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Lagoon Design and Performance Presented by: Dwight HOUWELING, Ph.D. EnviroSim Associates, Flamborough, ON 4-hour Seminar presented September 22 nd, 2008.

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Presentation on theme: "Lagoon Design and Performance Presented by: Dwight HOUWELING, Ph.D. EnviroSim Associates, Flamborough, ON 4-hour Seminar presented September 22 nd, 2008."— Presentation transcript:

1 Lagoon Design and Performance Presented by: Dwight HOUWELING, Ph.D. EnviroSim Associates, Flamborough, ON 4-hour Seminar presented September 22 nd, 2008 at Environment Canada, Burlington, Ontario

2 2 Outline 1. Lagoon Performance 2. Biology 3. Lagoon Design 4. Operation and Sampling

3 3 Protecting Receiving Waters Raw Sewage Treated Effluent Biomass LAGOON PERFORMANCE

4 4 Solids Separation Trucked or piped in wastewater enters the lagoon LAGOON PERFORMANCE

5 5 Solids Separation SolublesParticulates Wastewater components separate through sedimentation. Settleable solids sink to the bottom layer. Soluble and fine solids remain in the top layer. LAGOON PERFORMANCE

6 6 Solids Separation SolublesParticulates Settling removes only removes a portion of the “pollution” Particulates Solubles and Fine Particulates LAGOON PERFORMANCE

7 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

8 8 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

9 9 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

10 10 Winter Performance Settling ice Settling is good in winter but biological activity slows down Particulates Solubles and Fine Particulates Little Biological Activity LAGOON PERFORMANCE

11 11 Summer Performance Settling Significant Biological Activity Particulates Bacteria Consume Solubles and Fine Particulates Warm temperatures and sunlight allow good treatment in summer LAGOON PERFORMANCE

12 12 Summer Performance Particulates Algae Growth of Algae is beneficial but can sometimes be excessive LAGOON PERFORMANCE

13 13 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

14 14 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

15 15 Lagoon is an ecosystem Metcalf and Eddy, 1991 LAGOON BIOLOGY

16 16 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 LAGOON BIOLOGY

17 17 Treatment in Lagoons What is the fate of each of the following: TSS, BOD, Ammonia, P, Pathogens? LAGOON BIOLOGY

18 18 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

19 19 Grazers Rotifer Protozoa filter the water and consume bacteria LAGOON BIOLOGY

20 20 Biological Activity: Big and Small Bacteria mm Protozoa, Rotifers 0.1 mm Daphnia 1 mm Geese – 1 m LAGOON BIOLOGY

21 21 Biological activity : Oxygen Bacteria biodegrade organic aerobically (with O 2 ) or anaerobically (no O 2 ) 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

22 22 Biological Activity : Temperature Bacteria are active at low temperatures (<5 o C) as well as high (40 o C) Significant rates of biodegradation of wastewater occurs at temperatures >5 o C Growth slows with decreasing temperature Net loss of bacteria when growth rate is lower than rate of (decay + predation + washout) LAGOON BIOLOGY

23 23 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 O 2 – if all the bacteria are in the bottom sediments and the O 2 and pollutants are in the overlying water column then no biodegradation LAGOON BIOLOGY

24 24 Treatment Steps : Dilution Sewage will be diluted in lagoon and undergo sedimentation LAGOON BIOLOGY

25 25 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

26 26 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: Proteins Carbohydrates Toilet Paper Wood Plastic LAGOON BIOLOGY

27 27 Treatment Steps : Gas Transfer Ammonia can be removed by volatilization but it depends on pH Useful to know what pH is… NH 3 NH H + LAGOON BIOLOGY

28 28 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

29 29 Suspended Solids (TSS) Suspended solids cause turbidity Removing suspended solids means removal of BOD, pathogens, metals, and other components Turbidity used as criteria for safe drinking water Suspended solids can clog receiving waters, block light penetration, muddy stream bottoms LAGOON SAMPLING

30 30 Suspended Solids (TSS) Suspended solids block light penetration Changing the environment of receiving waters LAGOON SAMPLING

31 31 Biochemical Oxygen Demand (BOD 5 ) BOD is a measurement of the amount of biodegradable organic matter Typically a 5-day test (BOD 5 ) Units are mg O 2 /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

32 32 Biochemical Oxygen Demand (BOD 5 ) Case study – shows DO “sag” due to BOD discharge

33 33 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 LAGOON SAMPLING

34 34 Nutrients: N and P Chinese Lake choked with Algae

35 35 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) LAGOON SAMPLING

36 36 Toxicity: Ammonia Toxicity of ammonia to fish is dependant on pH Ammonia can interfere with disinfection of drinking water LAGOON SAMPLING

