ponds and lagoons
- 1. A Presentation on Oxidation Ponds & Lagoons
- 2. Oxidation Ponds What are Oxidation Ponds ? Oxidation Pond is an open, flow through earthen basin of controlled shape specially design and constructed to treat sewage and bio-degradable industrial waste by natural processes involving bacteria and in many instances algae.
- 3. Types Of Oxidation ponds Aerobic Ponds Anaerobic Ponds Facultative Ponds Maturation or Tertiary Ponds
- 4. Applications Type of Ponds Applications Aerobic Nutrient removal, treatment of soluble organic waste & effluents from waste water treatment plants. Anaerobic Treatment of domestic and industrial wastes. Facultative Treatment of untreated screened waste water and industrial wastes.
- 6. Aerobic Ponds The aerobic pond is shallow pond in which light penetrates to the bottom there by maintaining active algal photosynthesis through out the entire system. Aerobic Ponds contain dissolved oxygen (DO) throughout the entire depth of the pond all the time. Treatment is accomplished through the stabilization of organic wastes by aerobic bacteria and algae.
- 7. Dissolved oxygen can be introduced into a pond through several means: Algae, like other plants, emit dissolved oxygen as a by-product of photosynthesis. Wind, blowing across the surface of a pond, will cause oxygen to be absorbed into the water. Mechanical aeration devices agitate the water surface to cause spray and waves so that oxygen can be absorbed from the air. Some mechanical devices include paddle wheels, mixers, and rotating brushes. Diffused aeration utilizes a blower system to discharge air into the water. The air stream is broken into fine bubbles; the smaller the bubbles, the greater the oxygen transfer.
- 8. ALGAE AEROBIC BACTERIA Light Energy from Sun New Algal Biomass New Bacterial Biomass Organics from Waste Water
- 9. Variations in Aerobic Ponds Diurnal(daily) variation in DO concentration Diurnal variation in pH Extreme values of these, in either direction may be detrimental to microbial activity.
- 10. Design Considerations Parameter Value Depth in mts. 0.15-.5 Retention time (day) 2-6 BODu loading( lb/acre-day) 100-200 BODu removal(%) 80-90 Algae concentration(mg/l) 100-200 Re-circulation ratio 0.2-2.0 Effluent suspended solids concentration(mg/l) 150-350
- 12. Anaerobic Ponds These ponds requires no D.O. for microbial activity as the organisms use O2 from compounds such as NO3, SO4 as their hydrogen acceptors and give end product such as methane, carbon dioxide etc.
- 13. Anaerobic Ponds function without dissolved oxygen (DO) throughout any of its depth. Treatment is accomplished by anaerobic bacteria at the bottom of the pond, which ferment the sludge. Anaerobic ponds have a depth of eight (8) to twenty (20) feet, and a typical detention time of 20 to 50 days. A deep sludge blanket covers the bottom of these ponds, while a scum layer covers the surface. The scum layer is important to the pond because: It helps to minimize offensive odors It blocks transfer of DO through surface contact It helps insulate the pond or lagoon to ensure ideal conditions for sludge fermentation.
- 14. Anaerobic decomposition It take place in two separate but inter related steps :- 1. Decomposition of dissolved organic waste by acid producing bacteria to organic acids (such as acetic propionic acid) and, 2. Further decomposition of these acids to the end products of methane, carbon dioxide and water by methane producing bacteria.
- 15. Acid producing Bacteria Methane producing bacteria H2O, CO2, CH4 Organic Wastes H2O, CO2 Bacterial Cells Bacterial Cells
- 16. Facultative Ponds Facultative Ponds contain a supernatant (upper) layer that is aerobic, and lower layers that are anaerobic. These are neither fully aerobic nor fully anaerobic. They are often about 1 to 2 m in depth and favor algal growth along with the growth of aerobic, anaerobic and facultative microorganisms. Such ponds are predominantly aerobic during day light as well as for some hours of the light. In the few remaining hours the pond bottom may turn anaerobic.
- 17. Zones of facultative pond 1) Aerobic zone 2) Anaerobic zone 3) Facultative zone The decomposition of incoming organic waste and products of anaerobic decomposition is done by facultative bacteria.
