Research and practical application have shown that improvements in secondary sedimentation tank design features and proper preparation of the biological floc can yield tertiary quality secondary effluents.1,2 Improvement in effluent quality has been demonstrated for both the activated sludge (AS) and trickling filter/solids contact (TF/SC) processes. Secondary effluents can be produced which meet 10 mg/L suspended solids (SS) requirements without further treatment such as effluent filtration.