1 / 84

Lagoon Design and Performance

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

selene
Télécharger la présentation

Lagoon Design and Performance

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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

  2. Outline • Lagoon Performance • Biology • Lagoon Design • Operation and Sampling

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

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

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

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

  7. Biological Activity Bacteria consume soluble matter and fine particulates and then settle to bottom, which clears up water top layer Bacteria Consume Solubles and Fine Particulates Bacteria Grow and Settle Particulates LAGOON PERFORMANCE

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

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

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

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

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

  18. Bacteria Algae are photosynthetic bacteria that produce oxygen Bacteria consume organic matter and nutrients Bacteria work fastest with oxygen but can work without – which can lead to foul odours LAGOON BIOLOGY

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

  20. Biological Activity: Big and Small Bacteria 0.001 mm Protozoa, Rotifers 0.1 mm Daphnia 1 mm Geese – 1 m LAGOON BIOLOGY

  21. 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

  22. 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

  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 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

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

  25. 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 LAGOON BIOLOGY

  26. 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? Examples: Proteins Carbohydrates Toilet Paper Wood Plastic AEROBIC REACTIONS ANAEROBIC REACTIONS LAGOON BIOLOGY

  27. Treatment Steps : Gas Transfer • Ammonia can be removed by volatilization but it depends on pH • Useful to know what pH is… NH+4 NH3 + H+ LAGOON BIOLOGY

  28. Influent Fractions Total Influent COD Biodegradable COD Unbiodegradable COD Particulate Unbiodegradable Soluble Unbiodegradable Soluble Readily Biodegradable Particulate Slowly Biodegradable COD (Chemical Oxygen Demand) is a measure of all the organic matter in a sample LAGOON SAMPLING

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

  31. 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

  32. Biochemical Oxygen Demand (BOD5) Case study – shows DO “sag” due to BOD discharge http://www.oxscisoft.com/hermes/casestudies.htm

  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. Chinese Lake choked with Algae Nutrients: N and P

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

  37. Fish Kills Toxicity: Ammonia

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

  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. Seasonal Factors Snowmelt Dilution Biological Activity (nitrification) Averages of 3-years of measurements effluent of 1st lagoon at Drummondville (2000-2003) LAGOON SAMPLING

  41. COD test Chemical Oxygen Demand LAGOON SAMPLING

  42. BOD5 test Biochemical Oxygen Demand LAGOON SAMPLING

  43. TSS test Total Suspended Solids LAGOON SAMPLING

  44. NH3 test Colorimetric analysis LAGOON SAMPLING

  45. PO4 test Colorimetric analysis LAGOON SAMPLING

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

  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. 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. 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 LAGOON SAMPLING

More Related