LAND APPLICATION SYSTEMS. OUTLINE OF PRESENTATION 1.Types of Land Applications: Brief Overview. 2.Definitions: Basic Terminology 3.Subsurface, Shallow

LAND APPLICATION SYSTEMS

OUTLINE OF PRESENTATION

1. Types of Land Applications: Brief Overview.2. Definitions: Basic Terminology3. Subsurface, Shallow Systems: In Depth

a. Leachfieldsb. Mound Systemsc. Seepage Pits

4. Land Disposal Systems: In Depth Coveragea. Slow Rate (SR) Infiltration Systemsb. Rapid Infiltration (RI) Systemsc. Overland Flow Systemsd. Planning and designd. Comparison

DEFINITIONS

Effluent: Flow going out of or leaving a process.Influent: Flowing intoBOD: Biological oxidation demandTSS: Total suspended solidsTN: Total nitrogenTP: Total phosphorousFC: Fecal ColiformAWT: Advanced water treatment SAR: Soil absorption rateSR: Slow rateRI: Rapid infiltrationOF: Overland flow

Types of Land Application Systems: Three Basic Types

1. SUBSURFACE, SHALLOW AND DEEP SYSTEMS

Used in single dwellings and small clusters of dwellings

2. LAND DISPOSAL SYSTEMSUsed for pretreated municipal effluents

3. IRRIGATION AND LANDSCAPE USESUsed for final treatment and discharge of wastewater on vegetated plots

Types of Land Application Systems

• The greater the waste strength, the larger the system must be.

• This is true for all system types, and although each type of system introduces water into the soil differently, sizing for the system you choose is critical.

• At some point the soil will not accept any more wastewater, causing failure.

SUBSURFACE, SHALLOW SYSTEMS


• Used for single dwelling or small clusters of dwellings

• In California there’s about 1 million households currently being served by these systems


Three most common shallow subsurface systems:

1. Leachfields (a.k.a. Leaching Chambers)

2. Mound Systems

3. Seepage Pits

SUBSURFACE, SHALLOW SYSTEMS: LEACHFIELDS


• Used to dispose of previously treated effluents (usually originally treated by means of septic tank)


• Usually set of leaching chambers in trenches

• Connected to primary treatment system by a pipe

• Effluent is distributed into the soil


ADVANTAGES:

• Easy and economic to construct

• Soil in trenches not likely to be compacted

• Extended useful life: low intrusion on soil and silt

• Small footprint


DISADVANTAGES:

• Not well suited for soils with high percolation rates (e.g. sandy soils)

• Not well suited for soils with high groundwater levels



Item Minimum Distance, ft

Private Water Supply Well 100Public Water Supply Well 300Leak or Impoundment 50Stream or Open Ditch 25Property Lines 10Water Line Under Pressure 10Sewer Interceptor Drain 25Source: Schultheis, 1999

Setback distances from leaching chamer disposal areas

Setback distances:


Long-Term Acceptance Rate (gpd/ft./yr)Soil Type Natural Soil SaproliteSands 0.8 – 1.0 0.4 – 0.6Coarse Loams 0.6 – 0.8 0.1 – 0.4Fine Loams 0.3 – 0.6 -Clays 0.1 – 0.4 -

LEACHING CHAMBER LONG-TERM ACCEPTANCE RATE

Soil Acceptance Rate:


Estimated Cost of Leachfield*Description Cost ($)Construction costsingle family- if site is suitable 2000-5000single family- if site is inadequate >10000

Operation CostSeptic Cleaning 500-1500/cleaning*Factors effecting cost: soil type, price of land, site topography, groundwater level

Preliminary Cost Estimate:


The seat under the old oak tree in a leachfield at Brookmans Park

SUBSURFACE, SHALLOW SYSTEMS: MOUND SYSTEM

• Used to further treat pre-treated effluents

• Comprised of pressure-dose sand filters that lie above the ground

• Discharge directly to the soil



Suited for sites with restriction such as:

• Slow or fast permeability

• Shallow soil cover over creviced or porous bedrock

• Elevated water table




ADVANTAGES:• Accommodate sites that otherwise

are not suitable for in-ground or at-gate onsite disposal

• Do not discharge directly to surface water bodies

• Can be used in most climates• Little excavation required


Mound System

Advantages to the Mound Systems

DISADVANTAGES:• Relatively high construction costs• Mound location can affect surface drainage pattern• Require pumping/siphon systems• Aesthetically obtrusive• Seepages/Leakages can affect mount integrity



Parameter Value

Depth of high water table (permanent or seasonal) 10 in.Depth to crevice bedrock 2 ft.Depth to non-crevice bedrock 1 ft.Permeability of top 10 in. Moderately lowSite slope 25%Filled site Yesa

Over old system Yesb

Flood plains Noa Suitable according to soil criteria (texture, structure, consistence).b The area and backfill must be treated as fill because it is a disturbed site.Source: Converse and Tyler, 1990.

