Lagoon Design and Performance Presented by: Dwight HOUWELING, Ph.D. EnviroSim Associates,...

Lagoon Design and Performance

Presented by:

Dwight HOUWELING, Ph.D.EnviroSim Associates, Flamborough, ON

4-hour Seminar presented September 22nd, 2008at Environment Canada, Burlington, Ontario

2

Outline

1. Lagoon Performance

2. Biology

3. Lagoon Design

4. Operation and Sampling

3

Protecting Receiving Waters

Raw Sewage

Treated Effluent

Biomass

LAGOON PERFORMANCE

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Solids Separation

Trucked or piped in wastewater enters the lagoon

LAGOON PERFORMANCE

5

Solids Separation

Solubles Particulates

Wastewater components separate through sedimentation. Settleable solids sink to the bottom layer. Soluble and fine solids remain in the top layer.

LAGOON PERFORMANCE

6

Solids Separation

Solubles Particulates

Settling removes only removes a portion of the “pollution”

Particulates

Solubles and Fine

Particulates

LAGOON PERFORMANCE

7

Biological Activity

Bacteria consume soluble matter and fine particulates and then settle to bottom, which clears up water top layer

Particulates

Bacteria Consume

Solubles and Fine

Particulates

Bacteria Grow and Settle

LAGOON PERFORMANCE

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Treatment Performance

Good settling depends on: quiescent conditions (still waters), not

too much wind; Minimum depth of water above

sediment layer Good biological activity depends on:

Temperature, dissolved oxygen, other factors

LAGOON PERFORMANCE

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Treatment Performance

The biggest variable in operating lagoons in Canada is temperature change between winter and summer

Cold temperatures and ice cover will affect biology but not so much settling

LAGOON PERFORMANCE

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Winter Performance

Settling

ice

Settling is good in winter but biological activity slows down

Particulates

Solubles and Fine

Particulates

LittleBiological Activity

LAGOON PERFORMANCE

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Summer Performance

Settling

SignificantBiological Activity

Particulates

Bacteria Consume

Solubles and Fine

Particulates

Warm temperatures and sunlight allow good treatment in summer

LAGOON PERFORMANCE

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Summer Performance

Particulates

Algae

Growth of Algae is beneficial but can sometimes be excessive

LAGOON PERFORMANCE

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Summer Performance

Waterways choked with algae – while they are alive they provide beneficial oxygen but when they die they consume oxygen, which can lead to anaerobic conditions (no oxygen)

LAGOON PERFORMANCE

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Biological Activity

Biological activity is critical to the treatment performance of lagoon processes

Rate of activity is temperature dependant Bacteria do most of the work Type of biological activity depends on whether

oxygen is present (aerobic) or not (anaerobic) Aerobic activity is the most energy efficient for

life and leads to better pond performance

LAGOON BIOLOGY

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Lagoon is an ecosystem

Metcalf and Eddy, 1991

LAGOON BIOLOGY

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Components of interest

Suspended Solids (TSS)TSS includes human waste, pathogens,

nutrients, algae and other bacteria etc.Biochemical Oxygen Demand (BOD)

Organic Matter that depletes oxygenNutrients - EutrophicationToxicityPathogens

LAGOON BIOLOGY

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Treatment in Lagoons

What is the fate of each of the following: TSS, BOD, Ammonia, P, Pathogens?

LAGOON BIOLOGY

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Bacteria

Bacteria consume organic matter and nutrients

Algae are photosynthetic bacteria that produce oxygen

Bacteria work fastest with oxygen but can work without – which can lead to foul odours

LAGOON BIOLOGY

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Grazers

RotiferProtozoa filter the water and consume bacteria

LAGOON BIOLOGY

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Biological Activity: Big and Small

Bacteria 0.001 mm

Protozoa, Rotifers0.1 mm

Daphnia1 mm

Geese – 1 m

LAGOON BIOLOGY

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Biological activity : Oxygen

Bacteria biodegrade organic aerobically (with O2) or anaerobically (no O2)

Aerobic biodegradation is faster and produces no smells

Anaerobic biodegradation is slower and can produce foul smells

Bacteria can be strictly aerobic, strictly anaerobic or facultative (active in both conditions)

LAGOON BIOLOGY

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Biological Activity : Temperature

Bacteria are active at low temperatures (<5oC) as well as high (40oC)

Significant rates of biodegradation of wastewater occurs at temperatures >5oC

Growth slows with decreasing temperature

Net loss of bacteria when growth rate is lower than rate of (decay + predation + washout)

LAGOON BIOLOGY

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Biological Activity : Other Factors

pH – Measure of Acidity/AlkalinityToxicity – Cyanide, Heavy metals

(Copper, Chromium etc.) can inhibit growth of bacteria

Contact between bacteria, pollutants and O2 – if all the bacteria are in the bottom sediments and the O2 and pollutants are in the overlying water column then no biodegradation

