E) ............................54 Table 21 The nutrient risk allocated to the four soil vulnerability categories (Table12).

..............................................................................................................................56 Table 22 The organic and nutrient impact evaluation scores for the different ATU

treatment types (Note: lower values are best)......................................................57 Table 23 The ATU treatment types selected for cluster scale application Note: the first

treatment type listed in each section is the first recommendation, and so on).....59

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Table 24 The ATU treatment types selected for village scale application Note: the first treatment type listed in each section is the first recommendation, and so on).....60

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List of Abbreviations AS Activated sludge ATU Aerobic treatment unit BOD Biological oxygen demand DeWaTARS Decentralised Wastewater Treatment and Recycling Systems EDST Electronic decision support tool FB Fluidised Bed MBBR Moving bed bioreactor MBR Membrane bioreactor PF Percolating filter PMR Perth Metropolitan Region RBC Rotating biological contactor SAF Submerged aerated filter SS Suspended solids TN Total nitrogen TP Total phosphorus

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Acknowledgments I would like to thank my supervisors Dr. Martin Anda and Prof. Goen Ho who

provided a vast array of guidance and support throughout the duration of the thesis.

Thanks also to my sponsors, the Premiers Water Foundation and National Lifestyle

Villages. I would also like to give recognition to my colleagues at the Murdoch

University Environmental Technology Centre, who have offered me extensive

technical advice and personal encouragement.

My biggest acknowledgment goes to my wonderful family and partner Amy. You

guys have given me the strength to carry on through the toughest months of my life.

Amy you have been there by my side throughout the duration of my tertiary schooling

and your friendship and support has been invaluable. To my direct family Lyn, Ross,

Brayden, Rhys (dec.), and Tori – for you I have strived to achieve, thank you.

The Grantee appreciates the assistance provided by the Premier’s Water Foundation. The views expressed are not necessarily the views of the Government of Western Australia, nor the Premier’s Water Foundation.

Decentralised Wastewater Recycling Hons Thesis Shaun Jamieson 2006

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1. Introduction

1.1 Background

Perth, Western Australia’s largest city is under increasing pressure to implement a

more sustainable means of water supply and use. The coastal city is expanding

rapidly in both population and geographical size (EPA, 2005), while annual rainfall is

variable and gradually decreasing (WC, 2005). On top of the supply issues Perth is

continuing to implement a centralised approach to wastewater sanitation, which

combines many wastewater streams before treatment and disposal to ocean outfall

(EPA, 2005). This creates an open cycle system that has many sustainability issues

including inefficient use of potable water supplies, loss of freshwater resources and

nutrients, pollution of the receiving water bodies, as well as the need for high energy

infrastructure (Ho and Anda, 2004).

With the continuing increase in water demand and declining rainfall it is clear that

Perth must move towards closing the cycle of water. One method of doing this is by

creating decentralised wastewater systems that treat and reuse the water on a much

smaller scale than the traditional approach (Fane et al. 2002). The recovered water can

be used for urban non-potable requirements such as irrigation, toilet flushing and

washing water, as well as a range of non-urban agricultural and industrial

applications. Reuse of domestic wastewater can reduce the use of valuable potable

water, help to recycle nutrients, and lower the amount of wastewater required for

disposal into the environment (Ho and Anda, 2004).


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1.2 Need for study

While wastewater recycling can present a range of benefits there are a number of

factors which are currently limiting its application within the Perth Metropolitan

Region (PMR). The Metropolitan Sewerage Policy (WAGov 1996) effectively

prevents the implementation of decentralised systems within the metropolitan area,

which is largely due to concerns regarding groundwater protection and management

issues. As a result, there is currently a limited application of decentralised wastewater

recycling within urban villages of the Perth Metropolitan Region. However, there is

some scope within this policy for trial of innovative systems under special approval,

which could be used to demonstrate to the associated governing authorities the

technical performance of such systems.

The trial systems are likely to involve new or existing residential housing

developments, referred to as urban villages, which are not currently serviced by

Metropolitan Sewerage Network. While there are many ways to achieve decentralised

wastewater recycling, it is likely that irrigation onto areas of public open space will be

the most achievable method in the short to medium term due to less likely public

health risk and current regulatory framework (DoH, 2005). Investigation into the

technical requirements of this wastewater recycling approach is needed to ensure that

the implemented systems consider the ongoing protection of public health and the

environment.

1.2 Research process, aims and objectives.

The research question for this thesis is:


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Can the processes for the successful implementation of decentralised

wastewater recycling systems within urban villages of the Perth Metropolitan

Region be clearly identified and applied to a model that describes the required

technical elements?

From this question the aims, objectives and research process are developed.

1.2.1 Aim

The aim of the project is to investigate the technical elements associated with the

successful implementation of an urban village wastewater recycling system within the

PMR, for which a means can be developed to assist with the identified aspects. The

technical elements include the technical requirements/obligations to ensure reliable

management systems and improved protection of public health and the environment,

as well as the appropriate technology selection to meet the specified technical

requirements.

1.2.2 Objective

The objective of the project is to develop a model to assist with the comprehensive

implementation of wastewater recycling systems, to ensure that all public health and

environmental requirements are fulfilled in an ongoing manner.

The model will:

Be specifically characterised towards urban village recycling of wastewater

via irrigation onto public open space within the Perth Metropolitan Region;

Identify and describe the associated technical requirements for reliable

management systems and protection of public health and the environment;


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Recommend the appropriate wastewater recycling technologies needed to

achieve the specified technical requirements; and

Determine the interrelations between the identified requirements and how they

can be applied to the implementation process.

1.2.3 Research process

In order to develop a model to describe the associated technical requirements and how

to meet those requirements, the following research processes are required:

1. Investigate the current water management situation within the PMR and the

issues associated with wastewater recycling, as well as existing models and

tools used for wastewater recycling implementation.

2. Identify and analyse the technical requirements for decentralised wastewater

recycling onto POS within urban villages of the PMR.

3. Identify and analyse a range of technologies to determine the most appropriate

wastewater recycling system components to meet the acknowledged technical

requirements;

4. Develop the findings into a model that will systematically determine the

technical requirements and appropriate technologies for a given situation.


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2. Literature Review The Literature Review includes a critical review of number of topics and ideas to

provide a background to the overall investigation. It examines the concepts behind

sustainable wastewater management and looks at domestic wastewater characteristics

and how they are treated. The current domestic water supply, disposal and recycling

situation within the Perth Metropolitan Region is also reviewed.

2.1 Sustainable wastewater management

“Sustainability requires us to equally consider economic, environment

and social factors in any development effort.” Ho, 2005, p16.

“.. the pursuit of Sustainable Development has become a goal common

to environmentalists, economists, development theorists, governments,

and even many industrialists.” Anda, 1997, p5.

The major cities of Australia continue to develop large centralised sewer networks

with the belief that they are cheaper and easier to operate than small localised systems

(Rule and Oliver, 1997). As well, this approach has historically provided public

health benefits and a convenient household service (Ho, 2005). However, new and

improved wastewater treatment options that can be applied on a decentralised scale

are becoming more cost effective, as well as providing other sustainability benefits

(Ho, 2005; Cameron, 2005). According to Cameron (2005), the USA has come to

realise the logical and cost effectiveness of decentralised options, and are now

implementing this in nearly half of their new wastewater developments.


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In general, a centralised approach creates an open cycle system that has many

sustainability downsides. This can include inefficient use of potable water supplies,

loss of freshwater resources and nutrients, pollution of the receiving water bodies and

the need for high energy infrastructure (Ho and Anda, 2004). Achieving wastewater

recycling of centrally collected wastewater can present a range of limitations such as,

the need for widespread transportation of the water to the desired location and the

potential inclusion of undesired contaminants such as heavy metals from industrial

wastewater (Cameron, 2005).

Economies of scale are often used as the underlying argument for the implementation

of centralised wastewater conveyance and treatment systems (Rule and Oliver, 1997).

While economies of scale do exist for the capital and operating cost of treatment

systems, there are diseconomies associated with the extensive piping system required

(Fane et al., 2002). A study by Clark (1997) found that there is little difference in

system life cycle cost between 500 and 1 million connections, and a slight

diseconomy above 10,000 connections.

Table 1 Factors affecting the decision to select a decentralised or centralised wastewater system (Ho, 2005, p16)

Economic Environmental Social Population density Protection of Environment Protection of public health

Location Conservation of resources: Convenience, security

Technology and its efficiency Energy Government policy

Investment Water and regulations

Operation and maintenance Nutrients Human settlement planning


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It is important to consider all sustainability factors (Table 1) when comparing

centralised and decentralised systems (Ho, 2005). While it is clear that decentralised

methods are more sustainable in terms of conservation of resources (i.e. water, energy

and nutrients), appropriate technology selection and operation and management

protocols are needed to ensure the other major sustainability factors are adhered to

(Anda, 1997).

The list of sustainability factors in Table 1 is also important to consider when

comparing different decentralised technologies. Of major consideration are factors

such as protection of the environment, operation and maintenance, investment,

protection of public health, and compliance with government policy and regulation.

2.2Domestic wastewater

2.21 Sources and streams

Domestic wastewater can also be termed ‘household’ or ‘sanitation’ wastewater,

and typically includes “…human wastes collected by either waterborne or non-

waterborne methods together with washwaters associated with kitchen,

bathroom and household laundry activities.” Gunn, 1997, p1 (See Figure 2,

below).


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Toilet Kitchen sink

Dish-

washerBath-

Shower

Clotheswasher

Misc.

Stormwater

Yellow water

Brown water

Blackwater

HOUSEHOLD

Greywater

Deepsewerage

Separate disposal

Figure 1 Various sources of household water including black, grey, brown and yellow, going to deep sewerage (diagram modified from IETC, 2002)

Domestic wastewater can be divided into a number of separate streams (IETC,

2002). The most common separation includes ‘blackwater’ from the toilet/s and

‘greywater’ from all other household sources (Figure 2). The blackwater can be

further divided into urine only ‘yellow water’ or faeces only ‘brown water’

(Huber, 2004).

Table 2 Comparison of the characteristics of untreated black, grey, yellow, and brown water (Source: Huber (2004) and DoH (2005)) Type of wastewater BOD Total

Nitrogen Total

Phosphorus Total coliforms

Untreated sewage (combined sources)

100-500 (mg/L)

~35 (mg/L)

~10 (mg/L)

107-109 (MPN*/100mL)

Blackwater 59% 97% 90% High Yellow water 12% 87% 50% Very low Brown water 47% 10% 40% Very high

Greywater 41% 3% 10% Medium * MPN – most probable number


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The different domestic wastewater streams have distinguishing water quality

characteristics; with blackwater mainly being higher in total coliforms and other

wastewater parameters (IETC, 2002) (Table 2). Once separated, the waste

streams can undergo treatment that is more suited to those effluents

characteristics (Huber, 2004). Kitchen water, which can often contain high

amounts of food particles, oils and grease (DoH, 2005), is sometimes included

as blackwater, depending on the designated outcomes of the separated sources

(IETC, 2002).

2.2.3 Nutrients

The main nutrient concerns include pollution and alteration of the environment by

nitrogen and phosphorus. Nitrogen is usually expressed as ammonium (NH4+) and

total nitrogen (TN); total nitrogen includes both particulate and dissolved nitrogen

(EPA, 1993). Dissolved nitrogen will include ammonium, nitrite and nitrate ions

(NH4+, NO2

- and NO3-), therefore ammonium is included in the TN. Phosphorus is

expressed as total phosphorus (TP) and includes both soluble (phosphate) and

particulate forms (Faust and Aly, 1998).

Ammonium is often singled out because it has more potential impacts to the receiving

environment. It can deplete dissolved oxygen (DO) levels, it is highly toxic to aquatic

animal life and it can cause a range of health effects to humans when consumed (EPA,

1993). Total nitrogen and phosphorus levels are important wastewater parameters

because they can cause eutrophication of receiving water bodies.


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Table 2 demonstrates the high amount of nutrients in the blackwater stream. The

yellow water stream contains a high percentage of the total nitrogen found in a

domestic wastewater stream, which is largely in the form of ammonium. Yellow

water also contains approximately 50% of the TP found in typical sewage and

separation of this water can drastically reduce the amount of nutrients in the

wastewater stream. The low pathogen levels means that it should be separated before

it comes into contact with the brown water, which is called no-mix separation. Once

separated the yellow water can be used as a fertiliser (Huber, 2004).

2.3 Wastewater treatment

The treatment of domestic wastewater is required before disposal or reuse can be

achieved. The level of treatment required depends on the end application of the

wastewater. Treatment can be described using three general processes, including

primary, secondary and advanced.

2.4.1 Primary

Primary treatment relies on physical processes to remove suspended solids, which will

include organic solids and reduce the BOD (EPHC, 2005). A common practice to

achieve primary treatment includes sedimentation (gravity settling of particulate

matter), although filtration using sand or other porous media can also be used (Asano,

1998). Primary treatment will typically remove particulate matter larger than about 50

micron (Asano, 1998), which often equates to roughly 50-70% of total suspended

solids and 25 – 40% of BOD (EPHC, 2005).


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2.4.2 Secondary

Secondary treatment refers to biological treatment using microbial activity and further

sedimentation, with the primary aim of removing BOD (EPHC, 2005). The digestion

of the organic matter can be achieved in anaerobic (without oxygen) or aerobic (with

oxygen) conditions, although aerobic processes are usually employed.

The micro-organisms are exposed to the wastewater either by suspended growth (in

situ) or attached growth (using media) systems, which allow for the metabolism of

solid and dissolved organic material (Gray, 1999). In aerobic digestion, the waste

organic materials are decomposed into CO2, H2O, and a few stable compounds and

some is utilised in the growth and reproduction of the organisms (Asano, 1998).

Secondary treatment processes will typically result in 85% BOD and SS removal and

some pathogen reduction (EPHC, 2005).

