An aluminum smelting facilities producing 165,000 t/a aluminum via electrolysis, 285,000 t/a foundry products and thereby recycling 120,000 t/a aluminum scrap needs to treat 43,000 m3/a wastewater. The wastewater contains high amounts of aluminum (up to 50 mg/L), zinc and other heavy metals e.g. chromium, copper, cadmium, cobalt and lead.
The current facility includes a multi-stage flocculation at several pH-steps via iron salt and various polymeric flocculants. Not only threshold values for metals were not reached, but relatively high concentrations of fluorides were also measured in downstream.