Free Activated Sludge Treatment Essay Sample

Wastewaters involve a large spectrum of different organic compounds depending on the scheme of production. The activated sludge process is the preferred treatment scheme for effective removal of organic matter through the aeration of wastewater mixed with reused biological sludge full of living microorganisms . The biological solids then separate from the treated wastewater in a clarifier and return to the aeration process. The microorganisms mix thoroughly with the incoming organic material, wherein they grow and reproduce using the organic material as food. Once flocculated, the living organisms readily settle in the secondary clarifiers. The waste water flows continuously into an aeration tank, where injected air mixes the wastewater with the returned activated sludge. The activated sludge treatment relates to the nitrogen cycle in the removal of nitrogen.
When the microorganisms oxidize ammonia present in the incoming organic material, they convert ammonia to nitrite and then to nitrate in aerobic conditions. In anaerobic conditions, the process of denitrification takes place in which nitrate converts into nitrogen in the absence of oxygen . The mixture of activated sludge and wastewater in the aeration tank, also called as mixed liquor flows into a secondary clarifier where the activated sludge settles. The activated sludge consists of organic solids in addition to bacteria, fungi, protozoa, nematodes and rotifers . A number of factors that affect the activated sludge treatment are temperature, return rates, amount of oxygen, amount of organic matter, pH, waste rates, wastewater toxicity and aeration time. The actual operation of the activated sludge system depends on three major factors, such as the quantity of the air supplied to the aeration tank, rate of activated sludge recirculation and the amount of excess sludge withdrawn from the system.

References

Orhon, Derin, Fatos Germirli Babuna and Ozlem Karahan. Industrial Wastewater Treatment by Activated Sludge. IWA Publishing, 2009.
Spellman, Frank R. Water and Wastewater Treatment Plant Operations. CRC Press, 2008.