2.4.3 Advanced

Advanced (tertiary) treatment generally refers to a range of additional processes that

provide removal of colloidal and suspended solids, total dissolved solids, and other

specific constituents from secondary treated wastewater (Asano, 1998). There are a

range of processes available to achieve advanced treatment, although two types are

commonly used in domestic wastewater situations, discussed below.

Media filtration – achieves the removal of suspended particles larger than about 3

micron, which is likely to include the removal or nearly all bacteria and some viruses.

Water passes through the column of granular media and removes particulates via

impaction, interception, and physical straining. The removed substances accumulate


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in the filter media, which needs to be removed via backwashing and air scour (Asano,

1998).

Membrane filtration – includes the use of a permeable membrane. Methods include

microfiltration, ultrafiltration, nanofiltration, reverse osmosis and electrodialysis.

Microfiltration has similar removal characteristics of granular medium filtration.

Ultrafiltration will typically have a pore size of 0.1 micron (Asano, 1998), removing

all bacteria and some viruses. Reverse osmosis, nanofiltration, and electrodialysis will

remove a wide range of contaminants including dissolved ions (Cheremisinoff, 2002).

Backwashing is required to prevent fouling and scaling of the membrane (Asano,

1998).

2.4 Water management within the Perth Metropolitan Region

2.4.1 Water use

Perth is expanding rapidly in both population and geographical size, putting

increasing demands on the water supplies and centralised sewerage facilities (EPA,

2005). Currently, Perth residents use approximately 278GL (278 billion litres) per

year of high quality drinking water (WC, 2005). According to DoH (2005), of the

water supplied to domestic households on average over 50% is used for irrigation onto

gardens (Figure 1, below).


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Garden

watering

54%

Pool

2%

Bath/

shower

14%

Other 1%

Washing

machine

11%

Toilet

9%

Tap

7%

Leaks

2%

Figure 2 Average single residential household water usage in Perth (source: WC, 2005)

On top of the increasing water demand there has been a significant reduction in

rainfall over the past 30 years (Berti et al., 2004). A document released by the

Government of Western Australia in 2003 titled ‘A State Water Strategy for Western

Australia’, stated that there has been a 10-20% reduction in rainfall resulting in 40-

50% reduction in runoff to dams and reduced recharge of groundwater (GoWA,

2003). As a result of the increase in demand and lower rainfalls the eight storage dams

have been reduced to about 30% capacity (WC, 2005) and the city’s main supply of

ground water, the Gnangara Mound, is continually being depleted (EPA, 2005). In

awareness of this the state developed a water management strategy in 1994, detailing

the need for public awareness campaigns and garden watering restrictions (WRC,

2002).

2.4.2 Wastewater management

The PMR has large and extensive wastewater conveyance network consisting of over

9000km of pipe, stretching 30km east to west, and 120km north to south (WC, 2003).


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The system requires over 550 pump stations (WC, 2003) to distribute the sewage to 3

major treatment plants, including Woodman Point, Subiaco and Beenyup, as well as

several smaller plants (EPA, 2005). Currently only 3.3% (~3.4GL) of the total

wastewater is being recycled per year, with the remaining 100GL discharged via

ocean outfall (EPA, 2005). Due to the large and complex nature of this wastewater

conveyance network continual overflow events are evident. On average there are 11

wastewater overflow events per year in Perth, releasing volumes as high as 15 mega

litres (15 million litres) per spill (WC, 2003).

Table 3 The benefits and limitations of centralised sewerage networks in comparison to decentralised systems

Benefits Limitations Historically provided public health

benefits and a convenient household service.

Lower capital and operating cost of treatment systems due to economies of scale.

Easier management than can be supplied by one service provider.

Prevents nutrients and other contaminants entering superficial aquifers and wetlands within the Swan Coastal Plain

Currently conveys nutrients and other contaminants into the ocean where they can potentially pose less direct risk to public health and the environment.

The widespread network helps to remove onsite septic tanks systems that have associated environmental impacts

Many parts of the system rely on high levels of water use to provide adequate conveyance.

Diseconomies of scale present due to the need for large and extensive pipe work and deep excavations, especially with sandy nature of Swan Coastal Plain making deep excavation more difficult.

Energy intensive process just to achieve wastewater disposal (includes energy required for pumping and treatment)

Recycling of wastewater is difficult and costly due to distribution of reclaimed effluent requirements.

Combining of domestic and industrial wastewater makes recycling of effluent less desirable due to introduction of industrial contaminants.

A relatively fresh and treated wastewater stream is combined with saline ocean water.

Large raw sewerage spills are probable due to scale and complexity

Replacement of piping network costly and disruptive to public.

Potential environmental impacts associated with point source disposal into the ocean and spill events


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The major benefits and limitations of a centralised sewerage network within the Perth

Metropolitan Region are summarised in Table 3. While many sustainability issues

associated with the current approach have been identified, the WA government

currently believes the benefits outweigh the limitations. According to WAGov (1996),

this is largely based on the argument that it provides a convenient household service

and helps to remove onsite septic tank systems. However, as potable water supplies

are becoming less abundant the government is now realising the need to strongly

consider wastewater recycling, which is not easily achieved with a centralised sewer

network.

One potential method to achieve wastewater recycling in a way that will still provide

a convenient household service and remove the need for onsite systems can be found

with small community scale decentralised networks (White and Turner, 2003). These

systems service small residential communities, also called urban villages, by

combining the wastewater from many houses into one wastewater treatment plant

where it can then be recycled onto public parks and gardens, also known as public

open space. However, this presents a range of associated technical requirements to

ensure that suitable management systems are in place and public health and

environmental integrity is maintained (White and Turner, 2003).

2.4.3 Nutrient issues

A majority of the PMR is situated on the Swan Coastal Plain, which characteristically

consists of sandy soils that have a poor ability to retain nutrients. The PMR extends

east onto the Darling Plateau, which can contain deeply weathered soil profiles of

sandy/gravel surface layers underlain by iron rich zones and clays (Newsome, 1998).


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Due to the shallow water tables and sandy soils the surface waters located within the

PMR are susceptible to eutrophication by aberrant nutrient inflows (EPA, 2005). The

most likely recipients of nutrients leaching through the soil include the socially and

ecologically important Swan and Canning Rivers and their tributaries, as well as an

array of wetlands situated on the coastal plain (WC, 2003). As a result, nutrient

management is of key importance when considering irrigation of reclaimed domestic

wastewater.

2.4.4 Policies, Regulations and Standards

In 1981 the Western Australian government released its Sewerage Policy, which

states that “all properties within a sewered area be connected to the sewer network”

(GHD Pty Ltd, 2005, p15) unless special conditions exist (WAGov, 1996). The policy

was reviewed in 1990 to evaluate the possibility of decentralised sewerage systems in

urban developments, but concluded that the large scale centralised approach remains

the most reliable and environmentally acceptable means (WAGov, 1996).

The policy provisions that are currently in place present a major restriction on

implementing village scale wastewater recycling systems. However, the Western

Australian government has recognised the potential for greywater reuse, releasing the

Code of Practice for the Reuse of Greywater in Western Australia in January 2005

(DoH, 2005). There is also growing push from the scientific community and housing

developers to change the existing regulatory framework for wastewater, demonstrated

by the recent Water Corporation report prepared by GHD (GHD Pty Ltd, 2005).


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2.6 Summary

The PMR is a prime example whereby decentralised wastewater recycling needs

thorough consideration, as the city is rapidly growing, there are existing water supply

issues, and there is large irrigation demand. A statutory sewer connection requirement

does limit the wide scale application of decentralised wastewater recycling systems,

which is largely in place due to underlying concerns of environment and public health

protection. There is scope within the legislation for trial systems for investigation

purposes, of which wastewater recycling for irrigation of public open space in urban

villages is the most achievable method in the short to medium term due to less likely

public health risks.

Before the implementation of trial systems the regulatory authorities must first be

convinced that the technical requirements for reliable management systems and

improved protection of public health and the environment can be met. Therefore, the

technical requirements must first be identified to which the appropriate technologies

can be selected to meet those requirements. An essential part of selecting the most

appropriate technology is considering a range of sustainability factors, such as cost,

performance or efficiency. Overall, this process can be seen as a very intricate and

may potentially be limiting to the successful implementation of decentralised

wastewater recycling.


18

3. Project Objectives and Methods In response to Perth’s water supply concerns the Western Australian Government

implemented a State Water Strategy in February 2003. Part of this strategy was to

create a Premiers Water Foundation to support research and development projects that

investigate water conservation and reuse. A project titled “Demonstration of

Decentralised Wastewater Recycling in Urban Villages” was commissioned by the

foundation to achieve a number of demonstration projects and research studies. This

research study was commenced as part of the Premiers Water Foundation Project and

is focused towards investigation of the technical requirements of decentralised

wastewater recycling.

3.1 Aims and objectives

The specified research topic is: "Investigate decentralised wastewater recycling for

irrigation of Public Open Space (POS) in urban villages and determine technical

requirements for reliable management systems and improved protection of public

health and groundwater resources".

Therefore, the core purpose of this research project was to investigate the associated

technical elements of decentralised wastewater recycling to ensure that public health

and the environment are not jeopardised and a comprehensive management systems

can be developed. The identified technical requirements must be specific to

decentralised wastewater recycling onto public open space within urban villages of

the PMR.


19

As outlined in the introduction the findings from the investigation will be used to

develop a model that will assist the implementation of suitable decentralised

wastewater recycling systems. The model will aim to determine the associated

technical requirements and appropriate technologies, referred to as the technical

elements, to meet those requirements based on specified characteristics of the

situation. The developed model will therefore be titled the Decentralised Wastewater

Recycling for Public Open Space of Urban Villages Technical Elements Model or

‘Technical Elements Model’ for short.

3.1.1 Technical requirements

The technical requirements investigation involves identifying suitable parameters and

characteristics to meet the specified concerns. The major concerns have been

identified as being:

Public health protection

The major public health concern associated with domestic wastewater recycling is

exposure to pathogens during the recycling application, in this case POS irrgation.

Pathogens and other chemical contaminates may pose a threat to nearby water

supplies such as ground or surface water, which should also be considered.

Environmental protection

Environmental protection specifically relates to the protection of ground or surface

water bodies that are not directly used as a water source, and instead have important

environmental characteristics. Within the PMR the management of nutrients entering

the unconfined aquifers is a major concern due to the sandy nature of the soil profile.


20

Management systems

Appropriate management systems are an important part of ensuring the ongoing

performance of the wastewater recycling. It relates specifically to the processes

involved in operation and maintenance of the overall system and making sure that the

recycling system will continually comply with the environmental and public health

requirements.

3.1.2 Appropriate technology choice

In order to develop a model that is effective at assisting with the implementation of a

village scale wastewater recycling system, a correlation between the technical

requirements and the technologies available is needed. The model should identify

which wastewater recycling system configuration will be the most appropriate for the

given technical requirements. This is referred to as appropriate technology choice and

is used to ensure that economic, social, and environmental factors are considered. The

technology choice component of the model will determine the wastewater recycling

system configuration, and will include:

Scale of collection

Scale of collection refers to the size of the overall wastewater recycling system and is

directly related to the rated daily flow it is designed to receive. Scale of collection is

important when determining the system components as it will often have a bearing on

which technologies are the most appropriate. This is largely due to economies of scale

associated with capital and ongoing costs.


21

Recycling system components

The system components will indicate the arrangement of technologies that can be

used to meet the specified requirements. There are three general wastewater recycling

system components that need to considered, including:

Core treatment – the initial treatment system that will typically provide the

primary and secondary treatment;

Additional components – any additional systems and processes that provide

extra quality enhancement of the wastewater such as tertiary filters and

additives;

End application – which refers to the public open space irrigation method.

Evaluation system

In order to select which core wastewater treatment type is the most appropriate for a

given situation, an appraisal and comparison of each end category within the

technology type catalogue is required. For this a treatment type evaluation system was

employed.

Assessment evaluation systems are commonly used in the building industry to assess

and compare building materials (Szokolay, 2005). Such systems provide a rating by

means of simple numerical score (i.e. 1 to 5) that provide a qualitative or quantitative

guidance figure. The system will usually entail a simple 2-dimensional matrix,

including a list of comparable items (i.e. building materials such as clay bricks) and

the evaluation criteria (i.e. environmental ratings such as material recyclability).


22

3.2 Methods

As specified in Chapter 1, four key research processes were identified to achieve the

objectives of this project. Chapter 2 has already addressed the investigation of the

current water management situation within the PMR and the issues associated with

wastewater recycling. The methods used for each of the remaining research processes

are discussed.

3.2.1 Technical requirements

Identify and analyse the technical requirements for decentralised wastewater

recycling onto POS within urban villages of the PMR.

There are many existing studies and regulatory documents that examine and specify a

range of technical requirements for wastewater recycling systems. These documents

were analysed to determine the suitable requirements for reliable management

systems and protection of public health and the environment, with specific relation to

the PMR. The identified technical requirements were then summarised into a form

that could easily be integrated to the Technical Elements Model.

3.2.2 Appropriate technology choice

Identify and analyse a range of technologies to determine the most appropriate

wastewater recycling system components to meet the acknowledged technical

requirements.


23

An intensive literature review was carried out to identify a range of different

technologies used to achieve wastewater recycling. The literature included text books,

journal articles and information provided by product manufacturers, such as

information pamphlets and websites. The identified technologies were appropriately

grouped and analysed for their performance characteristics, including organic (BOD

and SS) removal, nutrient removal, energy use, management costs, capital cost, sludge

production and footprint.

3.2.3 Decision support tool model

Develop the findings into a model that will systematically determine the technical

requirements and appropriate technologies for a given situation.

All the desktop research information gathered will be used to form a model that will

assist with establishment of the technical requirements and appropriate technologies

needed to meet those requirements. The model will also layout the progression of

requirements within the system design phase to assist provide assistance with overall

implementation process.


24

4. Technical Requirements

The technical requirements that are applicable to recycling wastewater via public open

space irrigation within WA are identified and reviewed in this chapter. The aim of the

review is to summarise and simplify the findings so that they can be easily integrated

into the Technical Elements Model.