LAGOON BIOLOGY

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Treatment Steps : Dilution

Sewage will be diluted in lagoon and undergo sedimentation

LAGOON BIOLOGY

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Treatment Steps : Settling

Solubles + Some Solids

Solids

Fate sewage components will depend on settleability

Interested in knowing what fractions of influent waste are soluble and particulate (solid) components

LAGOON BIOLOGY

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Treatment Steps : Biodegradability

AEROBIC REACTIONS

ANAEROBIC REACTIONS

Fate will depend on biodegradability

Most human waste will biodegrade eventually, but is it readily, slowly, very-slowly or impossibly slowly biodegradable?

Examples:ProteinsCarbohydratesToilet PaperWoodPlastic

LAGOON BIOLOGY

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Treatment Steps : Gas Transfer

Ammonia can be removed by volatilization but it depends on pH

Useful to know what pH is…

NH3NH+4 + H+

LAGOON BIOLOGY

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Total Influent COD

Biodegradable COD

Unbiodegradable COD

Soluble Readily Biodegradable

Particulate Slowly Biodegradable

Soluble Unbiodegradable

Particulate Unbiodegradable

Influent Fractions

COD (Chemical Oxygen Demand) is a measure of all the organic matter in a sample

LAGOON SAMPLING

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Suspended Solids (TSS)

Suspended solids cause turbidityRemoving suspended solids means

removal of BOD, pathogens, metals, and other componentsTurbidity used as criteria for safe drinking

waterSuspended solids can clog receiving

waters, block light penetration, muddy stream bottoms

LAGOON SAMPLING

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Suspended Solids (TSS)

Suspended solids block light penetration

Changing the environment of receiving waters

LAGOON SAMPLING

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Biochemical Oxygen Demand (BOD5)

BOD is a measurement of the amount of biodegradable organic matter

Typically a 5-day test (BOD5) Units are mg O2/L because we are interested

in knowing the amount of oxygen depleted after biodegradation of the organic matter

BOD discharge can be associated with a depletion in dissolved oxygen (DO) concentrations in receiving waters

Without DO, fish die + bad smells

LAGOON SAMPLING

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Biochemical Oxygen Demand (BOD5)

Case study – shows DO “sag” due to BOD discharge

http://www.oxscisoft.com/hermes/casestudies.htm

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Nutrients: N and P

Nitrogen (N) and especially phosphorus (P) are limiting elements for growth of algae in most Canadian lakes and rivers

Human waste contain N and PDetergents contain PLead to eutrophication of receiving

waters

LAGOON SAMPLING

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Nutrients: N and PChinese Lake choked with Algae

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Toxicity: Ammonia

Sewage can contain toxic componentsIn domestic wastewater the principle

source of toxicity is ammoniaIndustrial effluents and landfill leachates

can contain toxic elements including metals

A government study found that ammonia was the principle source of toxicity in the Saint-Lawrence river (SLV 2000)

LAGOON SAMPLING

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Toxicity: Ammonia

Toxicity of ammonia to fish is dependant on pH

Ammonia can interfere with disinfection of drinking water

LAGOON SAMPLING

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Toxicity: AmmoniaFish Kills

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Acute toxicity of Ammonia

Environment Canada, 2004

(To

tal

Am

mo

nia

Nit

rog

en)

LAGOON SAMPLING

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Seasonal Factors

TemperatureBiologyTurnover Ice Cover

SunlightPhotosynthesis affects pH and DOpH has an important effect on effluent

toxicity!!!

LAGOON SAMPLING

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Seasonal Factors

Jan Apr Jul Oct Jan0

2

4

6

8

10

12

14

16E

fflu

en

t a

mm

on

ia (

mg

N/L

)

Averages of 3-years of measurements effluent of 1st lagoon at Drummondville (2000-2003)

Snowmelt Dilution

Biological Activity

(nitrification)

LAGOON SAMPLING

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COD test

Readily Biodegradable

Slowly Biodegradable



+

Inorganic Suspended Solids

Chemical Oxygen Demand

LAGOON SAMPLING

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BOD5 test

Biochemical Oxygen Demand





+


LAGOON SAMPLING

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TSS test

Total Suspended Solids





+


LAGOON SAMPLING

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NH3 test

TotalAmmoniaNitrogen

Organic Nitrogen

(Particulate & Soluble)

Colorimetric analysis

LAGOON SAMPLING

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PO4 test

Colorimetric analysis

Phosphate

Organic Phosphorus

(Particulate & Soluble)

LAGOON SAMPLING

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E. coli

CFU/100 mL





+


Important to know because of effect on human health but not a large contributor to oxygen demand

