Transcript Lagoon Design and Performance

Lagoon Design and Performance
4-hour Seminar presented September 22nd, 2008
at Environment Canada, Burlington, Ontario
Presented by:
Dwight HOUWELING, Ph.D.
EnviroSim Associates, Flamborough, ON
Outline
2
1.
Lagoon Performance
2.
Biology
3.
Lagoon Design
4.
Operation and Sampling
Protecting Receiving Waters
Raw
Sewage
3
Biomass
Treated
Effluent
LAGOON PERFORMANCE
Solids Separation
Trucked or piped in
wastewater enters the
lagoon
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LAGOON PERFORMANCE
Solids Separation
Wastewater components separate through
sedimentation. Settleable solids sink to the bottom
layer. Soluble and fine solids remain in the top layer.
Solubles
5
Particulates
LAGOON PERFORMANCE
Solids Separation
Settling removes only removes a
portion of the “pollution”
Solubles and
Fine
Particulates
Solubles
Particulates
Particulates
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LAGOON PERFORMANCE
Biological Activity
Bacteria
Consume
Solubles and
Fine
Particulates
Bacteria consume soluble matter and
fine particulates and then settle to
bottom, which clears up water top
layer
Bacteria Grow and Settle
Particulates
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LAGOON PERFORMANCE
Treatment Performance

Good settling depends on:
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Good biological activity depends on:
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quiescent conditions (still waters), not
too much wind;
Minimum depth of water above
sediment layer
Temperature, dissolved oxygen, other
factors
LAGOON PERFORMANCE
Treatment Performance
9

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
Winter Performance
Settling is good in winter but biological
activity slows down
ice
Solubles and
Fine
Particulates
Little
Biological Activity
Settling
Particulates
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LAGOON PERFORMANCE
Summer Performance
Warm temperatures and sunlight allow good
treatment in summer
Significant
Biological Activity
Settling
Bacteria
Consume
Solubles and
Fine
Particulates
Particulates
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LAGOON PERFORMANCE
Summer Performance
Growth of Algae is beneficial but can
sometimes be excessive
Algae
Particulates
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LAGOON PERFORMANCE
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)
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LAGOON PERFORMANCE
Biological Activity
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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
Lagoon is an ecosystem
Metcalf and Eddy, 1991
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LAGOON BIOLOGY
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 oxygen
Nutrients - Eutrophication
 Toxicity
 Pathogens

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LAGOON BIOLOGY
Treatment in Lagoons
What is the fate of each of the following: TSS, BOD,
Ammonia, P, Pathogens?
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LAGOON BIOLOGY
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
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LAGOON BIOLOGY
Grazers
Protozoa filter the water
and consume bacteria
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Rotifer
LAGOON BIOLOGY
Biological Activity: Big and Small
Bacteria
0.001 mm
Protozoa, Rotifers
0.1 mm
Daphnia
1 mm
Geese – 1 m
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LAGOON BIOLOGY
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)

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LAGOON BIOLOGY
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)

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LAGOON BIOLOGY
Biological Activity : Other Factors
pH – Measure of Acidity/Alkalinity
 Toxicity – 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

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LAGOON BIOLOGY
Treatment Steps : Dilution

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Sewage will be diluted in lagoon
and undergo sedimentation
LAGOON BIOLOGY
Treatment Steps : Settling

Fate sewage components will depend
on settleability

Interested in knowing what fractions of
influent waste are soluble and particulate
(solid) components
Solubles + Some Solids
Solids
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LAGOON BIOLOGY
Treatment Steps : Biodegradability

Fate will depend on biodegradability

Most human waste will biodegrade
eventually, but is it readily, slowly,
very-slowly or impossibly slowly
biodegradable?
AEROBIC REACTIONS
ANAEROBIC REACTIONS
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Examples:
Proteins
Carbohydrates
Toilet Paper
Wood
Plastic
LAGOON BIOLOGY
Treatment Steps : Gas Transfer

Ammonia can be removed by
volatilization but it depends on pH

Useful to know what pH is…
NH+4
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NH3 + H+
LAGOON BIOLOGY
Influent Fractions
Total Influent
COD
Biodegradable
COD
Soluble Readily
Biodegradable
Particulate Slowly
Biodegradable
Unbiodegradable
COD
Soluble
Unbiodegradable
Particulate
Unbiodegradable
COD (Chemical Oxygen Demand) is a measure of
all the organic matter in a sample
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LAGOON SAMPLING
Suspended Solids (TSS)
Suspended solids cause turbidity
 Removing suspended solids means
removal of BOD, pathogens, metals, and
other components
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Turbidity used as criteria for safe drinking
water
Suspended solids can clog receiving
waters, block light penetration, muddy
stream bottoms
LAGOON SAMPLING
Suspended Solids (TSS)
Suspended
solids block
light penetration
 Changing the
environment of
receiving
waters

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LAGOON SAMPLING
Biochemical Oxygen Demand
(BOD5)
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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
Biochemical Oxygen Demand
(BOD5)
Case study – shows DO “sag” due to BOD discharge
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http://www.oxscisoft.com/hermes/casestudies.htm
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 P
 Detergents contain P
 Lead to eutrophication of receiving
waters

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LAGOON SAMPLING
Chinese Lake choked with Algae
Nutrients: N and P
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Toxicity: Ammonia
Sewage can contain toxic components
 In domestic wastewater the principle
source of toxicity is ammonia
 Industrial 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)

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LAGOON SAMPLING
Toxicity: Ammonia
Toxicity of ammonia to fish is dependant
on pH
 Ammonia can interfere with disinfection
of drinking water
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LAGOON SAMPLING
Fish Kills
Toxicity: Ammonia
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(Total Ammonia Nitrogen)
Acute toxicity of Ammonia
Environment Canada, 2004
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LAGOON SAMPLING
Seasonal Factors