The technical requirements have been divided into three major sections including:

Public health protection

Environmental protection

Management systems

4.1 Public health protection

4.1.1 Sewage

According to the Draft National Guidelines for Water Recycling (DNGWR) there are

many constituents within sewage (combined blackwater and greywater) that pose a

risk to human health, including chemicals and pathogenic micro-organisms (EPHC

2005). In order to reduce the associated risks to tolerable levels, health based targets

are required that are consistent with a level of risk that is acceptable (EPHC 2005).

Using a risk assessment process the draft guideline has determined a range of health

based targets for the recycling of wastewater.

The health based targets specified in the DNGWR are consistent with the guidelines

adopted by Western Australia, which have been titled the ‘Fit for Purpose Guidelines


25

for Recycled Water’ (EPA, 2005). It lists five different classes of water (A+, A, B, C

and D) along with their associated water quality objectives, the treatment processes

required to obtain the class and the appropriate uses (EPA, 2005). The water quality

objectives are largely focused on microbiological parameters (The ‘Fit for Purpose

Guidelines for Recycled Water’ is provided in Appendix C). Chemical contaminants

are not specified in these guidelines.

The DGNWR has identified a range of chemicals that may pose a risk to public

health, including heavy metals, organic chemicals, pesticides and disinfection by-

products. A review of three separate wastewater recycling case studies found that

most of the problematic chemicals had a high rate of compliance with drinking water

guideline values and many were below limits of detection. Some of the more specific

chemicals analysed included polychlorinated biphenyls (PCB’s), polycyclic aromatic

hydrocarbons (PAH’s), phenol, toluene, benzene, and endocrine disrupters.

Following this chemical hazards investigation, the DGNWR states

“In properly designed and managed recycled water schemes, health impacts from

these chemicals should be minimal, because of the relatively low exposure.”

Therefore, the main health risk associated with recycled wastewater for irrigation is

associated with the microbial pathogens. According to the DGNWR, the

microorganisms of concern include Bacteria, Viruses, Protozoa and Helminths. The

Fit for Purpose Guidelines for Water Recycling (FPGWR) considers all four pathogen

types in the Class A+ and A recycled water quality objectives and only E.coli in

Classes B, C and D, which is a bacteria species commonly used as a pathogen

indicator (Appendix A).


26

Table 4 A summary of two classes within the Fit for Purpose Guidelines for Water Recycling that are applicable for wastewater recycling via POS irrigation Class Recycled Water Quality

Objectives Treatment Process Uses

A

< 10 E.coli org/100 mL Turbidity < 2 NTU6 < 10 / 5 mg/L BOD / SS pH 6 – 9 7 1 mg/L Cl2 residual (or equivalent disinfection) <10 E.coli per 100 mL; <1 helminth per litre; < 1 protozoa per 50 litres; < 1 virus per 50 litres.

Secondary

Filtration

Disinfection

Urban (non-potable): with uncontrolled public access

C

<1000 E.coli org/100

mL pH 6 – 9 7 < 20 / 30 mg/L BOD /

SS

Secondary +

pathogen reduction

Urban (non-potable): with controlled public access

Application of the FPGRW for public open space irrigation is summarised in Table 4,

which does not include Class B as it is not specified as being applicable for Urban

(non-potable) uses (Appendix A). However, the DNGWR study indicates that Class B

should be preferred over Class C, as it poses less public health risk. Also, it is likely

that secondary treatment combined with conventional disinfection, (e.g. chlorination,

UV, etc.) will produce Class B water, and Class C largely represents pathogen

reduction by die-off achieved by long detention times in lagoons or wetlands (i.e.

>30days for secondary treated water or >60days for primary treated effluent).

Treatment systems that require high hydraulic retention times to achieve pathogen

die-off are not likely to be suitable within urban villages of a metropolitan region such

as Perth, mainly due to high land area requirements and other aesthetic challenges.


27

Therefore, other methods that rely on much shorter hydraulic retention times are

required along with a form of disinfection, which according to the DNGWR is likely

to achieve an effluent that complies with Class B. While Class B is not directly

required by the Department of Health guidelines; achieving treated effluent of this

quality will present less risk to public health.

The applicable parts of the FPGWR can be combined with the additional information

provided in the DNGWR to produce a more informative description of the available

water quality classes (Table 5, below). This can act as a more informative framework

to be used in the overall model, while also complying with the Department of Health

specified guidelines.

Table 5 A revised version of the Fit for Purpose Guidelines including information from the Draft National Guidelines for Water Recycling and to be used in the technical elements model. Class Irrigation Use Treatment Process Disinfection

Objectives Likely Disinfection

Requirements

A

Urban (non-potable): with uncontrolled public access - Uncontrolled Spray Irrigation

Secondary +

Advanced filtrat’n +

Disinfection

< 10 E.coli org/100 mL

Chlorine residual ~ >60mg.min/L;

UV light ~ 100mJ/cm2;

Or equivalent

B/C

Urban (non-potable): with controlled public access - Drip irrigation; or - Controlled spray irrigation*

Secondary +

Disinfection

<100 E.coli per 100 mL preferable <1000 E.coli per 100 mL acceptable

Chlorine residual ~ >15mg.min/L; Or equivalent

*Includes a combination of the following: No public access during irrigation Exclusion periods (e.g. no use until 1-4 hours after irrigation) 25-30m buffer zones to nearest point of public access Spray drift control


28

4.1.2 Greywater

DNGWR has identified that the total number of thermotolerant coliforms in greywater

can be as low as 101 and as high as 107 per 100mL, large due to the variable nature of

greywater. While these figures are largely determined based on the presence of E.coli,

in general there is little data on the levels of specific pathogens in greywater (EPHC,

2005). However, an assumption can be made that there will be less pathogens

associated with greywater than general sewerage due to the exclusion of blackwater.

Analysis studies of greywater to obtain typical water quality values are often carried

out on single dwellings causing a high degree of variability. Variability is likely to be

much lower for village scale collection of greywater, however, even with a low

variability a study by Ottoson and Stenstrom (2003), concluded that the health risks

from public exposure to greywater that has undergone secondary treatment but not

disinfection is unacceptably high. Therefore, disinfection objectives still have to be

considered for this domestic wastewater type.

Table 6 A revised version of the Fit for Purpose Guidelines for Water Recycling for greywater to be used in the technical elements model. Equivalent

Class

Irrigation Use Treatment

Process

Disinfection Objectives

Likely Disinfection

Requirements

A

Urban (non-potable): Unrestricted access - Spray irrigation - Sub strata irrigation

Secondary +

Disinfection

< 10 E.coli org/100 mL

Chlorine residual ~ >15mg.min/L; Or equivalent

B/C

Urban (non-potable): Restricted access Sub surface irrigation.

Primary

(or secondary)

<100 E.coli per 100 mL preferable <1000 E.coli per 100 mL acceptable

None


29

The DoH has released a Code of Practice for the Reuse of Greywater in Western

Australia (CPRGWA) (DoH, 2005). Within this document it specifies the level of

treatment required based on the greywater reuse application, which closely correlates

with the ‘Fit for Purpose’ guidelines outlined in Table 4. The CPRGWA

specifications have been adapted into a format similar to Table 5 to provide a simple

representation (Table 6). Note that secondary treatment combined with disinfection is

enough to achieve Class A equivalent effluent, while Class B can be achieved using

no disinfection, however it is required to have restricted access by using sub-surface

(bellow ground) drip irrigation.

4.2 Environmental Protection

Setting environmental protection guidelines is often linked to the key objectives of the

Australia’s National Strategy for Ecological Sustainable Development, which are to

(EPHC, 2005):

Enhance individual and community well-being and welfare by following a

path of economic development that safeguards the welfare of future

generations;

Provide for equity within and between generations; and

Protect biological diversity and maintain essential ecological processes and

life-support systems.

Environmental guidelines are designed to minimise the adverse consequences of

water recycling to end points or receptors within the environment (EPHC, 2005). For

the recycling of domestic wastewater onto POS of urban villages of Perth, the

receptors of most concern are native vegetation, soil, groundwater and surface water

bodies.


30

4.2.1 Australia and New Zealand Standard 1547:2000

While this standard is designed for flows up to a maximum of 14000L/week (lot scale

systems – see section 5.1, below), the soil classification and recommended hydraulic

loadings for recycled water irrigation can be applied to all size systems. The ASNZS

1547 also details how to carry out a Site-and-soil evaluation to determine the soil

classifications and characteristics, which is further discussed in the management

section.

Table 7 The indicative drainage classes specified in the ASNZS 1547, and the new drainage classes adopted in the technical elements model.

Soil texture Indicative permeability

(m/day)

Design irrigation rate

(mm/week)

Indicative drainage class

New drainage

class Gravels and

sands >3.0 35 Rapidly drained

Sandy loams 1.4 – 3.0 35 Well drained

Well drained

Loams 0.5 – 1.5 28 Moderately well drained

Moderately drained

Clay loams 0.06 – 0.12 25 Imperfectly drained

Light clays 0.01 – 0.12 20 Poorly drained Medium to heavy clays

0.01 -0.06 15 Very poorly drained

Poorly drained

Six soil categories with a different indicative drainage class are provided in the

standard. These have been summarised into three basic groups including well drained,

moderately drained and poorly drained for the purpose of the technical elements

model (Table 7). While most of the soils within the PMR are likely to be sandy and in

the well drained class, Perth is spreading east into the darling scarp where deeply

weathered profiles exist (Newsome, 1998). Therefore, it is important to include

considerations for all soil types.


31

The three new drainage classes correlate with the design irrigation rates (DIR), which

can also be roughly correlated with the three basic soil types of sands, loams and

clays. It should be noted that the DIR provided are conservative figures that do not

consider the effluent quality and the climatic characteristics of Perth.

The Department of Health (2005) has specified a figure of 10mm/day for drip or spray

irrigation in sandy and sandy loam soils (well drained). Therefore, it has been

assumed that the conservative figures listed in the ASNZS 1547 can be doubled to

obtain the maximum daily DIR for wastewater that has been treated to a level

consistent with that specified for greywater and sewage in section 4.1 above (E.g.

Class A and B/C).

Table 8 The new maximum design irrigation rates for the technical elements model. Drainage class ASNZS 1547 Design

irrigation rate (mm/week)

New Max. Design irrigation rate

(mm/day) Well drained 35 10

Moderately drained 28 8 Poorly drained <25 <7

The estimated maximum design irrigation rates are provided in Table 8, however,

more accurate design irrigation rates should be determined based on a consideration

of chemical hazards such as nutrients in the wastewater and the receiving

environment, which is disused further in section 4.2.2 and 4.2.3. These figures should

be used as guidance for initial design purposes and reduced if required during a more

accurate environmental analysis.


32

4.2.2 Draft National Guidelines for Water Recycling

The following review of various environmental considerations listed in the DNGWR

will refer to the three new drainage classes in terms of potential risk. The listed risks

that include reference to different soil types were determined following a review of

the provided information and correlation with the newly determined drainage classes.

There are many potential constituents within recycled water that may cause adverse

effects to the receiving environment. However, it is the substances within recycled

wastewater that are consistently in damaging concentrations that are of major concern.

According to the EPHC (2005), there are seven chemicals that can cause key

environmental hazards, which are summarised in Table 9 (below). Additional to

chemical contaminants, hydraulic loading and salinity is also considered as an

environmental hazard.

Table 9 A list of key environmental hazards associated with domestic wastewater Chemical of hazard Environmental End Point Effect of Impact on the

Environment Boron Accumulation in soil Plant toxicity Chlorine disinfection residuals Plants

Surface waters Directly toxic to plants Toxic to aquatic biota

Nitrogen Soils Soils Surface water Groundwater

Nutrient imbalance and pest and disease in plants Eutrophication of soils and effects on terrestrial biota Eutrophication Contamination

Phosphorous Soils Surface waters

Eutrophication of soils and toxic effects on phosphorus sensitive terrestrial biota (Native plants) Eutrophication

Salinity Infrastructure Soils Soils Groundwater Surface water

Rising damp, corrosion, secondary salinity Plant stress due to osmotic affects of soil salinity May increase release of cadmium from soil Increase salinity Increase salinity

Chloride Plants

Toxicity to plants when sprayed on leaves


33

Soils Surface water

Plant toxicity via root uptake Toxicity to aquatic biota

Sodium Plants Soils Surface water

Toxicity to plants when sprayed on leaves Plant toxicity via root uptake Toxicity to aquatic biota

Hydraulic loading Soil Groundwater

Water logging of plants Soil salinity

Table 10 Environmental factors, hazards and effects that need to be considered when determining environmental risk.

Water sources Uses Receiving environments and major end points

Key hazards Major Effects

- Sewer mining - Village scale system (sewerage) - Village scale system (greywater)

Irrigation Plants Soil Water body - surface - Groundwater Biota (aquatic and terrestrial)

Boron Chloride residuals Nitrogen Phosphorous Salinity Chloride Sodium Hydraulic loading

Concentration Contamination Eutrophication Loss of Biodiversity Nutrient imbalance Salinity Sodicity Toxicity Water logging

In order to determine the risks associated with the key hazards identified a range of

specific factors need to be considered, which are summarised in Table 10 (above).

Based on the confines of this study to the Perth Metropolitan Region and POS

irrigation the factors, each hazard can be analysed for its environmental risk. The

following analysis of the chemical hazards uses sourced information from the

DNWRG (EPHC, 2005) or others where indicated..

Boron

The source of boron in wastewater typically comes from water softeners, cleaners and

detergents, largely in the form of sodium perborate. Concentrations of boron in

recycled water are unlikely to be high enough to cause direct toxicity to plants,

although an accumulation in the soil may cause health problems in the plant species.


34

Provided that the soil is well to moderately drained (i.e. not clay) this is unlikely

present a major threat. Boron is found naturally in most soils and as result

concentrations in marine ecosystems are well above the expected levels in treated

wastewater.

