The conventional activated sludge process is designed with an aim of treating domestic and industrial wastewater by using biological flocs, mainly composed of protozoa and bacteria along with air which aids oxidation.
It is a type of aerobic treatment process with long aerobic detention time to generate lesser sludge and avoid primary settling basins. These are designed for lower F/M ratios and very high SRTs (of the range of 3 to 4 weeks).
It is generally designed with an aim of oxidizing carbonaceous biological substance, nitrogenous matter (which mainly comprises of ammonium and nitrogen). When designed, constructed, operated and maintained well, it also helps in removing nutrients like nitrogen and phosphorous by a considerable margin.
It generally consists of an aeration tank where in oxygen is injected in the Mixed Liquor Suspended Solids and a clarifier which is used to catalyse the settling of biological flocs. Hence, separates the biological floc formations from the clear or treated water. In order to trat the phosphate and/or nitrogenous matter an additional step is performed wherein mixed liquor is subjected to an anoxic condition whose duration is specific to the quantity and characteristic of the influent wastewater.