Anaerobic Pond in Wastewater Treatment
DEFINITION
ANAEROBIC POND
Anaerobic ponds are deep treatment ponds that exclude oxygen and encourage the growth of bacteria, which break down the effluent. It is in the anaerobic pond that the effluent begins breaking down in the absence of oxygen "anaerobically". The anaerobic pond acts like an uncovered septic tank. Anaerobic bacteria break down the organic matter in the effluent, releasing methane and carbon dioxide. Sludge is deposited on the bottom and a crust forms on the surface as show in Fig. 2.
Fig. 2 Operation of the Anaerobic Pond.
Anaerobic ponds are commonly 2-5 m deep and receive such a high organic loading (usually >100g BOD/m3 d equivalent to >3000 kg/ha/d for a depth of 3 m). They contain an organic loading that is very high relative to the amount of oxygen entering the pond, which maintains anaerobic conditions to the pond surface. Anaerobic ponds don’t contain algae, although occasionally a thin film of mainly Chlamydomonas can be seen at the surface. They work extremely well in warm climate (can attain 60-85% BOD removal) and have relatively short retention time (for BOD of up to 300 mg/l, one day is sufficient at temperature >20oC).
Anaerobic ponds reduce N, P, K and pathogenic micro-organisms by sludge formation and the release of ammonia into the air. As a complete process, the anaerobic pond serves to: * Separate out solid from dissolved material as solids settle as bottom sludge. * Dissolve further organic material. * Break down biodegradable organic material. * Store undigested material and non-degradable solids as bottom sludge. * Allow partially treated effluent to pass out.
CONCEPT: * BOD Removal Rates and Factors
First the concept of Biological Oxidation Demand (BOD) should be introduced. Organic compounds in wastewater may be used as food for bacteria, which can biochemically digest or oxidize the organic compounds to produce energy for growth. This oxidation of organic material, if done under aerobic
ANAEROBIC POND
Anaerobic ponds are deep treatment ponds that exclude oxygen and encourage the growth of bacteria, which break down the effluent. It is in the anaerobic pond that the effluent begins breaking down in the absence of oxygen "anaerobically". The anaerobic pond acts like an uncovered septic tank. Anaerobic bacteria break down the organic matter in the effluent, releasing methane and carbon dioxide. Sludge is deposited on the bottom and a crust forms on the surface as show in Fig. 2.
Fig. 2 Operation of the Anaerobic Pond.
Anaerobic ponds are commonly 2-5 m deep and receive such a high organic loading (usually >100g BOD/m3 d equivalent to >3000 kg/ha/d for a depth of 3 m). They contain an organic loading that is very high relative to the amount of oxygen entering the pond, which maintains anaerobic conditions to the pond surface. Anaerobic ponds don’t contain algae, although occasionally a thin film of mainly Chlamydomonas can be seen at the surface. They work extremely well in warm climate (can attain 60-85% BOD removal) and have relatively short retention time (for BOD of up to 300 mg/l, one day is sufficient at temperature >20oC).
Anaerobic ponds reduce N, P, K and pathogenic micro-organisms by sludge formation and the release of ammonia into the air. As a complete process, the anaerobic pond serves to: * Separate out solid from dissolved material as solids settle as bottom sludge. * Dissolve further organic material. * Break down biodegradable organic material. * Store undigested material and non-degradable solids as bottom sludge. * Allow partially treated effluent to pass out.
CONCEPT: * BOD Removal Rates and Factors
First the concept of Biological Oxidation Demand (BOD) should be introduced. Organic compounds in wastewater may be used as food for bacteria, which can biochemically digest or oxidize the organic compounds to produce energy for growth. This oxidation of organic material, if done under aerobic