Recommended soil and site criteria for "Wisconsin" Mound System

Criteria for Design:


Item Cost

Construction CostsSeptic tank (1000 gallon concrete tank)

1,000

Dosing chamber (includes pump and controls)

2,000

Mound structure 6,000Total Construction Costs 9000

Non-Component CostsSite evaluation 500Permits 250Total Costs 9,750Annual O&M CostsLabor @$20/hr. 20 per yearPower @8 cents/kWh 35 per yearSeptic tank pumping 75 to 150

every 3 years

Capital Costs

Source: Ayres Associates, Inc., 1997

Typical Cost Estimate for a Single Home Mound System

Cost Estimate for Mound Systems:


Picture of a typical on-site mound system

SUBSURFACE, SHALLOW SYSTEMS: SEEPAGE PITS

• Used for disposal of treated wastewater effluents

• Brick, block, or precast chambers placed in deep excavations surrounded by gravel of crushed rocks

• Effluents enter the chamber where it’s contained until it seeps through the walls and goes into the excavation wall




ADVANTAGES:

•Easy to construct

•Requires little maintenance

•Able to treat on sites with inadequate land resources for a standard absorption field


DISADVANTAGES:

•Danger of groundwater contamination

•Effluent is concentrated at one point, rather than large area

•Small flow able to be treated


LAND DISPOSAL SYSTEMS

• Used to dispose of pretreated municipal effluents

• Not widely used due to large land requirements, exacerbated by code-required setbacks (often including buffer areas and fencing)

• Also used less frequently due to requirement of significant pretreatment before application


Three main land disposal systems used for pretreated municipal effluents:

1. Slow-Rate Systems (SR)

2. Rapid Infiltration Systems (RI)

3. Overland Flow (OF)


LAND DISPOSAL SYSTEMS: SLOW-RATE SYSTEMS

• The oldest and most widely used form of land treatment, requires largest land area compared to the other land disposal systems

• Used to further treat wastewater effluent via contact with the soil-vegetation system

• Used when stringent requirements are placed on nutrients, pathogens, metals, and organics

• Used in agricultural, turf (e.g., golf courses, parks), and forest systems


• SR type 1- chosen to maximize amount of water to the minimum area of land

• SR type 2- chosen to optimize hydraulic loading for irrigation purposes


• Intended for wastewater treatment and hydraulic loading

• Limited by the hydraulic capacity of soil (nitrogen removal ability, etc.)

• Vegetation covers usually include perennial grasses due to the high nitrogen uptake ability, long WW application season, and low maintenance

LAND DISPOSAL SYSTEMS: SLOW-RATE SYSTEMS: Type 1

• Primarily intended for providing water and nutrients to agricultural, turf, and forest system

• Can not be applied to products consumed by humans



Treatment Plant and Golf Coarse:

LAND DISPOSAL SYSTEMS: SLOW-RATE SYSTEMS:

Slow Rate Spray Irrigation:


Harvesting Forage:


Spray Irrigation in Forest:


Drip Irrigation:


b.) Recovery Pathways

Underdrains Wells

a.) Application Pathway

Applied Wastewater

Evapotranspiration

• Organics are removed mainly within the first 1 to 2 cm by biological oxidation, filtration, and adsorption

OXIDATION e.g.:

Organic matter + O2 + bacteria -----> new cells + CO2 + NO3- + H2O



• Particulate material is filtered through the soil matrix


Nitrogen is removed by:

• Vegetation uptake

• Biological denitrification

• Ammonia volatilization

• Retention within soil matrix




• Phosphorus removal via crop uptake and fixation processes in the soil matrix.


• SR Systems are very effective at removing harmful wastewater constituents

PARAMETER PERCENT REMOVALBOD 90 to 99+ percentTSS 90 to 99+ percentTN 50 to 90 percentTP 80 to 99+ percentFECAL COLIFORM 99.99+ percent

LAND DISPOSAL SYSTEMS: SLOW-RATE SYSTEMSADVANTAGES:

• Significantly reduced operational, labor, chemical, and energy requirements compared to conventional wastewater treatment systems.

• Economic return from the use and re-use of water and nutrients to provide marketable crops.

• Little or no disposal of effluent production.

• Recycling and reuse of water reduces water distribution and treatment costs for crop irrigation.

LAND DISPOSAL SYSTEMS: SLOW-RATE SYSTEMSDISADVANTAGES:

•Large land requirements

Specific problems associated with poor site selection include:

• Soil structure dispersion resulting from high dissolved salts concentration.

• Runoff and erosion for sites with steep slopes or lack of adequate erosion protection.

• Inadequate soil or groundwater characterization resulting in operational hydraulic problems.


