General nature of soluble and particulate organics in sewage and secondary effluent

Abstract The size distribution of collective organic parameters was analyzed for sewage and secondary effluent. One soluble and three particulate fractions were physically separated from each system by settlement and high speed centrifugation. In character, particulate solids were highly organic and soluble solids largely inorganic in both systems. COD/TOC ratios and carbon oxidation numbers showed that organic carbon in sewage was in a low state of oxidation, while that in effluent was in a relatively high state of oxidation. In both systems the oxidation state of carbon in soluble organics was distinctive from that in the particulate organics. Activated sludge treatment resulted in reduction of organic parameters in the order of COD> TOC> volatile solids. Treatment was considerably more efficient in reducing the concentration of particulate organics than in reducing the concentration of soluble organics.