Environmental risk: Low risk to plants in well to moderate drained soils and moderate

risk in poorly drained soils such as clays. Contamination risk to ground and surface

water from irrigation is low.

Target criteria: 0.5mg/L

Chlorine residual

Chlorine is often added to the wastewater for pathogen disinfection purposes during

the treatment process. A residual level of chlorine is often required to reduce the

health risks associated with recycled water. For Class A water the guideline specifies

1mg/L to be sufficient.

Environmental risk: Studies suggest that <1mg/L chloramine or free chlorine should

present a low risk to plants. Concentrations above 1mg/L should also pose a low risk

unless crop species were highly sensitive. Concentrations approaching 5mg present a

moderate risk and detailed assessment of the plant species should be carried out.

Provided that the chlorine residual contained water is not directly discharged to a

surface water body toxicity risk is low.

Target criteria: 1mg/L

Hydraulic loading


35

Environmental hazards can be caused by excess hydraulic loading to the soil, which

can cause water logging, surface pooling, runoff and secondary salinity. The main

considerations to determine the risk and appropriate controls are soil type and

application rate.

Environmental risk: Low risk for well to moderately drained soils and moderate to

high risk for poorly drained soils. Site selection of the irrigation system can be used to

choose the most suitable locations. The application rates should be determined

accordingly, based on soil type, evapotranspiration rates and rainfall events.

Conservative DIR are provided in ASNZS 1457 and summarised in Table 7, and

estimated maximum DIR figures are provided in Table 8.

Target criteria: Delivery of correct water volumes and groundwater >2m in poorly

drained sites.

Nitrogen

Nitrogen is a nutrient required by most plants in a greater quantity than any other soil

nutrient. Nitrogen can be found in high concentrations in both sewage and greywater,

although higher levels are expected in sewage because of the inclusion of human urine

which contributes to a large percentage of nitrogen in domestic wastewater (see Table

2).

Nitrogen within recycled irrigation water acts as a plant fertiliser, similar to a

fertigation system, although it is important to ensure that excess nitrogen is not

applied to the environment due to potential hazards. Some nitrogen will be removed

by the wastewater treatment system and biological processes (i.e. aerobic treatment


36

units) can be designed to increase the level of biological nitrogen removal. Currently

there are no chemical additives or non-biological processes that can viably remove

inorganic nitrogen from a wastewater stream. Urine separation can be employed to

significantly lower nitrogen levels of the incoming wastewater stream.

Environmental risks: The largest risk associated with excess nitrogen application to

the environment is contamination of groundwater through leaching, and

eutrophication of surface water bodies through groundwater and surface water

inflows. On top of plant uptake, nitrogen can also be removed within the soil and

groundwater via denitrifying bacteria. Therefore site characteristics such as ability of

the soil to prevent leaching, depth to groundwater, and distance to receiving surface

water body can all influence the associated environmental risk. Moderate to high risks

include nutrient imbalances and increased susceptibility to pests and disease in plants.

Direct plant toxicity presents a low risk.

Target criteria: Excess nitrogen following plant demand does not exceed the

assimilative capacity of the receiving environment. This is discussed further in

sections 4.2.3 and 4.2.4 below.

Phosphorus

Similar to nitrogen, phosphorus is an important nutrient required for plant growth,

although the levels required are somewhat lower. The concentrations of phosphorus in

domestic wastewater will often be lower than the nitrogen concentrations (10mg/L

phosphorus compared with 50mg/L nitrogen). Phosphorus is less susceptible to

leaching than nitrogen due to the availably to react with soil constituents to form a

precipitate. The ability of a soil to remove phosphorous in this way is referred to as


37

phosphorus retention index (PRI), and generally soils with higher clay content have a

higher PRI.

Due its properties phosphorus will often be in low supplies in native sandy soils and

similarly be the limiting nutrient to algal growth within natural wetlands of similar

geology. Native plants have adapted to the low levels of phosphorus and may suffer a

toxic affect when exposed to high concentration. According to Donnely et al (1997),

an increase in nutrient concentrations does not immediately increase algal growth as

many other factors are involved, however it is evident that it will increase the risk of

an algal bloom.

Some phosphorus is removed from a wastewater stream during the treatment process

through biological uptake and suspended solid removal. Biological treatment

processes can be modified to increase biological phosphorus removal, or alternatively

a precipitant can be added to the process to reduce levels to less than 1mg/L. A

combination of the two could see concentrations as low as 0.1mg/L or less.

Environmental risk: The most significant environmental risk associated with

phosphorus in recycled irrigation water is eutrophication of receiving surface water

bodies. Similar to nitrogen, the more permeable a soil and the closer the groundwater

and receiving surface water body, the higher the risk. Toxicity presents a high to

moderate risk to sensitive native plants and a low risk to non-sensitive plants

Target criteria: Concentrations should be minimised in landscapes that do not

typically contain high levels of the phosphorus and have a low PRI.


38

Salinity

Total dissolved salts (TDS) within water can include a range of soluble compounds,

although sodium and chloride are the most important from an environmental point of

view. High concentrations of salt within the soil can cause toxic effects to plants and

release cadmium by displacement with chloride. Irrigation with water containing high

salt concentrations can cause a build up of salt within the soil due to evaporation and

evapotranspiration processes, which effectively removes the water and leaves the salt.

Salt levels can also build up in surface water bodies to the point where it becomes

toxic to the biota.

The concentration of TDS in wastewater is largely dependant on the salinity of the

original water supply. Some of the wastes entering the feed water will contribute to

the TDS of the treated effluent, such as detergents and urine. According to study

detailed in the DNGWR, treated effluent from 40 wastewater treatment plants had an

average TDS of 675mg/L, and a maximum value of 1224mg/L. As a guide, water for

drinking is generally considered acceptable with a TDS between 100 to 800 mg/L,

and less than 500mg/L is preferable (DNGWR, 2005).

Therefore, if the supply water has a TDS of less than 500mg/L (which is preferable

for scheme water) then it is likely that the TDS of the treated wastewater will be less

than 1000mg/L. However, if feed water has a high TDS (i.e. greater than 500mg/L)

than the reclaimed effluent may have TDS concentration greater than 1000mg/L,

which is likely to cause a higher risk.


39

Environmental risks: Recycled water with a TDS less than 1000mg/L is likely to

cause a low risk in well to moderately drained sites, provided that the irrigation water

is not applied in areas of shallow groundwater expression. Poorly drained soils will

have a moderate to high risk. Recycled water with a TDS greater than 1000mg/L is

likely to cause a moderate to high risk to plants, soil, and groundwater in all soil

types. The risk of cadmium release by the soil is significantly increased with

concentrations above 1000mg/L.

Target criteria: TDS <1000mg/L with well to moderately drained soils and

groundwater >2m.

Chloride and sodium

Chloride and sodium are the main constituents of TDS (salinity). In addition to their

salinity impacts they can cause toxic effects and nutrient imbalances in plants, toxicity

to aquatic biota and other soil related impacts. High concentrations of sodium can

cause soil sodicity in which the clay particles absorb the sodium ion, which causes the

soil to swell when wet and prevents further movement of water through the soil.

Environmental risk: The DNGWR study found that concentrations of chloride and

sodium in recycled water is typically 135 and 180 mg/L respectively, which mostly

come from household products such as detergents. Such concentrations have a high to

moderate risk of causing toxicity to the foliage of some plants when sprayed directly

onto the leaves. In poorly drained soils the risk of sodium and chloride toxicity to

plants, and the risk of soil sodiciy is moderate to high.

Target criteria: Encourage low sodium and chloride containing household products,

use tolerant plants species and irrigate in well drained soils were possible.


40

4.2.3 Minimum setback distances.

The area to be irrigated with treated wastewater should be setback from various items

to ensure environmental performance, which can also be termed buffering distance or

buffer zones. The Code of Practice for the Reuse of Greywater in Western Australia

stipulates a range of guideline distances for greywater irrigation. As the distances are

for greywater that has been treated to an equivalent class B/C or better (Table 6), it

can be assumed that these figures can also be applied to blackwater treated to a class

B/C or better. The distances set by the Code of Practice are summarised in Table 4.7

(below).

Table 11 The minimum setback distances or ‘buffer zones’ to be applied in the technical elements model.

Item Drip irrigation (m)

Spray irrigation (m)

Closed fence boundaries 0.3 0.5 Open boundaries (e.g. open fence or no fence)

0.5 1.2

Buildings 0.5 0.5 Paths, drives, carports, etc. 0.3 1.8 Sub-soil drains 3.0 3.0 Bores (private) 30 30 Public drinking water source * 100 100 Wetlands and water dependant ecosystems where the PRI is <5

100 100

* Includes Drinking Water Source Protection Areas

4.2.3 Water Quality Protection Notes

4.2.3.1 Irrigation Protection notes

In order to obtain the target criteria concentrations for nitrogen and phosphorus the

Water Quality Protection Notes – Irrigation with Nutrient Rich Wastewater released

by the Department of Environment were reviewed (DoE, 2004). The

recommendations of the document are summarised in Table 12 and 13 below.


41

Table 12 Vulnerability to eutrophication of downstream surface water bodies and vulnerability classes as specified by Department of Environment Water Quality Protection Notes

Characteristics of the irrigated soil

Vulnerability to eutrophication of

downstream surface waters

(within 1 kilometre)

Vulnerability Category e

Significant b A Coarse grained soils a e.g. sands, or gravels. Low c B

Significant b C Fine grained soils (PRI d above 10) e.g. loam, clays, peat-rich sediment Low c D Notes: a. Specific restrictions may apply where near-surface soil conditions are likely to lead to rapid water movement without achieving significant immobilisation of entrained contaminants (e.g. in karstic limestone, coarse gravels or fractured rock). b. Significant eutrophication risk applies to translucent inland waters, with nutrient leaching pressures from catchment land use resulting in occasional algal blooms; or where warm season dissolved inorganic nitrogen concentrations exceed 1 mg/L and filterable reactive phosphorus (ortho-phosphate) concentrations exceed 0.1 mg/L in the water body. c. Low eutrophication risk applies to highly coloured waters, those with rarely observed algal blooms (less than 5000 cells/mL), having low nutrient pressure from land use and those with warm season inorganic nitrogen concentrations of less than 0.5 mg/L and filterable reactive phosphorus less than 0.05 mg/L. d. PRI means Phosphorus Retention Index, a scientifically determined measure of the phosphorus holding capacity of soils between the ground surface and base of the vegetation root zone e. These vulnerability categories are applied to nutrient application rate recommendations in Table 13. Table 13 The maximum inorganic nitrogen and phosphorus for the vulnerability categories as specified by Department of Environment Water Quality Protection Notes

Maximum inorganic nitrogen (TN)

Maximum inorganic phosphorus (TP)

Vulnerability Category

Application rate (kilograms /

hectare / year)

Equivalent water concentration (mg/ litre) a

Application rate (kilograms /

hectare / year)

Equivalent water concentration (mg/ litre) a

A 140 9 10 0.6 B 180 11 20 1.2 C 300 19 50 3.1 D 480 30 120 7.5

Notes: a. The N and P concentrations are based on an average of 50 mm (500 kilolitres/ ha) of water applied per week for 32 weeks/year, and no additional nutrient addition to the land (including animal manure). For other irrigation regimes, equivalent water concentration rates should be calculated on a pro-rata basis. b. Application rates are based on quantities of plant-available N and P (as N as ammonia & nitrate, and P as ortho-phosphate) to promote healthy vegetation growth that are matched to the growth cycle of the irrigated plant species. For materials that require micro-biological decomposition to release plant-available nutrients (e.g. decay of green-waste), the local conditions will need to be factored into calculations (i,e. time, moisture, warmth, available oxygen and absence of toxins).

It should be noted that the figures provided in Table 13 are recommended nutrient

(nitrogen and phosphorus) application criteria in irrigated waters, based no additional

measures being taken to minimise contaminant leeching. The figures are based on

50mm per week application rate for 32 weeks of the year. Many large scale

wastewater irrigation systems will require irrigation for 52 weeks of the year, unless


42

an alternative system is devised such as lagoon storage or deep sewerage disposal

during wet periods.

Within the sandy coastal plain of Perth it is likely that any groundwater receiving

water body within 1 kilometre will be classified as a category A, or at best category B.

Therefore, in these situations high nutrient removal should be achieved followed by a

detailed assessment to identify the risks and determine if any additional preventative

measures are required. Such measures may include:

Buffer plantings to strip nutrients from groundwater before receiving water

body

Location of irrigation system to maximise distance to groundwater (vertically)

and water body (horizontally)

Shandying (mixing with other source) the water to reduce nutrient

concentrations

Minimising the application rate

Reducing major nutrient sources from influent such as urine separation.

Other important specifications included in the Water Quality Protection Note are:

Any irrigation sites proposed within 500 metres of a sensitive environmental

feature should be referred with supporting information addressing the

environmental risks

For loamy soils irrigation rates 3 to 5 mm/ hour are reasonable, while sandy

sites may accept up to 15 mm/ hour without run-off. Irrigated water should

always be applied evenly. The irrigated area should be allowed to dry out for


43

24 hours between applications during hot, dry weather; and for 3 to 7 days

during cool weather.

Irrigated areas should have a land slope of between 1 in 20 and 1 in 200 to

avoid either soil erosion or formation of boggy ground.

4.3 Management systems

Following the technical requirement establishment it is important to ensure a detailed

management system is in place to verify the recycling systems ongoing performance

and compliance with the identified technical requirements. If the system is not

meeting the specified requirements, the appropriate changes can be made reduce the

associated risks.

4.3.1 Risk management framework approach

A very comprehensive management approach for recycled water is provided in the

DNGWR report (EPHC, 2005). It involves a detailed framework for management of

recycled water quality that includes 12 interrelated elements. The framework has been

adapted from the Australian Drinking Water Guidelines model. Each element contains

a number of components with subsequent actions that should be carried out to meet

that component. A summary of the elements, components and actions are briefly

reviewed in the tables provided in Appendix B.

