Predicting metals partitioning in wastewater treatment plant influents

Interactions of heavy metals with primary sludge particulates were investigated using batch equilibrium metal uptake experiments. Results showed that metal uptake by primary sludge is significantly affected by pH. A mathematical model was developed to describe metals partitioning as a function of pH. The metal adsorption constants were determined. Results showed that for the same metal ion, the values of metal adsorption constants for primary sludge samples collected from different locations and at different times were in the same order of magnitude. Therefore, the adsorption constants were normalized and calibrated using field data. For Ag(I), Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II), the calibrated values of adsorption constants (log KS) are, respectively, 4.4, 5.1, 3.6, 4.5, 4.6, 3.6, 6.0, and 6.0. These constants can be used to predict the metal partitioning in plant influents and metal removal in primary treatment processes.