Item RangeField Area 56 to 560 acres/MGD

Application Rate2 to 20 ft/yr

(0.5 to 4 in/wk)BOD Loading 0.2 to 5 lb/acre/d

Soil Depth at least 2 to 5 ftSoil Permeability 0.06 to 2.0 in/hr

Lower Temperature Limit 25 deg FApplication Method sprinkler or surface

Pretreatment Required preliminary & secondaryParticle Size

(for sprinkler applications)Solids less than 1/3

sprinkler nozzle

SR Design Criteria

Source: Crites, et al., 2000.

General design parameters for SR system:


Flowchart For The Design Of A Slow Rate System


A preliminary estimate of costs for planning purposes:

SR Estimated Costs*Construction Costs ($) O&M Costs ($/yr)

C = 3.187(Q)0.9331 C = 0.1120(Q)0.8176

C = 1.71(Q)0.999 C = 0.205(Q)0.5228

*Costs valid up to ~10 MGD.

Slow Rate, Sprinklers, Underdrain

Slow Rate, Sprinklers, Not Underdrained

C = costs in millions of dollarsQ = design flow, MGD

LAND DISPOSAL SYSTEMS: RAPID INFILTRATION

Usually used for:

• Ground water recharge

• Surface water recharge

• Recovery of renovated water (by wells or underdrains) for reuse

• Temporary storage of treated waters

NEED TO COVER THESE WORDS!

more



• Wastewater percolates through the soil and is treated through downward flow

• Vegetation is NOT a part of the treatment


Hydraulic pathways for RI systems:

a.) Hydraulic Pathway

Percolation

Evaporation

Applied Wastewater

Flooding Basins Recovered Water

b.) Recovery Pathways

Underdrains

c.) Natural Drainage Into Surface Waters

Flooding Basin


RI DESIGN CRITERIAItem

Basin Infiltration Area

Hydraulic Loading Rate

BOD Loading Soil Depth

Soil Permeability Wastewater Application Period Drying PeriodSoil Texture

Height of DikesApplication Method Pretreatment RequiredSource: Crites, et al., 2000.

Range

0.15 m (0.5 ft) above maximum expected water levelflooding or sprinklingprimary or secondary

0.4-4 ha (1-10 acres)Individual Basin Size (at least 2 basins in parallel)

0.3-5.5 ha/103m3/d (3-56 acres/MGD)

6-90 m/yr (20-300 ft/yr) [6-92 m3/m2/yr (150-2250 gal/ft2/yr)]

22-112 kg/ha/d (20 to 100 lb/acre/d)at least 3-4.5 m (10-15 ft)

at least 1.5 cm/hr (0.6 in/hr)4 hrs to 2 wks8 hrs to 4 wkscoarse sands, sandy, gravels

•Most RI failures are due to improper soil elevations.

• Soil depth, soil permeability, and depth to groundwater are the most important factors in site evaluation.


Removal rates are dependent on:

• Wastewater characteristics

• Soil characteristics

• Travel distance

• Climatic and seasonal variables


• BOD, Suspended Solids, and Fecal Coliforms are almost completely removed

• Nitrogen removal is about 50-99%

• Phosphorus removal is about 70-99%


Advantages:•Gravity distribution methods consume no energy.

• No chemicals are required.

• RI is a simple and economical treatment.

•The process is not constrained by seasonal changes.

• Effluent is of excellent quality.


Advantages:• The process is very reliable with sufficient resting periods.

• The process is suitable for small plants where operator expertise is limited.

• RI provides a means for groundwater recharge, controlling And then there

were threegroundwater levels, recovering renovated water for reuse or discharge to a particular surface water body, and temporary storage of renovated water in the aquifer.


Disadvantages:• Usually won’t meet nitrogen levels required

for drinking water aquifer discharge.

• Requires long term commitment of significant land area

• Requires annual removal of accumulated deposits of organic matter

• May require occasional removal and disposal of the top few inches of soil

• Clogging can occur when influent is received at high application rates from algal laden lagoons and ponds


• Flowchart For The Design Of A Rapid Infiltration System:


Estimating Costs for Rapid Infiltration Systems

(O&M includes the annual tillage of infiltration surfaces, and the repair of dikes, fences, and roads every 10 years.)

Cost Estimation Equations*

Construction ($)

C = 0.580(Q)0.888 C=0.054(Q)0.756

C = 0.597(Q)0.857 C=0.058(Q)0.756

C=0.683(Q)0.886 C=0.075(Q)0.641

Source: Crites, et al., 2000

C=Cost in millions of dollars; Q=wastewater flow in MGD

*Cost of preliminary treatment, monitoring wells, and transmission from preliminary treatment facilty not included.

