Effect of shock-loading of heavy metals on total organic carbon and phosphate removal in an anaerobic-aerobic activated sludge process.

The effect of shock-loading of zinc, copper and cadmium ions on the removal of total organic carbon (TOC) and phosphate in an anaerobic-aerobic activated sludge process was investigated. TOC removal was not sensitive to shock-loading of Zn(2+) and Cd(2+) ions, and complete removal was achieved even at 20 mg Zn(2+)/l and 20 mg Cd(2+)/l. However, with over 1 mg Cu(2+)/1 TOC removal efficiency decreased. PO inf4 (sup3-) removal, in contrast, was extremely sensitive to these metal ions, with the threshold being 1 mg Zn(2+)/l and 1 mg Cd(2+)/l. Higher concentrations adversely affected PO inf4 (sup3-) removal. Copper again proved detrimental; no PO inf4 (sup3-) removal was achieved even at 1 mg Cu/l. These results highlight the sensitivity of the removal efficiencies of TOC and PO inf4 (sup3-) to shock loadings of these heavy metals.