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Oxidation ponds
This document discusses different types of oxidation ponds used to treat wastewater through natural biological processes. There are four main types: aerobic ponds which use algae and bacteria to treat water and are shallow; anaerobic ponds which do not require oxygen and break down waste through methane production; facultative ponds which contain both aerobic and anaerobic zones; and maturation ponds which further treat effluent to remove pathogens. Together, these pond systems provide effective wastewater treatment through natural microbial activity and sunlight.
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Oxidation ponds
- 1. Oxygen PondsOxygen PondsOxygenPondsOxygen Ponds
- 2. Oxidation Ponds What areOxidation Ponds ? •Oxidation Ponds are large earthen basins in which waste water is treated by natural processes involving bacteria and in many instances algae. •These are shallow basins used to treat raw water •Rate of waste oxidation is slower in Oxidation Ponds
- 3. Types Of Oxidationponds • Aerobic Ponds • Anaerobic Ponds • Facultative Ponds • Maturation or Tertiary Ponds
- 4. Aerobic Ponds • Theaerobic ponds are large in dimension & shallow pond that used for wastewater treatment by natural process involving both algae and bacteria. New Algae Algae O2 Bacteria CO2, NH3, PO4, H2O New Bacteria Organic Bacteria Solar Energy
- 5. Design Considerations Parameter Value Depthin mts. 0.15 - 0.5 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
- 6. Anaerobic Ponds • AnaerobicPonds requires no Dissolved Oxygen 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. • These ponds are basically Sedimentation ponds • High waste water loading which depletes all O2 • Solids settles in pond basin • Anaerobic digestion of sludge occurs in pond bottom
- 7. Large Organic Loading O2Req > O2 Supply Enhanced H2S- Formation Increase In Turbidity Reduced Light Penetration Reduced Photosynthesis Reduced O2 Formation Anaerobic Conditions how anaerobic conditions occurs in oxidation ponds?
- 9. Anaerobic digestion process •Hydrolysis - Complex organics (proteins and fats) broken down to simpler compounds by various bacteria • Acidogenesis (Fermentation) – Fatty acids and alcohols oxidized, amino acids and carbohydrates fermented , forms volatile fatty acids and hydrogen • Acteogenesis – conversion of complex fatty acids to acetic acid • Methnogenesis - conversion of acetic acid to methane and CO2 and CO2 ,H2S to methane
- 10. Process • When temperaturerises above 15o C digestion generates enough biomass which causes pond surface to bubble – biogas (70% CH4 and 30% CO2) • Digested solids accumulate – cleanout in 1 to 3 years
- 11. Pond Characteristics • Hydraulicdetention time is short – 1 day • Depth – 2 to 5 m (usually 3m) • Design is highly empirical – based on volumetric load (gm BOD/m3 /day) • For e.g. 100 gm BOD/m3 /day to 3 m deep pond=3000 kg/ha/day
- 12. Role of pH •Below pH 7.0 then H2S forms and causes odor • Below ph 6.2 then conditions became toxic
- 13. ADVANTAGES •Gives energy whereasaerobic requires energy. •Very high concentration can be treated efficiently whereas not possible in aerobic ponds. LIMITATIONS •Standard BOD cannot be maintained under anaerobic process as suspended solid increased. •Organic matter convert to CO2, CH4 which is difficult to separate from bacteria.
- 14. Facultative Ponds • Theseare 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 aerobic during day time. In the remaining hours the pond bottom may turn anaerobic. • Top Pond water is aerobic and supports very high density algal population • Bottom water is an anaerobic condition in which sludge is digested • Algae generate O2 by photosynthesis during the day ,which is useful for oxidation of waste by bacteria • Bacteria degrade waste, uses O2 and generates CO2, algae use CO2 and generate O2
- 15. Wind CO2 Anaerobi cZoneAerobic 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 Sunlight
- 16. Maturation / TertiaryPonds • These are similar to aerobic ponds but are very lightly loaded with organic wastes. • Generally used for upgrading effluents from conventional secondary treatment processes. • The principal purpose is to achieve reduction in fecal colliform count and remove nitrogen and phosphorus. • Used to remove pathogenic bacteria and viruses (99.9997%) - e-Coli removal • Solar disinfection – using UV light • 1 m deep • Total detention time of the order of 10 days • Disinfection may be used, if required
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