Temperature
Biology
 Turnover
 Ice Cover
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Sunlight
Photosynthesis affects pH and DO
 pH has an important effect on effluent
toxicity!!!
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LAGOON SAMPLING
Seasonal Factors
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Effluent ammonia (mg N/L)
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Snowmelt
Dilution
Biological
Activity
(nitrification)
12
10
8
6
4
2
0
Jan
Apr
Jul
Oct
Jan
Averages of 3-years of measurements effluent of 1st lagoon at Drummondville (2000-2003)
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LAGOON SAMPLING
COD test
Readily Biodegradable
Slowly Biodegradable
Soluble Unbiodegradable
Particulate Unbiodegradable
Chemical
Oxygen
Demand
+
Inorganic Suspended Solids
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LAGOON SAMPLING
BOD5 test
Readily Biodegradable
Slowly Biodegradable
Soluble Unbiodegradable
Particulate Unbiodegradable
Biochemical
Oxygen
Demand
+
Inorganic Suspended Solids
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LAGOON SAMPLING
TSS test
Readily Biodegradable
Slowly Biodegradable
Soluble Unbiodegradable
Particulate Unbiodegradable
Total
Suspended
Solids
+
Inorganic Suspended Solids
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LAGOON SAMPLING
NH3 test
Colorimetric analysis
Total
Ammonia
Nitrogen
Organic
Nitrogen
(Particulate & Soluble)
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LAGOON SAMPLING
PO4 test
Colorimetric analysis
Phosphate
Organic
Phosphorus
(Particulate & Soluble)
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LAGOON SAMPLING
E. coli
Readily Biodegradable
Slowly Biodegradable
Soluble Unbiodegradable
Particulate Unbiodegradable
+
Inorganic Suspended Solids
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CFU/100 mL
Important to know because of
effect on human health but not a
large contributor to oxygen
demand
LAGOON SAMPLING
Case Study: Role of Algae
Weekly
Sewage
Load
Particulates
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LAGOON SAMPLING
Case Study: Role of Algae
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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
Case Study: Role of Algae
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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
Case Study: Role of Algae

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
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LAGOON SAMPLING
Types of Lagoons

Facultative
Oxygen input from algae and wind is
significant
 Odours generated in bottom layer are
eliminated in overlying aerobic layer

O2
O2
O2
O2
O2
ANAEROBIC
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LAGOON DESIGN
Types of Lagoons

Anaerobic

Oxygen input is relatively insignificant
(organic load is too high)
Odours
ANAEROBIC
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LAGOON DESIGN
Facultative Lagoon – Process
Operation
Aerobic and Anaerobic Zones allow for
varied biology
 Water Column is aerobic
 Sediments are anaerobic
 Exchanges between Sediments and
Water Column can be significant
 Release of soluble organic matter and
nutrients from sediments (Benthic Load)
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LAGOON DESIGN
Facultative Lagoon – Design Criteria
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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
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
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LAGOON DESIGN
Anaerobic Lagoon – Design Criteria
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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
Methane Gas capture
California 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
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LAGOON DESIGN
Aerated – Design Criteria

Similar to facultative lagoon except:
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Greater Depth is allowed because natural
surface aeration is not important to
treatment
Energy for aeration can increase
operation costs significantly
LAGOON DESIGN
Drummondville, QC WWTP
60 000 m3/d
V/Q = 11 days per lagoon
Aeration 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
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LAGOON DESIGN
Seasonal Discharge – Design
Criteria
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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
Seasonal Factors

Temperature
Biology
 Turnover
 Ice Cover


Sunlight
Photosynthesis affects pH and DO
 pH affects volatility and toxicity of ammonia
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LAGOON DESIGN
Alberta Design Criteria
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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
Alberta Design Criteria
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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
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
2,000
1,800
1,600
1,400
1,200
1,000
800
600
400
200
0
Jan-98
Jan-99
Jan-00
Volatile Solids (tons)
Jan-01
Jan-02
VS (tons)
Drummondville, QC WWTP
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LAGOON DESIGN
Typical Wastewater Lagoon Design
in Alberta
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LAGOON DESIGN
Quebec Design Criteria
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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
Quebec Design Criteria
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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
Quebec Design Criteria
72

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
Lagoon Design

Poor design can lead to problems:
Poor effluent quality
 Foul Odours
 Excessive sludge accumulation
 Uncontrolled discharge
 Uncontrolled seepage

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LAGOON DESIGN
Exfiltration Lagoons

Seepage through berm adds a third
treatment mechanism:
1.
2.
3.
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Settling
Biodegradation
Filtering
Rate of seepage from lagoon will
impact treatment performance
significantly
LAGOON DESIGN
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
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LAGOON DESIGN
Sewage Lagoon at Whale Cove, NU
Downstream wetland provides further treatment
beyond the lagoon
wetland
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LAGOON DESIGN
Sewage Lagoon at Whale Cove, NU
Lagoon effluent follows topography to ocean
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LAGOON DESIGN
Exfiltration Lagoon Performance
Why wetlands do or do not work is a
current topic of study. Important factors
include:
 Loading (kg BOD5/m2)
 Temperature
 Rate of Seepage over Year
 Exfiltration or uncontrolled runoff
 Retention time in downstream wetlands
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LAGOON DESIGN
Exfiltration
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LAGOON DESIGN
Operation and Sampling

What do we sample for?

What do the tests tell us?

Sampling plan to characterize

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Lagoon Behaviour
Impact on receiving waters.
LAGOON SAMPLING
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
81
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
High TSS
Low TSS
After 10 years
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After only 5 years
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
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