Upgrading of decentralized ponds for municipal wastewater treatment and restricted reuse

Upgrading of a pond system for municipal wastewater treatment in a decentralized area is evaluated. The pond was constructed for the treatment of 63 m(3)/d. Currently it receives 83 m(3)/d, therefore poor treatment efficiency was recorded. An expansion of 1.6 times the present land area was required. In addition to construction, operation and maintenance were required to meet the permissible limits. The other option was to introduce aeration system to the ponds without any additional requirements. The efficiency of the successive treatment steps on the wastewater quality, including metals in the treated effluent/sludge and bacterial counts, was evaluated for agricultural reuse. The physical, chemical and bacterial parameters as well as the input aeration load (h) during the study period were investigated extensively. The results indicated that remarkable improvement in the treated effluent was achieved after upgrading the pond system via aeration. The removal rate of the pollution parameters ranged from 75 to 85%. The level of heavy metals in the produced sludge was below the permissible concentration and does not represent any risk. Meanwhile, it was possible to avoid any requirements for addition land area or construction of treatment and proved that the treated effluents can be reused for restricted water reuse.