LAGOON SAMPLING

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Case Study: Role of Algae

Particulates

Weekly Sewage

Load

LAGOON SAMPLING

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Sewage is added to lagoon and bacteria use the oxygen to degrade organic matter (COD) Oxygen is replenished by algae at the surface of the lagoon using energy from the sun Oxygen is initially depleted because bacteria use oxygen faster than algae can produce it

LAGOON SAMPLING

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Oxygen is depleted faster at night when algae cannot produced oxygen If lagoon is loaded heavily so that bacteria use oxygen faster than algae

can replenish it, oxygen will drop to zero and anaerobic conditions will exist, leading to odours

LAGOON SAMPLING

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Algae tend to increase the pH in the lagoon which favours volatile form of ammonia

NH4+ ↔ NH3 + H+

Ammonia exists in equilibrium between non-volatile (NH4+) and volatile

(NH3) forms. At neutral pH, the non-volatile form is dominant

LAGOON SAMPLING

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Types of Lagoons

FacultativeOxygen input from algae and wind is

significantOdours generated in bottom layer are

eliminated in overlying aerobic layer

LAGOON DESIGN

O2 O2

O2O2

O2

ANAEROBIC

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Types of Lagoons

AnaerobicOxygen input is relatively insignificant

(organic load is too high)

LAGOON DESIGN

ANAEROBIC

Odours

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Facultative Lagoon – Process Operation

Aerobic and Anaerobic Zones allow for varied biology

Water Column is aerobicSediments are anaerobicExchanges between Sediments and

Water Column can be significantRelease of soluble organic matter and

nutrients from sediments (Benthic Load)

LAGOON DESIGN

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Facultative Lagoon – Design Criteria

Low Organic Load Hydraulic Detention Time : several days Depth (shallow to maximize A:V) L:W ratio (Plug flow vs. Complete Mix) Freeboard Inlet and outlet size, placement, depth

(distribution boxes to avoid a jet) Clay or geomembrane lining to limit seepage

LAGOON DESIGN

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Anaerobic Lagoon – Process Operation

Deep to minimize the effect of oxygen transfer across the lagoon surface

Both Water Column and Sediments are anaerobic

Significant gas production leads to odour problems

Should be upstream of an aerobic process

LAGOON DESIGN

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Anaerobic Lagoon – Design Criteria

High Organic Load Hydraulic Detention Time Depth (deep) L:W ratio Freeboard Inlet and outlet size, placement, depth

(distribution boxes to avoid a jet) Clay or geomembrane lining to limit seepage

LAGOON DESIGN

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Methane Gas captureCalifornia Manure Lagoon

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Aerated – process operation

Supply of DO allows for biological activity in winter

Influent has heat input which may keep lagoon from freezing over

If rate of feed is low relative to volume, freeze over is likely

LAGOON DESIGN

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Aerated – Design Criteria

Similar to facultative lagoon except:Greater Depth is allowed because natural

surface aeration is not important to treatment

Energy for aeration can increase operation costs significantly

LAGOON DESIGN

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Drummondville, QC WWTP60 000 m3/dV/Q = 11 days per lagoonAeration intensity = 0.5 – 1.2 W/m3

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L’Assomption, QC Qdesign = 7700 m3/d

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Seasonal Discharge

If lagoon freezes over and no aeration, minimal biological activity and poor treatment

Seasonal discharge is a good option in these cases to avoid discharging poor quality water in winter

LAGOON DESIGN

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Seasonal Discharge – Design Criteria

Hydraulic Detention Time : several months Depth : deep lagoons are good for storage in

water but shallow lagoons favour aerobic activity in summer

Freeboard Inlet and outlet size, placement, depth are

important for controlling discharge Clay or geomembrane lining to limit seepage

LAGOON DESIGN

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Seasonal Factors

TemperatureBiologyTurnover Ice Cover

SunlightPhotosynthesis affects pH and DOpH affects volatility and toxicity of ammonia

LAGOON DESIGN

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Alberta Design Criteria

Unaerated sewage lagoons in Alberta have no effluent requirements

Design must include 2 or 4 anaerobic cells with 2-day retention time in each cell

1 facultative cell with a 2 month retention time 1 storage cell with a 12 month retention time Lagoons are to be drained between late spring

and fall and discharge period should not exceed 3 weeks. i.e. Discharged once per year

LAGOON DESIGN

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Alberta Design Criteria

Anaerobic cells are 3 m deep and designed for desludging.

