Oxidation Ditch
⇒ Dr Pasveer and his associates have developed this method for the treatment of sewage of small estates and colonies.
⇒ It is nothing but a modified form of a normal activated sludge plant. This process is simpler as no primary treatment is given to the sewage.
⇒ The oxidation ditches are in the shape of long continuous channels (150 to 1000 m long) usually oval in plan. They are of a trapezoidal cross-section of relatively shallow depth (1 to 5 m wide and 1 to 1.5 m deep) forming a continuous circuit. One or two surface rotors are placed across the channel.
⇒The sewage is aerated by rotors. After aeration, the sewage is allowed to settle down in settling tanks. The activated sludge is returned to the aeration units. The aerators are stopped for two hours and suspended solids settle down.
⇒The effluent and excess sludge are removed and disposed of width or without treatment. The oxidation ditch normally employs a detention period up to 24 hours.
⇒The oxidation ditch can remove suspended solids up to 95 %. It is suitable for small communities or small industries.