A document detailing the relevant information for each element of the framework

should be compiled as a management plan, which can be used as a document that can

be submitted to the Department of Health to aid with the wastewater treatment system

approval. The document will provide a comprehensive level of detail about the public


44

health and environmental considerations required and management systems to be

undertaken.


45

Figure 3 Elements of the framework for management of recycled water quality and use (EPHC, 2005)

4.2.3.2 Nutrient Irrigation Management Plan

As the nutrient levels in treated effluent can often be higher than those stipulated in

Tables 12 and 13 and irrigation periods can be required during winter, the Department

of Environment will often require a Nutrient Irrigation Management Plan (NIMP) for

village scale wastewater recycling systems (DoE, 2004). A NIMP will be required if

Element 11 Evaluation and

audit

Element 12 Review and continual

development

Element 1 Commitment to responsible use and management of recycled water

System analysis and management

Element 2 Assessment of the recycled water system

Element 3 Preventive measures for recycled water Manag’t

Element 4 Operational procedures and process control

Element 5 Verification of recycled water quality

Element 6 Incident and emergency response

Element 7 Employee awareness and training

Element 8 Community Involvem’t & awareness

Element 9 Research

and development

Element 10 Document’n

and reporting

Supporting requirements


46

the irrigation of land areas exceeding 5,000 square metres is required, and may be

required for lesser areas where the surrounding environment is sensitive to nutrient

contamination.

The information required to fulfil a NIMP is very extensive. Some of the details

required include:

A pre-development and post-development nutrient irrigation and management

program;

Contingency plans;

Detailed site and soil analysis;

Nutrient inputs and outputs from the site; and

Expected seasonal nutrient uptake by the plant species being irrigated.

4.4 System design and implementation process

As mentioned previously the Onsite Domestic Wastewater Management standard is

mainly focused towards onsite or ‘lot scale’ systems. However, some of the

recommendations for system design and the implementation process can be employed

to larger scale wastewater recycling systems. This includes details on four reports that

need to be lodged to the approval authority as well as an implementation process and

persons involved stages list.

4.3.2.1 Reports

ASNZS 1547 lists four reports that will need to be lodged to the approval authority

for an onsite wastewater management system include:

Site-and-soil evaluation


47

Design report

Installation and commissioning report

Maintenance report

These reports are also relevant for village scale water recycling system

implementation stages, which are detailed in section 4.3.2.2, below. The contents that

should be included in each report are detailed within the standard, including an

example of a site-and-soil evaluation report structure.

4.3.2.2 Implementation stages

A table provided in the standard details the essential implementation stages for an

unsewered subdivision proposal, which can be made to include decentralised village

scale wastewater recycling systems. A revised version of the standard’s table to

include village scale irrigation of public open space systems is provided in Table 14

(below)

Table 14 The five stages of a decentralised wastewater recycling implementation process (ASNZS 1547)

Implementation stage Implementation process Implemented by Feasibility study Site-and-soil evaluation to check

areas are suitable for subdivision Evaluating environmental effects

- Developer - Planner/surveyor - Site evaluator - Local government - Site evaluator - Environmental authority

Subdivision design Site-and-soil check Site-and-soil evaluation Lot size and layout design Design reporting

- Site evaluator - Site evaluator/soil assessor - Surveyor - Designer

System design Selecting and sizing irrigation system Determine capacity of wastewater treatment unit

- Designer - Local government - Designer - Local government

System installation Constructing and/or installing wastewater treatment unit and irrigation system

- Installer/contractor - Designer - Local government

System use Operation and maintenance - Contactor


48

Monitoring

- Local government - Maintenance certificate - inspector - Contactor - Local government - Maintenance certificate - inspector


49

5. Appropriate Technology Selection “Environmentally sound practices in wastewater and stormwater

management are practices that ensure that public health and

environmental quality are protected. A range of technologies exist that

can achieve this objective” (IETC, 2002 p65).

Technology choice can be viewed as the most fundamental part of

implementing a more sustainable wastewater management system. Selecting the

most appropriate sanitation system in the design stages will help to ensure the

best possible economic, social and environmental solution (IETC, 2002).

While appropriate choice is vital, there are a wide range of variable factors and

site conditions to be considered. On top of this there are many different

technology types with countless variations of which to choose from, all of

which can make the process of technology choice difficult and time consuming.

Before selection of the most suitable technologies, the characteristics of the

wastewater recycling system and the receiving environment must be established.

One of the most important environmental issues surrounding wastewater

recycling in contamination through excess nutrients. The characteristics of the

wastewater recycling system that need to be considered are:

General configuration;

Scale of collection; and

Recycling system components (appropriate technologies).


50

5.1 General configuration

The first step in the design of a wastewater recycling system is to identify the

general system configuration. One of the core considerations of the general

system configuration includes how the wastewater is to be reused, such as

irrigation, third pipe distribution or other. As this project is focussing on

irrigation of wastewater onto public open space in urban villages, this

component is already apparent. The type of vegetation and likely area of POS to

be irrigated should be considered at this stage.

This remains the selection of the wastewater type, of which there are three

possible wastewater type configurations for village scale wastewater recycling,

including:

Sewage recycling (independent of deep sewerage network)

Greywater recycling (with blackwater to deep sewerage)

Sewer mining (deep sewerage connection still required)

Selection of these wastewater types can sometimes be governed by legislation.

For example the Perth Metropolitan Sewerage Policy may specify that deep

sewerage connection is required if the infrastructure is available at the site, in

which case an investigation of sewer mining or greywater recycling can be

considered.

5.2 Scale of collection

The scale of collection is a major consideration for decentralised wastewater recycling

systems. Different wastewater treatment systems are suited to different wastewater

flows, therefore making it an important part of appropriate technology choice. Also,


51

the scale will alter the values of certain characteristics, for example capital or

management cost per connection. Three different scales of collection have been

identified as:

Lot (individual house);

Cluster (medium cluster of houses); and

Village (large residential developments).

Table 15 The three available scales of decentralised wastewater recycling Acceptable size

Typical size Scale of

collection (kL/day) No. homes

(connections) No.

Inhabitants (kL/day) No.

connections No.

Inhabitants Lot

1.8 1 1 - 10 1.8 1 1-10

Cluster

3.6-50 2-100 10-250 ~30 ~60 ~150

Village

50-1000 100-2000 250-5000 ~100 ~200 ~500

Table 15 identifies the progression used to define the three different scales. The

acceptable size figures are very broad and represent what is acceptable within each

scale. The typical size figures were estimated based on a range of case studies and

available treatment technology information. The typical figures were used to calculate

the capital and management cost variations between different scales of collection.

Table 16 The general concept behind the scale of collection selection model Indicated

wastewater collection size

Wastewater treatment scales

1 home Lot Less than 50kl/day

Cluster scale

More than 50kL/day

Village scale

The scale collection model is not as clear cut as Table 16 indicates. A

development may have a total wastewater flow of 100kL/day; however, due to


52

design layout or geographic features it may be preferable to implement two or

more cluster systems rather than one village system. Therefore this is

incorporated into the appropriate technology choice investigation. As lot scale

collection of the wastewater is not suitable for public open space irrigation, it

will not be considered in this investigation.

5.3 Recycling system components

Following an extensive review of the all the available wastewater treatment

technologies it was determined that aerobic treatment units (ATUs) were the

only available wastewater recycling technology group suitable for village or

cluster scale collection and recycling of domestic wastewater in urban areas.

This is explained in Table 17, below.

Table 17 The various wastewater treatment type groups and there appropriateness for village or cluster scale decentralised wastewater recycling in urban villages

Group Appropriate (yes or no)

Reasoning

1. Aerobic Treatment Units Yes - Employs biological treatment processes that are simple and have been applied successfully for nearly 100years. - Small footprint required - Can easily be designed to achieve good nutrient removal

2. Infiltration Trenches No - Generally only used for small scale applications - Has limited wastewater reuse

3. Composting Systems No - Generally only for small scale applications 4. Ponds and Wetlands No - High footprint (land requirement) and aesthetics is often

an issue in urban developments 5. Anaerobic Systems No - Used to harvest biogas for energy

- Not suitable for relatively diluted wastewater typical of urban domestic situations

6. Physico-chemical Systems No - Very small footprint but minimal ammonium oxidation and total nitrogen removal

7. Greywater Treatment Systems No - Generally only for small scale applications, otherwise similar to ATUs

Table 18 The groups, categories and subcategories of the cataloguing system (A description of each category and sub category is provided in Appendix C)

Group Category Subcategory 1.0 Aerobic Treatment Units 1.1 Suspended growth 1.1a Activated sludge (continuous aeration) 1.1b Activated sludge (intermittent aeration)


53

1.1c Membrane bioreactor 1.2 Attached growth (forced aeration) 1.2a Submerged (continuous aeration) 1.2b Submerged (intermittent aeration) 1.2c Fluidised bed 1.2d Moving bed bioreactor 1.3 Attached growth (passive aeration) 1.3a Percolating (Primary – septic) 1.3b Percolating (Primary – humus) 1.3c Rotating biological contactor

Within the ATU wastewater treatment group a number of categories and

subcategories were identified. An evaluation system was devised to determine

which of the subcategories or ‘end groups’ is the most appropriate (Section 5.4

below). Such systems will provide the core treatment in the overall recycling

system, therefore leaving the additional treatment components and end

application.

The three recycling system components include:

Core treatment – the initial treatment system that will typically provide the

primary and secondary treatment;

Additional treatment components– any additional systems and processes that

provides extra quality enhancement of the wastewater such as tertiary filters

and additives;

End application – which refers to the public open space irrigation method

5.4 Evaluation system

5.4.1 Method

In order to select which of the ATU subcategories or ‘end groups’ is the most

appropriate for a given situation, an appraisal and comparison system is required. For

this a treatment type evaluation system was employed, which incorporates a range of


54

measures that are commonly required in the establishment of a wastewater recycling

system. These were determined by assessing a number of case studies for the most

commonly considered treatment system characteristics and explained in Table 19

(below).

Table 19 A brief description and associated measurement values used in the evaluation scoring system (Appendix D)

Evaluation criteria

Description Measurement value

Organic Biological oxygen demand and suspended solids (mg/L) in the treatment system effluent.

BODmg/L / SSmg/L

Percentage ammonia removal by the treatment system

NH4 (% removal)

Percentage total nitrogen removal by the treatment system

TN (% removal)

Nutrient

Percentage total phosphorus removal by the treatment system

TP (% removal)

Energy use Kilowatt hours used per kilolitre of water treated

kWh/kL

Capital cost Capital cost ($AU.) per kilolitre per day rated treatment capacity

$/kL/day

Management cost Yearly management cost ($AU.) per inhabitant

$/inhab/year

Footprint Footprint (land area required) in m2 per inhabitant

m2/inhab

Sludge Liquid sludge required to be treated/disposed of per year in litres per inhabitant

L/inhab.year

The evaluation system comprises of a numbering matrix that provides a score between

zero and ten for a range of evaluation criteria (Table 20, below). Low scores are better

than high scores (i.e. the poorest score is 10). The scores are linked with estimated

real values for that criterion, illustrated in the scoring key of the evaluation system

spreadsheet (Table 20 and Appendix E).

Table 20 An example of the scoring sheet used for the treatment type: Activated Sludge (continuous aeration) on a cluster scale (Appendix E) Evaluation criteria Description Value Score

Organic impact BODmg/L / SSmg/L 20/20 5 Nutrient impact Ammonia (% removal) >80 5


55

Nitrogen (% removal) <60

Phosphorus (% removal) <35

Energy use kWh/kL 1.5 8 Capital cost $/kL.day 7,000 7

Management cost $/inhab/year 40-60 6 Footprint m2/inhab 0.12-0.25 4 Sludge Liquid sludge to be treated

(L/inhab/year) 2000 6

A score was allocated to each of the ATU end groups using a range of sourced

literature, case study results and objective opinion. Objective option was used in

situations where specific information could not be sourced. It involves a non-biased

analysis of the treatment process to produce an estimated score, which is largely based

on a comparison with similar treatment processes.

Table 20 provides an example of the scoring sheet used for each end category. This

scoring sheet along with the others can be found in Appendix E. For the organic and

nutrient criteria only one score is given, even though there is more than one

measurement value (Table 20). The score is obtained by fitting the estimated values to

the scoring key, which produces one score for the combined values (Appendix E).

The two criteria that relate to cost (management cost and capital cost) are general

estimations based on a range of figures obtained from product companies, case studies

and sourced literature. The cost values used in the scoring system have limited

accuracy because they can vary from individual suppliers and the exact number of

connections.

The cost values used for cluster and village applications are largely based on the

typical flows for that scale (Table 15). The general finding was that a 100kL/day


56

(approximately 500 inhabitants) aerobic treatment unit system (village scale) would

cost approximately $500,000 installed (not including the piping network for collection

or irrigation) and roughly $10-15,000/year in management costs. A 30kL/day

(approximately 150 inhabitants) system would cost approximately $200,000 (not

including the piping network for collection or irrigation) and roughly $7,000-

9,000/year in management costs.

The cost related scores are based on very general figures to provide a

comparison that indicates economies of scale. Obviously, as the flows decrease

from the typical values used to calculate scores the cost figures are likely to

increase slightly. The same is also true for the reverse.

As mentioned earlier, contamination of the receiving environment via nutrients

in the recycled wastewater is an important consideration for appropriate

technology selection. For the purpose of ATU end group comparison three

different nutrient risk situations were applied – high, medium and low, which

correlate with soil vulnerability categories provided in Section 4.2.3 (Table 12).

