Heavy Metal Balance in a Communal Wastewater Treatment Plant

Abstract

Heavy metal removal from a municipal wastewater treatment plant was evaluated in the given study. The aim of the work was to find water or sludge streams in the technology that could be treated separately for heavy metal removal to maximise the efficiency of the entire treatment. The results proved that in the plant studied 70–80% of the metal content was discharged. Only 5–20% was retained in the digested sludge. A small percentage of the metal content of the influent could only be measured in the primary and secondary sludges. Otherwise, there were very similar metal concentrations in these sludge streams. The reject water exhibited an inconsiderable level of metal recycling in the technology, no more than 2–3% of the influent load. Some 2–10% of the heavy metal content of the inlet was removed from the sand trap. We did not find the separate heavy metal removal from the sludge streams efficient as most of the heavy metal load finally was discharged from the treatment plant with the treated effluent into the recipient.