Cotreatment of sewage and septage in waste stabilization ponds.

A one year study was carried out in a waste stabilization ponds system where septage and sewage are cotreated. The system consists of two septage ponds which operate alternately followed by two ponds in series which receive the combined effluent. The septage ponds also act as evaporation ponds for the accumulated sludge. The monitoring program was divided in two phases. The results of the first phase indicate that the effluent of septage ponds has an adequate quality to be discharged into the waste stabilization ponds designed to treat sewage and that is possible to use the septage ponds to dry the accumulated sludge. Further investigation is needed to find suitable post-treatment of the sludge in order to use it in agriculture.