Activated Sludge Process

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Activated Sludge Process
The activated sludge process is a wastewater treatment method in which the carbonaceous organic matter of wastewater provides an energy source for the production of new cells for a mixed population of microorganisms in an aquatic aerobic environment. The microbes convert carbon into cell tissue and oxidized end products that include carbon dioxide and water. Activated sludge plant involves wastewater aeration in the presence of a microbial suspension, solid-liquid separation following aeration, discharge of clarified effluent, wasting of excess biomass, and return of remaining biomass to the aeration tank. An important feature of the activated sludge-process is the formation of flocculent settleable solids that can be removed by gravity settling in sedimentation tanks. In activated sludge process wastewater containing organic matter is aerated in an aeration basin in which micro-organisms metabolize the suspended and soluble organic matter. Part of organic matter is synthesized into new cells and part is oxidized to CO2 and water to derive energy. In activated sludge systems the new cells formed in the reaction are removed from the liquid stream in the form of a flocculent sludge in settling tanks. A part of this settled biomass, described as activated sludge is returned to the aeration tank and the remaining forms waste or excess sludge. Activated Sludge Treatment Process Layout:

Biological Nutrient Removal Process
BNR processes are modifications of the activated sludge process that incorporate anoxic and anaerobic zones to provide nitrogen and phosphorous removal. In aerobic zones, oxygen is the electron acceptor, in anoxic zones, nitrate-N is the electron acceptor and in anaerobic zones neither oxygen nor nitrate-N is present. The division of the bioreactor to provide these alternative biochemical environments is the distinguishing feature of a BNR system. The aerobic zone is a necessary component of all BNR systems, while the...
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