Modeling the fate of metals in municipal water pollution control plants

Abstract

ABSTRACT: A solution of seven metal salts was dosed into batch and continuous‐flow dynamic wastewater experiments at bench‐ and pilot‐scale to calibrate a computer‐based mathematical model for predicting the fate of metals in municipal water pollution control plants (WPCPs). The model accounts for both precipitation and sorption onto primary and secondary sludges, and predicts the concentrations of metals in the primary sludge, return activated sludge, and secondary clarifier effluent. In dynamic step experiments, six of seven metals were removed substantially (55–99%) by the pilot activated sludge system. Lead and chromium were removed to the greatest extent while nickel was least removed. With the exception of nickel, a large fraction of the effluent metal concentrations were in particulate form. Below the solubility limits, a linear sorption model generally was able to simulate the observed effluent response to a step input. Sampling at a full‐scale WPCP was conducted for testing the steady‐state model's predictive capability. Except for lead, the predicted effluent concentrations agreed well with observed values.