Coagulation and precipitation of a mechanical pulping effluent—II. Toxicity removal and metal salt recovery

• Published in: Water research (Oxford) 1996, Vol.30 (4), p.793-798
• Main Authors: Stephenson, Robert J., Duff, Sheldon J.B.
• Format: Article
• Language: English
• Subjects: aluminum; Aluminum compounds; Applied sciences; chemical precipitation; Coagulation; Exact sciences and technology; Hazardous materials; Industrial wastewaters; iron; Iron compounds; mechanical pulping; metal salts; metals; Pollution; precipitation; pulp and paper mill effluents; pulp effluent; Q1; Salts; Toxicity; wastewater treatment; Wastewaters; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/0043-1354(95)00214-6

Pulp and paper effluents contain a number of compounds which are harmful to receiving waters and which are inhibitory or recalcitrant to biological treatment. Iron and aluminum coagulating agents were effective in treating a CTMP/BCTMP pulping effluent in batch jar screening tests. For full strength effluent, toxicity was markedly reduced by precipitation, with optimal Microtox EC50 values of approx. 20% being recorded. Dilution of the effluent followed by precipitation further improved toxicity removal, and complete detoxification of 1 4 strength effluent was observed using ferric chloride as the precipitant. At higher than optimal levels of addition, iron and aluminum salts contributed to toxicity. The possibility of salt recovery was demonstrated through a fixed solids balance. Ferric chloride appeared to be the most promising candidate for recovery, with less than 20% of the fixed solids lost to the supernatant.