37 37 Toxicity: Ammonia Fish Kills

38 38 Acute toxicity of Ammonia Environment Canada, 2004 (Total Ammonia Nitrogen) LAGOON SAMPLING

39 39 Seasonal Factors Temperature Biology Turnover Ice Cover Sunlight Photosynthesis affects pH and DO pH has an important effect on effluent toxicity!!! LAGOON SAMPLING

40 40 Seasonal Factors Averages of 3-years of measurements effluent of 1 st lagoon at Drummondville ( ) Snowmelt Dilution Biological Activity (nitrification) LAGOON SAMPLING

41 41 COD test Chemical Oxygen Demand LAGOON SAMPLING

42 42 BOD 5 test Biochemical Oxygen Demand LAGOON SAMPLING

43 43 TSS test Total Suspended Solids LAGOON SAMPLING

44 44 NH 3 test Colorimetric analysis LAGOON SAMPLING

45 45 PO 4 test Colorimetric analysis LAGOON SAMPLING

46 46 E. coli CFU/100 mL Important to know because of effect on human health but not a large contributor to oxygen demand LAGOON SAMPLING

47 47 Case Study: Role of Algae Particulates Weekly Sewage Load LAGOON SAMPLING

48 48 Case Study: Role of Algae 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

49 49 Case Study: Role of Algae 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

50 50 Case Study: Role of Algae Algae tend to increase the pH in the lagoon which favours volatile form of ammonia NH 4 + ↔ NH 3 + H + Ammonia exists in equilibrium between non-volatile (NH 4 + ) and volatile (NH 3 ) forms. At neutral pH, the non-volatile form is dominant LAGOON SAMPLING

51 51 Types of Lagoons Facultative Oxygen input from algae and wind is significant Odours generated in bottom layer are eliminated in overlying aerobic layer LAGOON DESIGN O2O2 O2O2 O2O2 O2O2 O2O2 ANAEROBIC

52 52 Types of Lagoons Anaerobic Oxygen input is relatively insignificant (organic load is too high) LAGOON DESIGN ANAEROBIC Odours

53 53 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) LAGOON DESIGN

54 54 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

55 55 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

56 56 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

57 57 Methane Gas capture California Manure Lagoon

58 58 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

59 59 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

60 60 Drummondville, QC WWTP m 3 /d V/Q = 11 days per lagoon Aeration intensity = 0.5 – 1.2 W/m 3

61 61 L’Assomption, QC Q design = 7700 m 3 /d

62 62 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

63 63 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

64 64 Seasonal Factors Temperature Biology Turnover Ice Cover Sunlight Photosynthesis affects pH and DO pH affects volatility and toxicity of ammonia LAGOON DESIGN

65 65 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

66 66 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

67 67 Desludging

68 68 Sludge Accumulation Slows down Solids accumulate in the lagoon sediments Rate of accumulation gradually slows due to digestion Drummondville, QC WWTP LAGOON DESIGN

69 69 Typical Wastewater Lagoon Design in Alberta LAGOON DESIGN

70 70 Quebec Design Criteria Facultative lagoons are designed based on loading rates of 22 to 12 kg BOD 5 /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

71 71 Quebec Design Criteria As is the case for Alberta, operational requirements are specified rather than effluent requirements. MENV guide suggests design gives effluent BOD 5 of mg/L and TSS of mg/L (depending on presence of algae) Data from installations in Quebec in 1990 had an average of 400 to 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

72 72 Quebec Design Criteria 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

73 73 Lagoon Design Poor design can lead to problems: Poor effluent quality Foul Odours Excessive sludge accumulation Uncontrolled discharge Uncontrolled seepage LAGOON DESIGN

74 74 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

75 75 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

76 76 Sewage Lagoon at Whale Cove, NU wetland Downstream wetland provides further treatment beyond the lagoon LAGOON DESIGN

77 77 Sewage Lagoon at Whale Cove, NU Lagoon effluent follows topography to ocean LAGOON DESIGN

78 78 Exfiltration Lagoon Performance Why wetlands do or do not work is a current topic of study. Important factors include: Loading (kg BOD 5 /m 2 ) Temperature Rate of Seepage over Year Exfiltration or uncontrolled runoff Retention time in downstream wetlands LAGOON DESIGN

79 79 Exfiltration LAGOON DESIGN

80 80 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

81 81 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

82 82 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

83 83 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

84 84 Exfiltration into surrounding Wetlands


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