Caption title. At head of title: Project summary. Distributed to depository libraries in microfiche. "Sept. 1983." "EPA/600-S2-83-051."

This project assessed the variables influencing 'the removal of metals through combined industrial-municipal treatment plants. The metals investigated were: aluminum, cadmium, chromium, copper, iron, lead, nickel, and zinc. The metals were studied at subtoxic influent concentrations, and the interrelationships which influence metal removal were assessed. The research was performed in two phases. Phase I involved batch studies on raw sewage and activated sludge, to identify and define the impact of individual chemical and physical parameters on metals removal. These batch studies consisted of three parts. In Part A, metal solubility in filtered raw sewage and secondary effluent was determined as a function of pH. Part B investigated the equilibrium sorption of the test metals onto primary sewage solids and onto activated sludge solids. In Part C, the effect of sewage variables such as detergent and ammonia concentration on metal sorption was evaluated. In Phase II, eight pilot treatment plants, each consisting of primary clarifier, aeration basin, and secondary clarifier, were operated at varying influent metal levels to study the effect of significant variables indicated from the Phase I results., The results of this project indicate that the removal of metals in combined industrial-municipal treatment systems is influenced by a number of wastewater and treatment plant operation characteristics. The principal parameters controlling metal partitioning for each metal investigated were the total metal and suspended solids concentrations. The segregation of influent metals between the sludge (primary and secondary) phases and the plant effluent can be predicted, based upon the relationships identified in this study.