Table 21 The nutrient risk allocated to the four soil vulnerability categories (Table12). Nutrient risk Correlating Soil

category

High Category A and B

Medium Category C

Low Category D


57

5.4.2 Results

There were ten different ATU end groups identified and analysed using the evaluation

system (Table 19 and 20). These are abbreviated for the purpose of the following

discussions. The abbreviations include:

1.1a – Activated sludge (continuous aeration): AS(co)

1.1b – Activated sludge (intermittent aeration): AS(in)

1.1c – Membrane bioreactor: MBR

1.2a – Submerged aerated filter (continuous aeration): SAF(co)

1.2b – Submerged aerated filter (intermittent aeration): SAF(in)

1.2c – Fluidised bed: FB

1.2d – Moving bed bioreactor: MBBR

1.3a – Percolating filter (primary – septic): PF(se)

1.3b – Percolating filter (primary - humus): PF(hu)

1.3c – Rotating biological contactor: RBC

Table 22 The organic and nutrient impact evaluation scores for the different ATU treatment types (Note: lower values are best) 1.1a 1.1b 1.1c 1.2a 1.2b 1.2c 1.2d 1.3a 1.3b 1.3c

Organic 5 5 3 5 5 4 4 5 4 5

Nutrient 5 4 3 6 5 5 5 5 6 5

Each ATU treatment type had the same individual organic and nutrient

performance scores for cluster and village applications (Table 22). However, the

other evaluation criteria varied between different scales of application. As a

result, there are different recommended treatment types for cluster and village

applications.

Cluster:


58

As the scale of collection increases the organic and nutrient removal becomes less

decisive, because performance enhancing upgrades become more feasible due to

economies of scale. Improvements such as biological nutrient removal, phosphorus

precipitation, and advanced filtration can significantly reduce nutrient and organic

parameters of the effluent. Organic and nutrients are still a consideration however, as

the better the performance of the core treatment process, the less work that is required

by the additional components.

0

2

4

6

8

10

1.1a AS

(continuous)

1.1b AS

(intermittent)

1.1c MBR 1.2a SAF

(continuous)

1.2b SAF

(intermittent.)

1.2c Fluidised

Bed

1.2d Moving

bed bioreactor

1.3a

Percolating

(septic)

1.3b

Percolating

(humus)

Capital

Energy Use

Footprint

Figure 4 A comparison of the ATU treatment types available on a cluster scale. (Note: lower values areas are best).

Nine out of the possible ten ATU subcategories are available for cluster scale

application. The technology type 1.3b – percolating filter (humus) is the most

outstanding, with the lowest energy use and more importantly lower capital cost

(Figure 4). The capital cost is competitive with village scale systems. The footprint is

slightly higher than most other systems, but this is likely to be of lower significance

on a cluster scale application. In high or medium nutrient risk zones additional

nutrient removal features should be included. If 1.3b is not suitable then 1.2d –


59

MBBR is the next best followed by 1.2b – SAF (intermittent aeration), due to the low

footprint and energy use (Figure 4).

Table 23 The ATU treatment types selected for cluster scale application Note: the first treatment type listed in each section is the first recommendation, and so on)

End use Nutrient risk

(i.e. drip irrigation)

(i.e. spray irrigation)

High

1st - 1.3b *+ 2nd - 1.2d *+ 3rd - 1.2b *+

1st - 1.3b *+^ 2nd - 1.2d *+^ 3rd - 1.2b *+^

Medium

1st - 1.3 b* 2nd - 1.2d* 3rd - 1.2b*

1st - 1.3b*^ 2nd - 1.2d*^ 3rd - 1.2b*^

Low

1st - 1.3b 2nd - 1.2d 3rd - 1.2b

1st - 1.3b^ 2nd - 1.2d^ 3rd - 1.2b^

+Additional nitrogen removal components

*Additional phosphorus removal components ^ Additional advanced filtration components

Village:

0

2

4

6

8

10

1.1a AS

(continuous)

1.1b AS

(intermittent)

1.1c MBR 1.2b SAF

(intermittent.)

1.2c Fluidised

Bed

1.2d Moving

bed bioreactor

1.3a

Percolating

(septic)

1.3c Rotating

biological

contactor

Energy Use

Footprint

Sludge

Figure 5 A comparison of the ATU treatment types available on a cluster scale. (Note: lower values areas are best).


60

Eight out of the ten ATU subcategories are available for village scale application.

Energy use, footprint and sludge production are an important evaluation criteria as

they tend to become more significant for large scale systems. The five standout

technologies include 1.1c MBR, 1.2b SAF, 1.2b MBBR, 1.3a PF (septic) and 1.3c

RBC.

Table 24 The ATU treatment types selected for village scale application Note: the first treatment type listed in each section is the first recommendation, and so on)

End use Nutrient risk

(i.e. drip irrigation)

(i.e. spray irrigation)

High

1st - 1.2d*+ 2nd - 1.3c*+ 3rd - 1.2b*+

1st - 1.2d*+^ 2nd - 1.3c*+^ 3rd – 1.1c*+^

Medium

1st - 1.2d* 2nd - 1.3c* 3rd - 1.2b*

1st - 1.2d*^ 2nd - 1.3c*^ 3rd - 1.1c*^

Low

1st - 1.2d 2nd - 1.3c 3rd - 1.2b

1st - 1.2d^ 2nd - 1.3c^ 3rd - 1.1c^

+Additional nitrogen removal components *Additional phosphorus removal components ^ Additional Advanced filtration components

Based on a comparison of the evaluation scores it was determined that 1.3c RBC and

1.2d MBBR are the two best treatment types for village application. 1.2b SAF and

1.1c - MBR are included as a third option for situations where MBBR and RBC

technologies are not available. The MBBR was listed as the first option due to the

lower footprint, which is important in village scale applications, and the better organic

removal performance than RBC.


61

6. Technical Elements Model The technical requirements identified in Section 4 and appropriate technology

selection requirements discussed in Section 5 can be correlated to form the Technical

Elements Model to achieve the sustainable implementation of a decentralised

wastewater recycling system.

Figure 6 The two employment phases of decentralised wastewater recycling system.

Figure 6 illustrates where the Technical Elements Model and information provided

throughout this research project (Technical report 2) ties in with the employment of a

decentralised wastewater recycling system. The research carried out by Beth Strang

Preliminary investigation

Implementation Process

Legislative requirements and challenges

Urban water modelling

Aims and goals

System design

Technical elements

Government approval

Operation, maintenance and monitoring

PWF Technical Report 1

By Beth Strang and

John Hunt

PWF Technical Report 2

By Shaun Jamieson


62

and John Hunt (Technical Report 1) is closely related to the preliminary investigation

phase of system implementation, while this investigation is central to the

implementation process, which involves the actual system design.

The association between the five steps of the implementation process and the

technical elements is provided in Figure 7 (below), which is an overall illustration of

the Technical Elements Model. Within the models framework there are more detailed

interrelations between the public health and environmental requirements, which is

illustrated in Figures 8 and 9 (below).


63

Figure 7 The five steps of the implementation process and the interconnection with the technical elements

General System Configuration

Section 5.1

Implementation Process

1. Feasibility study

2. Subdivision design

3. System design

Management System/plan Section 4.3

4. System installation

5. System use

Scale of collection

Section 5.2

Public health requirements Section 4.1

Environment requirements Section 4.2

Appropriate technology selection Section 5.3 and 5.4

Government approval

Operation, maintenance and

monitoring

Implementation process steps Section 4.4

Operation / governance

model

Evaluation system


64

Figure 8 The environmental requirements component of the model

Figure 9 The public health requirements component of the model

End (irrigation) use Type of wastewater

Water quality class

Public health requirements

Appropriate technology selection

Management system

Section 4.3.1

Environmental requirements

Controlled or uncontrolled public access

Sewage or greywater Section 4.1

Design hydraulic loading

Section 4.2.1 Soil and groundwater

analysis Section 4.2.4

Downstream surface waters + buffer zones

Section 4.2.3

Environmental risk

Target criteria

Environmental requirements

NIMP (N + P) Section 4.3.2

Appropriate technology selection

Nutrients (N + P)

Other receiving environm’ts (i.e. biota)

Section 4.2.2

Section 4.2.2

Chemical hazards


65

7. Discussion

7.1 Significant findings

Chapter 4 and 5 identifies and reviews many of the technical elements required for the

implementation of wastewater recycling systems in urban villages of Perth. The large

number of different considerations within the technical requirements and technology

selection process, and the interrelated nature of these components, produces a very

intricate overall procedure.

Without the developed Technical Elements Model most urban developers could easily

see the whole process as being to intricate and overlook various elements. If a

decentralised wastewater recycling system was implemented without the

consideration for each of the elements identified, then it is likely that public health

and the environment may be jeopardised. This strengthens the argument for the

Technical Elements Model, as it lays out the requirements in a simple and organised

framework, including the implementation stage at which they should be considered.

7.1.1 Technical elements model

The technical elements model identified in Chapter 6 helps to organise the technical

elements into the implementation processes stages, and shows a general interrelation

between the two. Such an organised framework is likely to aid developers with the

implementation of this water saving approach by laying out what needs to be carried

out during the system design stages to develop a sustainable and reliable system and

to gain government approval. The model may also be useful for government

departments who are involved with the approval process.


66

Water quality classes are commonly used throughout Australia to specify the quality

of water required for various applications to protect public health. These are generally

based on detailed risk assessment process and supporting research. For the purpose of

the model the Fit for Purpose Guidelines were modified slightly to include

recommendations for both sewage and greywater. The public health requirements

system within the model presents a simple and clear relationship between the

wastewater type, the end irrigation use of the effluent and the level of treatment

required.

The environmental requirements are slightly more detailed than public health as there

are no general guidelines available. A range of different sources were used to achieve

the required information and develop an environmental requirements system for the

model. As Figure 8 demonstrates, a range of site specific characteristics are required

to determine the associated risk and target criteria for each chemical hazard. The

chemical hazards of major concern include the macro-nutrients – nitrogen and

phosphorus. A detailed assessment of the nutrients will be required in the form of

Nutrient and Irrigation Management Plan (NIMP) – which in future may be referred

to as a Site Wastewater Application Management Plan (SWAMP) by Department of

Environment and Conservation.

The public health and environmental requirement results can be correlated with the

scale of collection to determine the most appropriate technologies to be implemented

and overall system design. This is demonstrated with the findings and

recommendations in the Results Section of Chapter 5, which are discussed further in


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Section 7.2 (below). There is potential to develop a more complex interrelation

between the technical requirements and the treatment system design, for example

there could be more detail regarding the additional components selection and

irrigation system sizing based on required design loading rates.

Once the technical requirements and technology selections have been established, a

detailed management system can be developed. The management system has not been

expanded upon in Section 6 as the framework has already been determined using the

12 elements of the Draft National Guidelines for Water Recycling (Figure 3). Once

the management system has been clearly stated in a management plan, the system

design can be subject to Department of Health approval. The Nutrient Irrigation

Management Plan will be required to gain Department of Environment approval. The

management plans can then be used to ensure that ongoing operation, maintenance

and monitoring of the system is carried out by the appropriate parties.

7.1.2 Appropriate Technology Selection

Cluster scale:

On a cluster scale the nutrient and organic performance becomes slightly less of a

consideration compared with lot scale systems, as these characteristics can be

improved by the use of additional components and system upgrades. Biological

nitrogen and phosphorus removal can usually be incorporated into a system when

requested to the supplier, and additional components such as phosphorus precipitation

and advanced filtration can be included to enhance performance (Faust and Aly,

1998). While these modifications will cost more, the economies of scale make it much

more viable compared to an individual house situation.


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If ATUs are required on a cluster scale then cost becomes a major influential factor,

as economies of scale can mean that each connection would cost approximately

$2,000 more than a village scale system (based on average typical flow values). The

exception to this rule, however, can be found with treatment type 1.3b PF(h). The

application of this treatment type on a cluster scale is likely to be cost competitive

with village scale connection costs.

This finding is largely based on the analysis of the Biolytix product, which was

designed in Australia and has already been applied in a number of cluster scale

situations. The more competitive capital cost is likely to be based on the simplistic

and modular nature off the design and the incorporation of the humus filter. As

mentioned earlier, the humus filter does not rely on hydraulic retention time and the

treatment process is relatively instantaneous. This will mean the sizing of the system

will not have to account for variations in flow as much as the alternative ATU

treatment types available.

Village scale:

The Biolytix design is more suited to cluster situations and is not available for village

scale application in the tool. While it can provide treatment for flows up to

100kL/day, it is more suited to typical cluster flows (i.e. ~30kL/day). This is because

the economies of scale do not tend to reduce the capital cost per connection above

30kL/day (i.e. it will stay the same). While the end price is likely to be similar to

village scale systems (~$5000/connection), the management costs and footprint will

be higher. This relatively constant system cost above 30kL/day and higher footprint is


69

likely to be a result of the modular design, which incorporates the same sized units

and joins them together to meet the design flows.

The most suitable treatment technologies available for village scale applications

include the 1.2d – MBBR and 1.3c – RBC. The MBBR has a very small footprint that

is a result of the low hydraulic retention of the system. The attached growth media

used are very high in surface area resulting in a high contact of the attached growth

biological film with the wastewater (Forster, 2003). The media is also circulated

throughout the bioreactor by using coarse air bubbles, which also increases contact

with the wastewater (Forster, 2003). The RBC treatment type uses passive aeration of

the attached growth biofilm by rotating partly submerged large circular disks

perpendicular to the flow of water (Metcalf and Eddy, 2004). This process was

estimated to use less energy than the MBBR and other village scale treatment types

due to the passive aeration process and no recirculation requirement.

The 1.1c – MBR is listed as a third option for situations where a high quality (Class

A) effluent is required. While it does provide a low footprint option that incorporates

advanced filtration into the original unit design, the additional workload of the

membrane filtration will result in a higher energy use than the alternative of applying

membrane filtration as an addition component.