Equations valid for up to 3785 m3/d (10 MGD) wastewater flow

Case I: RI w. no underdrains, no recovery wells

Case II: RI w. 50 ft deep recovery wells

Case III: RI w. underdrains

Operation and Maintenance ($)

LAND DISPOSAL SYSTEMS: OVERLAND FLOW SYSTEMS


• Used to achieve secondary treatment effluent quality when applying effluents comming from primary treatment facilities.

• High removal of Nitrogen, BOD, and Suspended Solids


• Applying of previously treated wastewater effluents to a vegetation-covered, graded land

• Applied via grated pipes or nozzles at top of slope or by sprinkler systems within the site



•Best suited for sites with relatively impermeable soils


Land Requirements:

• Low permeability soils

• Grading within 2-8%


Perennial grasses used for:

• Erosion control

• Slope stability

• Effluent treatment


Removal mechanisms for BOD and Suspended Solids:

• Biological Oxidation

• Sedimentation

• Filtration


Removal mechanisms for Nitrogen (typically removes 75-90%):

• Plant uptake

• Denitrification

• Ammonia Volatilization


Removal mechanisms for Phosphorus (typically removes 50-70%- can increase by addition of alum of ferric chloride prior to land application):

• Fixation processes in the soil matrix

• Crop uptake


• Effluent is collected in ditches and can be reused or discharged to a surface water body

• If discharged to surface body: NPDES permit required


• Flowchart For the Design Of Overland Flow Systems

LAND DISPOSAL SYSTEMS: COMPARISON


Comparison of site characteristics for land treatment processes (EPA, 1981).Slow Rate (SR) Rapid Infiltration (RI) Overland Flow (OF)

Grade <20% on cultivated land; <40% on noncultivated land

Not critical; excessive grades require much earthwork

Finish slopes 2-8%a

Soil permeability Moderately slow to moderately rapid

Rapid (sands, sandy loams)

Slow (clays, silts, and soils with impermeable barriers)

Depth to ground water 0.6-1m (minimum)b 1 m during flood cycleb, 1.5-3 m during drying cycle

Not criticalc

Climatic restriction Storage often needed for cold weather and during heavy precipitation

None (possibly modify operation in cold weather)

Storage usually needed for cold weather

aSteeper grades might be feasible at reduced hydraulic loadingsbUnderdrains can be used to maintain this level at sites with high ground water tablecImpact on ground water should be considered for more permeable soils

•Desirable characteristics, not rigorous standards:


•Terrestrial treatment units, design features, and performance (Reed et al, 1995):

Disposal System

Treatment Goals

Climate Needs Vegitation

Area* (ha)

Hydraulic Loading (m/y)

Effluent Characteristics (mg/L)

SRSecondary, or AWT

Warmer Seasons YES 23-280 0.5-6

BOD < 2 TSS < 2

TN < 31

TP < 0.1 FC = 0

RI

Secondary, or AWT, or Groundwater Recharge NONE NO 3-23 6-125

BOD < 5 TSS < 2

TN < 101

TP < 1 FC = 10

OFSecondary, N removal

Warmer Seasons YES 6-40 3-20

BOD < 10 TSS < 10

TN < 101

* For design flow of 3785 m3/d1Nitrogen (N) removal depends on type of crop and management

AWT = advanced water treatment, SR = slow rate, RI = rapid infiltration, OF = overland flow, BOD = biological oxygen demand, TSS = total suspended solids, TN = total N, TP = total phosphorus (P), FC = fecal coliforms, counts/100mL


Constituent Average Upper Range Average Upper Range Average Upper Range

BOD (mg/L) <2 <5 5 <10 10 <15SS (mg/L) <1 <5 2 <5 10 <20Ammonia as N (mg/L) <0.5 <2 0.5 <2 <4 <8TN (mg/L) 3e <8e 10 <20 5f <10f

TP (mg/L) <0.1 <0.3 1 <5 4 <6FC (#/100mL) ?? <10 10 <200 200 <2000

eConcentration depends on loading rate and cropfHigher values expected when operating through a moderately cold winter or when using secondary effluents at high rates.

aQuality expected with loading rates at the mid to low end of the application rangebPercolation of primary or secondary effluent through 1.5 m (5ft) of unsaturated soilcPercolation of primary or secondary effluent through 5.5 m (15ft) of unsaturated soil; P and FC removals increaseddTreating comminuted, screened wastewater using a slope length of 30-36m (100-120 ft).

Slow Rateb Rapid Infiltrationc Overland Flowd

Expected quality of treated water from land treatment processesa (EPA, 1991)

•Expected water quality: function of hydraulic loading, available soils for treatments, vegetation.



Documents

LAND APPLICATION SYSTEMS. OUTLINE OF PRESENTATION 1.Types of Land Applications: Brief Overview. 2.Definitions: Basic Terminology 3.Subsurface, Shallow