- 18. Wind CO2 Anaerobi c Zone Aerobic Zone Anaerobi c Zone Facultative Zone O2 alga e (CO2, NO2, PO4, SO4) Aerobic Bacteria Biomass Biomass Anaerobic Bacteria Sludge Blanket Organic acids & Compounds of C, N, P, S Impermeable lining Sunligh t
- 19. Maturation / Tertiary Ponds These are similar to aerobic ponds but are very lightly loaded with organic wastes. Generally used for upgrading effluents from conventional secondary treatment processes.
- 20. Reasons For Poor Performance of Oxidation Pond DO level in the pond during night & early morning hours was almost zero. BOD removal efficiency was only 60-70%
- 21. LAGOONS LAGOONS Lagoons are deep waste stabilization ponds -like bodies of water or basins designed to receive, hold, and treat wastewater for a predetermined period of time by artificial means of aeration. In the lagoon, wastewater is treated through a combination of physical, biological, and chemical processes.
- 22. TYPES OF LAGOONS TYPES OF LAGOONS According to the microbial activity in the aerated lagoons- Aerobic aerated lagoons. Facultative aerated lagoons.
- 23. AEROBIC AERATED LAGOONS AEROBIC AERATED LAGOONS Dissolved oxygen is present throughout much of the depth of aerobic lagoons. They tend to be much shallower than other lagoons. They are better suited for warm, sunny climates, where they are less likely to freeze. HRT = 2 to 10 days SS concentration between 60 to 300mg/l The BOD removal is of order of 75 to 85% Oxygenation requirement is of order of .7 to 1.3 kg per kg of BOD removed.
- 24. Units of aerobic lagoon 1) The mechanical surface aerators so that solids do not settle to bottom of tank. 2) The other unit is settling tank for removal of suspended solids .
- 25. FACULTATIVE AERATED LAGOONS FACULTATIVE AERATED LAGOONS Three types of zones are present Aerobic Zone. Anaerobic Zone. Facultative Zone. HRT is higher than aerobic lagoons because time requires for the solids to settle and for many pathogens viruses to either die off or settle out.
- 26. Facultative lagoons Detentions time ranges from 3 to 5 days . BOD removal are of order 75 to 90%
- 28. Two, Three, or Four Lagoons Are Better Than One Two, Three, or Four Lagoons Are Better Than One Each lagoon cell has a different function to perform, and a different kind of lagoon design may be used for each cell. In Series When lagoons operate in series, more of the solid material in the wastewater, such as algae, has an opportunity to settle out before the effluent is disposed of. In Parallel This system design is particularly useful in cold climates or where lagoons are covered with ice for parts of the year
- 30. Operation And Maintenance Operation And Maintenance For Aerobic Lagoons Any earthen structures used as impoundments must be periodically inspected. If left unchecked, rodent damage can cause severe weakening of lagoon embankments. In submerged diffused aeration, the routine application of HCl gas in the system is used to dissolve accumulated material on the diffuser units The use of submerged perforated tubing for diffused aeration requires maintenance and cleaning on a routine basis to maintain design aeration rates
- 31. Operation And Maintenance For Facultative Lagoons Most facultative lagoons are designed to operate by gravity flow. The system is not maintenance intensive and power costs are minimal because pumps and other electrically operated devices may not be required. Earthen structures used as impoundments must be inspected for rodent damage.
- 32. Applicability Applicability Type of Lagoon Application Aerobic Lagoon Municipal and industrial wastewaters of low to medium strength. Facultative Lagoon Treated raw, screened, or primary settled municipal wastewater and biodegradable industrial wastewaters.
- 33. Limitations For Aerated Lagoons Aerated lagoons may experience ice formation on the water surface during cold weather periods Reduced rates of biological activity also occur during cold weather Formation of ice on Floating Aerators. For facultative Lagoons The inability of the process to meet a 30 mg/L limit for TSS due to the presence of algae in the effluent. Odors may be a problem in the spring and fall during periods of excessive algal blooms and unfavorable weather conditions
- 34. Thanks