7.3 Further development

As this research project has identified, there are many technical requirements and

technology options all with interconnected associations in the design and

implementation of a decentralised wastewater recycling system. While the model


70

developed is relatively basic, it helps to ensure easier and more detailed planning and

design of an urban village scale decentralised wastewater recycling system. It does

this by clarifying the various interconnections and indicating the stages at which they

should be achieved, however, there is much scope to continue the framework into a

more detailed model or even algorithm process. This could be used to expand on some

of the more intricate relationships identified and perhaps develop a more automated

derivation process. However, this would require further detailed investigations of the

existing elements and other possible relationships, such as exact depth to the

groundwater and the likely nutrient removal during percolation through the soil

profile.

Such a tool would require much investigation and perhaps the inclusion of

information technology expertise to convert the model into an electronic (computer

software) format. The tool could be created in way to assist developers that wish to

adopt the decentralised wastewater recycling approach by unravelling the complex

interrelation of technical aspects associated with the implementation process.

The tool could include the following characteristics:

Include simple water modelling functions such as daily expected wastewater

flows for the village, which can be integrated into the technology selection

process;

Develop a means whereby a user can select a series of specific characteristics

that will match their particular situation;

Automatically correlate the site specific characteristics with the appropriate

technical requirements;


71

Determine the most appropriate wastewater recycling system configuration

and technologies available to meet all possible situations.

Develop a simple means of displaying the suitable technical element results.

Include a performance analysis component that will allow for the comparison

of different wastewater recycling system configurations, including economic

characteristics (i.e. sewerage and irrigation piping costs)


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8. Conclusion The incorporation of decentralised wastewater recycling systems on the ‘urban

village’ or ‘subdivision’ scale can play a major role in the move towards water

sensitive urban development. As well, this approach can potentially provide a range of

sustainable development benefits over conventional centralised sewerage systems.

However, the decentralised sewerage system is still a relatively new concept within

Australia and its application is uncommon, which can often be related to the required

design processes being unfamiliar, intricate and hard to approve.

Achieving wastewater recycling within urban villages requires much planning,

innovative design and ongoing operation and management, which together forms the

implementation process. Within the implementation process there are many technical

elements which need to be considered to achieve the most sustainable option and gain

government approval, which are related to public health and environmental protection

criteria, management plan development and appropriate technology selection.

By identifying each technical element, how they interconnect, and where they apply

within the various implementation process steps, improved protection of public health

and the environment and more reliable management systems will result. As well,

making the implementation process easier will encourage the employment of this

water saving and potentially more sustainable approach. It is likely that the developed

Technical Elements Model will help to achieve this, however, further development

and trials are required before any definite conclusions can be made about the real life

performance of such model.


73

References Anda, M. (1997). Technology Choice and Sustainable Development. Proceeding of the workshop on adopting, applying and operating environmentally sound technologies for domestic and industrial wastewater treatment for the wider Caribbean Region. UNEP International Environmental Technology Centre. Osaka/Shiga, 1998. Asano, T. (1998). Wastewater Reclamation and Reuse. Water Quality Management Library – Volume 10. Technomic Publishing Company. Lancaster, USA. Berti, M.L., Bari, M.A., Charles, S.P. and Hauck, E.J. (2004). Climate Change, Catchment Runoff and Risks to Water Supply in the South-West of Western Australia, Department of Environment, Government of Western Australia. Cameron, C. (2005). Centralised Verses Decentralised Sewage. Australian Water Association Water Journal, March 2005. Cheremisinoff, N.P. (2002). Handbook of Water and Wastewater Treatment Technologies. Butterworth Heinemann. Melbourne. Clark, R. (1997). Optimum scale for urban water systems. Report 5 in the water sustainability in urban areas series. Water Resources Group. Dept. of Environment and Natural Resources. SA. Department of Environment (DoE). (2004). Water Quality Protection Note – Irrigation with Nutrient-rich wastewater. Western Australia, Feburary 2004. Department of Health (DoH). (2005). Code of Practice for the Reuse of Greywater in Western Australia. Water Corporation, Department of Environment and Department of Health January 2005. Available at www.health.wa.gov.au. Environmental Protection Agency (EPA). (2005). Strategic Advice on Managed Aquifer Recharge using Treated Wastewater on the Swan Coastal Plain. Section 16(e) report and recommendations of the Environmental Protection Authority. Perth, Western Australia. Bulletin 1199, October 2005. Environmental Protection and Heritage Council (EPHC). (2005). Draft National Guidelines for Water Recycling – Managing Health and Environmental Risks. October, 2005. Fane, S.A., Ashbolt, N.J. and White, S.B. (2002). Decentralised urban water reuse: the implications of system scale for cost and pathogen risk. Water Science and technology. 46(6-7):281-8. Faust, S.D. and Aly, O.M. (1998). Chemistry of Water Treatment. 2nd Ed. Ann Arbor Press. Michigan.


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Forster, C. (2003). Wastewater Treatment and Technology. Thomas Telford Publishing. London. GHD Pty. Ltd. (2005). Water Corporation: Non-potable Water Use – Guidelines for developers and their consultants. September, 2005. Government of Western Australia (GoWA). (2003). A State Water Strategy for Western Australia. Perth, Western Australia. Gray, N. (1999). Water Technology – An Introduction fro Environmental Scientists and Engineers. Arnold. Sydney. Gunn, I. (1997). Achieving sustainable use of on-site domestic wastewater systems. UNEP Environmental Technology for Wastewater Management – Conference Papers. International Regional Conference, December 1997. Hellstrom, D. and Jonsson, L. (2005). Evaluation of small wastewater treatment systems. Water Science Technology: Small Water and Wastewater Treatment Systems V. 48 (11-12): 61-68. Ho, G. (2005). Technology for sustainability: the role of onsite, small, and community scale technology. Water Science Technology: Onsite Wastewater Treatment, Recycling and Small Water and Wastewater Systems. 51 (10): 29-38. Ho, G. and Anda, M. (2004). Centralised versus decentralised wastewater systems in an urban context: the sustainability dimension. Summary paper from the Leading Edge Conference on Sustainability in Water-Limited Environments 2004. Huber (2004). DeSa/R – Means to Achieving the Millennium Goal for Sanitation. DeSa/R-Synoposium Berching / Opf. 14th July 2004. International Environmental Technology Centre (IETC). (2002). Environmentally Sound Technologies for Wastewater and Stormwater Management – An International Source Book. Technical Publication Series [15]. IWA Publishing Osaka/Shiga, 2002.

Metcalf and Eddy. (2004). Wastewater Engineering – Treatment Disposal Reuse. Third edition, McGraw Hell international editions, Civil Engineering Series.

Newsome, D. (1998). Soils and Environmental Science. School of Environmental Science. Murdoch University. Rule, H., and Oliver, J. (1997). Neighbourhood Wastewater Treatment Plants are Cheaper: Fact or Fiction. UNEP Environmental Technology for Wastewater Management – Conference Papers. International Regional Conference, December 1997.


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Water and Rivers Commission (WRC). (2002). Draft State Water Conservation Strategy for Western Australia, Water and Rivers Commission and Office of Water Regulation. Perth, Australia. Water Corporation (WC). (2003). Wastewater Overflows in the Perth Metropolitan Area to June 2003. Water Corporation of Western Australia. Perth, Australia. Water Corporation (WC). (2005). Our water sources. www.watercorporation.com.au/dams/dams_storage.cfm?rootparent=ourwatersources. Accessed: 5-4-2005. Western Australian Government (WAGov). (1996). Government Sewage Policy. Perth Metropolitan Region, 1996. White, S. and Turner. A. (2003). The Role of Effluent Reuse In Sustainable Urban Water Systems: Untapped Opportunities. National Water Recycling in

Australia Conference, Brisbane, September 2003.


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Appendix A – Fit for Purpose Guidelines for Recycled Water

Class Recycled Water Quality

Objectives

Treatment Process Range of Uses

A+

Turbidity < 2 NTU6 < 10 / 5 mg/L BOD / SS pH 6 – 9 7 1 mg/L Cl2 residual

(or equivalent disinfection)

<1 E.coli per 100 mL; <1 helminth per litre; < 1 protozoa per 50 litres; < 1 virus per 50 litres. <2-10mg/L nitrogen

Secondary

Filtration

Disinfection

Advanced treatment

Indirect Potable Reuse Aquifer Recharge

A

< 10 E.coli org/100 mL Turbidity < 2 NTU6 < 10 / 5 mg/L BOD / SS pH 6 – 9 7 1 mg/L Cl2 residual (or equivalent disinfection)

<10 E.coli per 100 mL; <1 helminth per litre; < 1 protozoa per 50 litres; < 1 virus per 50 litres.

Secondary

Filtration

Disinfection

Urban (non-potable): with uncontrolled public access Agricultural: eg human food crops consumed raw Industrial: open systems with worker exposure potential

B

<100 E.coli org/100 mL pH 6 – 97 < 20 / 30 mg/L BOD / SS

Secondary +

pathogen reduction

Agricultural: eg dairy cattle grazing Industrial: eg washdown water

C

<1000 E.coli org/100 mL pH 6 – 97 < 20 / 30 mg/L BOD / SS

Secondary +

pathogen reduction

Urban (non-potable): with controlled public access Agricultural: eg human food crops cooked/processed, grazing/fodder for livestock Industrial: systems with no potential worker exposure

<10000 E.coli org/100 Agricultural: non-food


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D mL pH 6 – 97 < 20 / 30 mg/L BOD / SS

Secondary crops including instant turf, woodlots, flowers

* Table adapted from Victorian EPA guidelines 1. Unless otherwise noted, recommended quality limits apply to the recycled water at the point of discharge from the WWTP 2. Secondary Treatment processes include activated sludge processes, trickling filters, rotating biological contractors, and may include stabilization ponds. 3. Filtration means the passing of wastewater through natural undisturbed soils or filter media such as sand and/or anthracite, filter cloth, or the passing of wastewater through micro-filters or other membrane processes. 4. Disinfection means the destruction, inactivation, or removal or pathogenic microorganisms by chemical, physical, or biological means. 5. Advanced wastewater treatment processes include chemical clarification, carbon adsorption, reverse osmosis and other membrane processes, air stripping, ultrafiltration, and ion exchange. 6. Turbidity limit is a 24-hour median value measured pre-disinfection. The maximum value is five NTU. 7. pH range is 90th percentile. A higher upper pH limit for lagoon-based systems with algal growth may be appropriate, provided it will not be detrimental to receiving soils and disinfection efficacy is maintained. 8. Chlorine residual limit of greater than one milligram per litre after 30 minutes (or equivalent pathogen reduction level) is suggested where there is a significant risk of human contact or where recycled water will be within distribution systems for prolonged periods. 9. Helminth reduction is either detention in a pondage system for greater than or equal to 30 days, or by a DOH approved disinfection system (for example, sand or membrane filtration). 10. Where Class C or D is via treatment lagoons, although design limits of 20 milligrams per litre BOD and 30 milligrams per litre SS apply, only BOD is used for ongoing confirmation of plant performance. A correlation between process performance and BOD / filtered BOD should be established and in the event of an algal bloom, the filtered BOD should be less than 20 milligrams per litre.


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Appendix B – Management system elements explained (EPHC, 2005) Element 1: Commitment to responsible use and management of recycled water Component Action Notes Responsible use of recycled water

• Involve agencies with responsibilities and expertise in protection of public and environmental health • Ensure that design, management and regulation of recycled water schemes is undertaken by agencies and operators with sufficient expertise

e.g. Dept. of Health and Dept. of Environment

Regulatory and formal requirements

• Identify and document all relevant regulatory and formal requirements • Identify governance of recycled water schemes • Ensure responsibilities are understood and communicated to employees • Review requirements periodically to reflect any changes

Regulatory and formal requirements may include: • WA and local government legislation and regulations • Operating licences and agreements • Recycled water use agreements and contracts • Agreed levels of service • Memoranda of understanding • Industry standards and codes of practice.

Partnerships and engagement of stakeholders (including the public)

• Identify all agencies with responsibilities for water resources and use of recycled water; regularly update the list of relevant agencies • Establish partnerships with agencies or organisations as necessary or where this will support the effective management of recycled water schemes • Identify all stakeholders (including the public) affecting, or affected by, decisions or activities related to the use of recycled water. • Engage users of recycled water; ensure responsibilities are identified and understood • Develop appropriate mechanisms and documentation for stakeholder commitment and involvement

Examples of agencies that may be involved include: • Health and environment protection authorities • Catchment and water resource management agencies • Primary industry agencies • Local government and planning authorities • Non-government organisations • Community-based groups • Industry associations • Construction industry representatives. Private organisations or companies may include: • Operators of recycled water distribution systems • Owners or managers of apartment buildings • Maintenance contractors who service recycled water treatment systems, including on-site systems • End users of recycled water (eg residents, farmers, councils).


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Recycled water quality policy

• Develop a recycled water policy, endorsed by senior managers, to be implemented within an organisation or by participating agencies • Ensure that the policy is visible and is communicated, understood and implemented by employees and contractors

Example of policy for recycled water supplier is given in DNGWR (2005), pg 18.

Element 2: Assessment of the recycled system Component Action Notes Intended uses and source of recycled water

• Identify source of water • Identify intended uses and receiving environments, endpoints and effects • Consider inadvertent or unauthorised use

Explained in more detail in section in 4.2 Sources include sewage or greywater • Characteristics and proximity of receiving waters (surface water and groundwater) • Characteristics of soils at the point of application (ie receiving environments) • Site hydrology (groundwater, soil permeability, drainage) • The type of crops or plants to be irrigated (ie endpoints) • Application rates • On-site storages • Climatic conditions and evapotranspiration rates • Characteristics and proximity of sensitive or protected ecosystems • Quantities required, time of application, spatial variability of application across a district or catchment.

