Modification of Activated Sludge Process, Hydrostatic, Eutrophication, Microorganisms, Oligotrophic, Inorganic Nutrients

Modification of Activated Sludge Process

	Modification of Activated Sludge Process This process was developed by Union Carbide and uses oxygen instead of air for aeration. Closed tanks and specially designed stirring system prevent the wastage of oxygen. Deep shaft process developed by Imperial Chemical Industry uses injection of oxygen and achieves high oxygen solubility by increasing hydrostatic pressure through a vigorous circulation pattern. Some more advancements in the ASP have been developed that include anaerobic stages also.
In the anaerobic stage, dilute sewage passes through a dense stationary anaerobic biomass which minimises reactor volume and manimises the efficiency of digestion process. Bacteria involved tend to form granules. Besides reducing the BOD, advanced activated sludge secondary treatment (ASST) also removes inorganic nitrogen and phosphorous which when present in the sewage effluent is concerned with the phenomenon of eutrophication' of natural waters. Eutrophication is a process where water becomes rich in nutrients and is a natural sequence in aquatic environment. Deep, cool, nutrient-poor water becomes shallower, warmer and more eutrophic and settles, and organic matter accumulates from biological production. Eventually, lake is filled in. Sudden nutrient enrichment through sewage discharge triggers explosive algal blooms.
As a result there is mutual shedding of microorganisms and exhaustion of micronutrients. Toxic products increase eventually and algal population crashes. Decomposition of dead algal biomass by heterotrophs exhausts the dissolved oxygen in the water, leading to septic conditions. Many natural oligotrophic lakes are limited by P/N but if the sewage effluent supplies large amount of these inorganic nutrients, eutrophication response is likely to occur. Obvious remedy is to remove the causative inorganic nutrients from the sewage discharges.

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Modification of Activated Sludge Process