Facultative cell are a maximum depth of 1.5 m Storage cell are a maximum depth of 3 m and

is intended to act as a facultative cell. Slope of cell walls is 3:1 Wastewater lagoons in Alberta must be lined

to control seepage

LAGOON DESIGN

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Desludging

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Sludge Accumulation Slows down

Solids accumulate in the lagoon sediments Rate of accumulation gradually slows due to

digestion

Sludge Accumulation in Lagoon

Volatile Solids (tons) VS (tons)

Jan-02Jan-01Jan-00Jan-99Jan-98

Vo

lati

le S

oli

ds

(M

etr

ic T

on

s)

2,000

1,800

1,600

1,400

1,200

1,000

800

600

400

200

0

Drummondville, QC WWTP

LAGOON DESIGN

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Typical Wastewater Lagoon Design in Alberta

LAGOON DESIGN

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Quebec Design Criteria

Facultative lagoons are designed based on loading rates of 22 to 12 kg BOD5/ha/d in northern regions.

In general, design is for only seasonal discharge: in spring and fall.

Discharge should not be less than 3 weeks after the ice-melt. Systems generally comprise 2 cells in series or in parallel. Discharge should allow at least 0.3 m of liquid in the lagoon

below which solids entrainment in the effluent can be significant. For systems with continuous discharge in summer, at least 3

cells are recommended which respect the loading rates recommended above.

LAGOON DESIGN

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As is the case for Alberta, operational requirements are specified rather than effluent requirements.

MENV guide suggests design gives effluent BOD5 of 20-40 mg/L and TSS of 20-100 mg/L (depending on presence of algae)

Data from installations in Quebec in 1990 had an average of 400 to 20 000 CFU/100 mL

Sampling at least once per month of continuous discharge, discharge must be made during allowed periods and beginning and end of discharge must be noted.

LAGOON DESIGN

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Discharge must be conducted in such a way as to limit solids entrainment and to limit erosion from the lagoon

Sludge must be removed before it reaches the bottom of the effluent weir

Geotechnical stability of the lagoon berm should be inspected visually (fissures, sloughing)

Need for lining to control seepage depends on conditions of site and potential impacts to drinking water supplies

LAGOON DESIGN

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Lagoon Design

Poor design can lead to problems:Poor effluent qualityFoul OdoursExcessive sludge accumulationUncontrolled dischargeUncontrolled seepage

LAGOON DESIGN

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Exfiltration Lagoons

Seepage through berm adds a third treatment mechanism:

1. Settling

2. Biodegradation

3. Filtering Rate of seepage from lagoon will

impact treatment performance significantly

LAGOON DESIGN

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Exfiltration Lagoons

“Most of the communities have a dumping lagoon that exfiltrates through the sand and gravel of a berm down a wetland slope anywhere from a few hundred metres to several kilometres long. The wetlands are lush and green with vegetation that thrives on the wastewater while helping to treat it. What we’re finding is that in smaller communities, such as Chesterfield Inlet or Whale Cove, it works very well. The water that reaches the ocean is of very high quality.”

-Brent Wootton, senior scientist with the Centre for Alternative Wastewater Treatment at Fleming College Daily Commercial News and Construction Record, May 9, 2008, Reed Construction Data, Markham, ON

LAGOON DESIGN

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Sewage Lagoon at Whale Cove, NU

wetland

Downstream wetland provides further treatment beyond the lagoon

LAGOON DESIGN

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Sewage Lagoon at Whale Cove, NU

Lagoon effluent follows topography to ocean

LAGOON DESIGN

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Exfiltration Lagoon Performance

Why wetlands do or do not work is a current topic of study. Important factors include:

Loading (kg BOD5/m2)TemperatureRate of Seepage over YearExfiltration or uncontrolled runoffRetention time in downstream wetlands

LAGOON DESIGN

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Exfiltration

LAGOON DESIGN

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Operation and Sampling

What do we sample for?

What do the tests tell us?

Sampling plan to characterize Lagoon Behaviour Impact on receiving waters.

LAGOON SAMPLING

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Mass Balances

Propose a sampling campaign to characterize the removal of COD, N, and P for the following lagoon system.

*Flow In = Flow Out + Accumulation

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Sludge Production

After 5 years, the seasonal discharge lagoon at Exampleville is 60% full of sludge. The seasonal discharge lagoon at Pleasanthamlet 100 km away is only 25% full after 10 years.

•How can this be?•What information would you need to investigate your assumptions?•Plan a sampling campaign to investigate your claims

After 10 years After only 5 years

Low TSS High TSS

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Ammonia discharge

Local residents notice a fish kill in the river two years in a row in early June. The munipality’s lagoon discharges continuously into a wetland 500 meters from the river.

•Could effluent from the lagoon be responsible for the fish kill?•Can you offer an explanation for the fish kill?•What information would you need to investigate your assumptions?•Plan a sampling campaign to investigate your claims

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Exfiltration into surrounding Wetlands

Lagoon Design and Performance Presented by: Dwight HOUWELING, Ph.D. EnviroSim Associates,...

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