Recycled water system analysis

• Assemble pertinent information and document key characteristics of the recycled water system to be considered • Assemble a team with appropriate knowledge and expertise • Construct a flow diagram of the recycled water system from the source to the application or receiving environments


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• Periodically review the recycled water system analysis

Assessment of water quality data

• Assemble historical data about sewage, grey water or stormwater quality, as well as data from treatment plants and of recycled water supplied to users; identify gaps and assess reliability of data • Assess data (using tools such as control charts and trends analysis), to identify trends and potential problems

Hazard identification and risk assessment

• Define the approach to hazard identification and risk assessment, considering both public and ecological health • Periodically review and update the hazard identification and risk assessment to incorporate any changes • Identify and document hazards and hazardous events for each component of the recycled water system • Estimate the level of risk for each identified hazard or hazardous event • Consider inadvertent and unauthorised use or discharge • Determine significant risks and document priorities for risk management • Evaluate the major sources of uncertainty associated with each hazard and hazardous event and consider actions to reduce uncertainty

The guidelines provided in section 4.1 can be used as a guideline for public health risk management. Section 4.2 provides a general guideline for environmental health risk management. A preliminary risk assessment should still be carried to accurately identify the hazards and associated risks. If unique or special hazards are identified or if the proposed recycling scheme includes unique or special aspects (not detailed in section 4.1 or 4.2) – then a detailed risk assessment should be carried out as per the DNGWR (2005).

Element 3: Preventative measures for recycled water management Component Action Notes Preventative measures and multiple barriers

• Identify existing preventive measures system-wide for each significant hazard or hazardous event, and estimate the residual risk • Identify alternative or additional preventive measures that are required to ensure risks are reduced to acceptable levels • Document the preventive measures and strategies, addressing each significant risk

Examples of preventive measures for recycled water systems - Water source protection (i.e. what goes into the sewage or greywater) - Water treatment (i.e. primary, secondary, tertiary) - Storage/treatment (i.e. lagoons, wetlands, infiltration etc.) - Protection and maintenance (i.e. buffer zones) - Restrictions on distribution system (i.e. site selection)


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- Users of recycled water (i.e. cross connection controls)

Critical control points

• Assess preventive measures throughout the recycled water system to identify critical control points • Establish mechanisms for operational control • Document the critical control points, critical limits and target criteria

Critical control points require: - Operational parameters that can be measured. - Operational parameters that can be monitored frequently to reveal failures etc. - Procedures for corrective action For mechanisms for operational control consider: - Critical limits - Target criteria

Element 4: Operational procedures and process control Component Action Notes Operational procedures

• Identify procedures required for all processes and activities applied within the recycled water system • Document all procedures and compile into an operations manual

Operational monitoring

• Develop monitoring protocols for operational performance of the recycled water supply system, including the selection of operational parameters and criteria, and the routine analysis of results • Document monitoring protocols into an operational monitoring plan

Corrective action

• Establish and document procedures for corrective action to control excursions in operational parameters • Establish rapid communication systems to deal with unexpected events

Examples of process-control programs include: • Descriptions of all preventive measures and their functions • Documentation of effective operational procedures, including identification of responsibilities and authorities • Establishment of a monitoring protocol for operational performance, including selection of operational parameters such as target criterion and critical limits, and the routine review of data • Establishment of corrective actions to control excursions in operational parameters • Requirements for use and maintenance of suitable equipment • Requirements for use of approved materials and chemicals in contact with recycled water • Establishment of procedures for restricted end uses


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Equipment capability and maintenance

• Ensure that equipment performs adequately and provides sufficient flexibility and process control • Establish a program for regular inspection and maintenance of all equipment, including monitoring equipment

Materials and chemicals

• Ensure that only approved materials and chemicals are used • Establish documented procedures for evaluating chemicals, materials and suppliers

• Establishment of procedures for activities undertaken by users of recycled water at application sites (particularly when end-use preventive measures are relied on to minimise the risk to acceptable levels).

Element 5: Verification of recycled water quality and environmental sustainability Component Action Notes Recycled water quality monitoring

• Determine the characteristics to be monitored • Determine the points at which monitoring will be undertaken • Determine the frequency of monitoring

Key characteristics to be monitored for verification include: • Microbial indicator organisms • Salinity, sodicity, sodium, chloride, boron, chlorine disinfection residuals, nitrogen and phosphorus • Any health-related characteristic that can be reasonably expected to exceed the guideline value, even if occasionally • Any characteristic of relevance to end use or discharge of the recycled water, which can be reasonably expected to exceed the guideline value, even if occasionally.

Application site and receiving environment monitoring

• Determine the characteristics to be monitored and the points at which monitoring will be undertaken

Areas requiring monitoring could include: • Soil chemistry and physical properties (eg salinisation, dispersion, structural stability) • Plants, terrestrial and aquatic biota • Groundwater and surface water quality and quantity (levels) • Infrastructure • Air.


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Documentation and reliability

• Establish and document a sampling plan for each characteristic, including the location and frequency of sampling, ensuring that monitoring data is representative and reliable

Recycled water user satisfaction

• Establish a recycled water user complaint and response program, including appropriate training of employees

Short-term evaluation of results

• Establish procedures for the short-term review of monitoring data and recycled water user satisfaction • Develop reporting mechanisms internally, and externally, where required

Short-term performance evaluation involves reviewing monitoring data and recycled water user satisfaction to verify that: • The quality of water supplied to application or receiving environments conforms to established targets and meets user expectations • The quality of receiving environments complies with approval conditions.

Corrective action

• Establish and document procedures for corrective action in response to non-conformance or recycled water user feedback • Establish rapid communication systems to deal with unexpected events

Element 6: Management of incidents and emergencies Component Action Notes Communication

• Define communication protocols with the involvement of relevant agencies and prepare a contact list of key people, agencies and stakeholders • Develop a public and media communications strategy

Incident and emergency response protocols

• Define potential incidents and emergencies and document procedures and response plans with the involvement of relevant agencies • Train employees and regularly test emergency response plans • Investigate any incidents or emergencies and revise protocols as necessary

Potential hazards and events that can lead to emergency situations include: • Non-conformance with critical limits, guideline values and other requirements • Accidents that increase levels of contaminants or cause failure of treatment systems (eg spills in catchments, illegal discharges into collection systems, incorrect dosing of chemicals) • Equipment breakdown and mechanical failure • Prolonged power outages • Extreme weather events (eg flash flooding, cyclones)


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• Natural disasters (eg fire, earthquakes, lightning damage to electrical equipment) • Human actions (eg serious error, sabotage, strikes) • Outbreaks of illness leading to increased pathogen challenges on treatment systems • Cyanobacterial blooms in storages or waterways • Kills of fish or other aquatic life • Crops destroyed by irrigation with recycled water.

Element 7: Employee awareness and training Component Action Notes Employee awareness and involvement

• Develop mechanisms and communication procedures to increase employees’ awareness of and participation in recycled water quality management

End users should be made aware of the importance of end-use restriction barriers. As a minimum, all end users should be aware of: • Restrictions on use of recycled water • Management requirements that are essential to ensure the sustainable use of recycled water • Any practice that will threaten human or environmental health.

Employee training

• Ensure that employees, including contractors, maintain the appropriate experience and qualifications • Identify training needs and ensure resources are available to support training programs • Document training and maintain records of all employee training

Element 8: Community involvement and awareness


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Component Action Notes Recycled water user and community consultation

• Assess requirements for effective involvement of recycled water users and community • Develop a comprehensive strategy for consultation

Communication and education

• Develop an active two-way communication program to inform recycled water users and promote awareness of recycled water quality issues • Provide information on impacts of unauthorised use • Provide information on the benefits of recycled water use

Communication with the public is essential. Communication can help recycled water users to understand and contribute to decisions about services provided by a recycled water supply. A thorough understanding of the diversity of views held by individuals in the community is necessary to satisfy community expectations.

Element 9: Validation, research and development Component Action Notes Validation of processes

• Validate processes and procedures to ensure they control hazards effectively • Revalidate processes periodically or when variations in conditions occur

Design of equipment

• Validate the selection and design of new equipment and infrastructure to ensure continuing reliability

Investigative studies and research monitoring

• Establish programs to increase understanding of the recycled water supply system, and use this information to improve management of the recycled water supply system

Applied research and development could focus on areas such as: • Increasing understanding of sources and potential hazards • Investigating improvements, new processes, emerging water quality issues and new analytical methods • Validation of operational effectiveness of new products and processes • Increasing understanding of the relationship between public health and environmental outcomes and recycled water quality • Assessing quality of products grown using recycled water, in comparison with similar products grown using alternative sources of water • Improving measurements of potential exposures to recycled water (eg through aerosols, consumption of irrigated crops and irrigation of household gardens) • Improving assessments of potential impacts of recycled water on soils and other receiving environments


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• Assessing epidemiological effects of recycled water schemes • Community attitudes, behaviours and effectiveness of education programs on recycled water.

Element 10: Documentation and reporting Component Action Notes Management of documentation and records

• Document information pertinent to all aspects of recycled water quality management, and develop a document control system to ensure current versions are in use • Establish a records management system and ensure that employees are trained to fill out records • Periodically review documentation and revise as necessary

Reporting

• Establish procedures for effective internal and external reporting • Produce an annual report aimed at recycled water users, regulatory authorities and stakeholders

Documentation should: • Demonstrate that a systematic approach is established and is implemented effectively • Develop and protect the organisation’s knowledge base • Provide an accountability mechanism and tool • Facilitate reviews and audits by providing written evidence of the system • Establish due diligence and credibility.

Element 11: Evaluation and audit Component Action Notes Long-term evaluation of results

• Collect and evaluate long-term data to assess performance and identify problems • Document and report results

A systematic review of monitoring results over an extended period (typically the preceding 12 months or longer) is required to: • Assess overall performance against numerical guideline values, regulatory requirements or agreed levels of service • Identify emerging problems and trends • Assist in determining priorities for improving recycled water quality


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management.

Audit of recycled water quality management

• Establish processes for internal and external audits • Document and communicate audit results

External audits could be conducted on: • The management system • Operational activities • Recycled water quality performance • The effectiveness of incident and emergency response or other specific aspects of recycled water quality management • Environmental indicators and performance.

Element 12: Review and continual improvement Component Action Notes Review by senior managers

• Senior managers review the effectiveness of the management system and evaluate the need for change

In order to ensure continual improvement, the highest levels of the organisation(s) should review the effectiveness of the recycled water-quality management system and evaluate the need for change, by: • Reviewing reports from audits, recycled water quality performance, environmental performance and previous management reviews • Considering concerns of recycled water users, regulators and other stakeholders • Evaluating the suitability of the recycled water quality policy, objectives and preventive strategies in relation to changing internal and external conditions such as: – changes to legislation, expectations and requirements – changes in the activities of the organisation – advances in science and technology – outcomes of recycled water quality incidents and emergencies • Reporting and communication.


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Recycled water quality management improvement plan

• Develop a recycled water quality management improvement plan • Ensure that the plan is communicated and implemented, and that improvements are monitored for effectiveness

Improvement plans may encompass: • Capital works • Training • Enhanced operational procedures • Consultation programs • Research and development • Incident protocols • Communication and reporting.


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Appendix C – Treatment type descriptions Table 1: Group 1.0 – Aerobic treatment units Category Subcategory Description 1.1 Suspended growth The active biomass is suspended and mixed within

the bioreactor using forced aeration. Sludge (separated biomass) is returned to the secondary chamber to increase the mean sludge age.

1.1a Activated sludge (continuous aeration)

The bioreactor receives continuous aeration. Additional anoxic and anaerobic chambers are usually added to enhance nutrient removal.

1.1b Activated sludge (intermittent aeration)

Sludge (separated biomass) is returned to the primary chamber for anaerobic digestion. Aeration is intermittent to increase nutrient removal.

1.1c Membrane bioreactor

Suspended growth is used and membranes are employed to separate solids rather than a settling chamber, allowing for a higher loading rate and producing a high quality effluent.

1.2 Attached growth (forced aeration)

The active biomass is attached to support media or filters within a bioreactor. Forced aeration is used to provide oxygen using less energy than suspended growth.

1.2a Submerged aerated filter (continuous aeration)

Forced aeration is provided continuously.

1.2b Submerged aerated filter (intermittent aeration)

Forced aeration is provided intermittently to enhance nutrient removal. Less energy is required for aeration than continuous aeration.

1.2c Fluidised bed The wastewater is forced up through a bed or granular media. Air or sometimes pure oxygen is added to the system.

1.2d Moving bed bioreactor

A unique submerged media with a high surface area is used to support the biomass. The media has a specific density to achieve vertical circulation within the bioreactor using forced aeration.

1.3 Attached growth (passive aeration)

Oxygen is provided to the attached biofilm by exposure to the atmosphere.

1.3a Percolating Filter (primary – septic tank)

The wastewater is percolated down through a bed of media. A septic tank or settling chamber is used to achieve primary treatment. Partial or full recirculation is usually required.

1.3b Percolating Filter (Primary – humus filter)

The wastewater is percolated down through a bed of media. A humus filter is used to achieve primary treatment, removing more solids and allowing for finer bed of media. Partial or no recirculation is usually required.

1.2d Rotating biological contactor

Large circular disks are partially submerged in the wastewater. They are rotated perpendicular to the flow in and out of the solution to aerate the attached biomass.


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Appendix D – Evaluation criteria description Evaluation criteria Description

Organic impact

This includes the likely effluent quality in terms of BOD and SS.

Nutrient impact

This includes the likely effluent quality in terms nitrogen and phosphorus, which are the two nutrients of most concern.

Energy use

This refers to the amount of artificial energy input needed to complete the treatment process. It will in most situations refer to electricity requirement. The term ‘artificial energy’ is used to exclude any energy input from a direct natural source, such as gravity or heating from the sun.

Capital cost

Capital refers to the monetary cost of installing the complete treatment system and does not include additional costs associated with fluid conveyance pipe work.

Management cost

The cost of management and maintenance of the treatment system per year

Involvement

This includes the level of involvement and awareness that the individual home owner will be obligated to. A score of zero would associate with a deep sewerage home, where as a village scale treatment system would still require some awareness as to what is put down the drain. Composting systems generally have a high involvement.

Sludge The amount of waste sludge produced by the treatment system that will require further management (reuse/disposal)

Footprint The footprint is the total land area required by the treatment system. It does not include the area required for irrigation purposes.


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