This project developed models to predict the distribution of metals in activated sludge system process streams. The data used to develop the models were obtained through extended pilot studies from a previous project. The objectives of the study were to evaluate the effects of wastewater and plant operational variables on the distribution of selected metals between the soluble and solid phases of the process streams of a conventional activated sludge system, and to develop an empirical model which describes the metals distribution in the individual treatment system process streams. The patterns of metals transport across the treatment systems were extremely interesting. The range of concentrations for each metal was quite broad, reflecting the combination of natural fluctuations in the influent metals levels, and the dosing with mixtures of metals in the laboratory. There was a reduction in the average total metal concentration across the primary clarifier. The difference between the total and soluble metals concentration is the concentration of solids-bound metal. The total concentrations of metals in the mixed liquids are much higher than in the raw waste, typically by 5- to 10-fold. Two empirical metals distribution models have been developed which are believed to be generally acceptable. Both models accurately predict the distribution of process stream metals between the soluble and solid phases.