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Biological Treatment

Biological treatment process is essentially an aerobic biochemical oxidation’ or aeration. In this process,sewage water is filtered through specially designed sprinkling filters so that aerobic conditions are maintained all the times. During this aerobic oxidation process, the carbon of the organic matter is converted in to CO, ; the nitrogen into NH3 and finally into nitrites and nitrates. The dissolved bases present in the sewage water then forms salts such as ammonium nitrite, ammonium nitrate, calcium nitrate, etc. Thus :


NH2CONH2 ————-  CO, + 2NH3

(Urea) (aerobic)


NH3 ————– HNO3, HNO2, etc.


HNO3, HNO2 ——–— NH4NO2, NH4NO3, Ca(NO2) 2,Ca(NO3) 2, KNO2, etc.

Trickling filters are mostly employed for this.

aerobic oxidation

Aerobic oxidation

anerobic biological

anerobic biological