Experiments on attached-growth waste stabilization ponds (AGWSP) were conducted to investigate the performance of AGWSP units that received Cd and Cr shock loadings. Under the experimental conditions employed in this study, the laboratory-scale and pilot-scale AGWSP units had less concentrations of the applied heavy metals present in the effluents than those in the effluents of the waste stabilization pond (WSP) units without attached-growth media. The superior performance of the AGWSP units was due to adsorption of the applied heavy metals on the attached-growth media. An empirical model was developed which could satisfactorily predict heavy metal concentrations in the AGWSP and WSP effluents after heavy metal shock loadings.