Coagulation / flocculation process in the removal of trace metals present in industrial wastewater

Attempts were made in this study to examine the effectiveness of polymer addition to coagulation process during treatment of a beverage industrial wastewater to remove some of its trace metals content such as lead, cadmium, total iron, total chromium, nickel and zinc. Experiments were conducted using the standard Jar test procedure to determine the performance of both ferric chloride and organic polymer (a non-ionic polyacrylamide) individually and ferric chloride-polymer combination. The dosages used for ferric chloride ranged from 0 to 500mg/l, whereas polymer dosages varied between 0 and 100mg/l. The (optimal) removal efficiency for total chromium in the wastewater was obtained at 300mg /l for ferric chloride and 65mg/l for polymer. Whereas for zinc and total iron, the optimal removal efficiencies were obtained at 500mg/l for ferric chloride and 65mg/l for polymer. Addition of ferric chloride resulted in significant removal of the metals reaching up to 91%, 72% and 54% of total chromium, zinc and total iron respectively while addition of polymer achieved 95%, 87% and 88% of total chromium, zinc and total iron respectively. Ferric chloride produced more voluminous and more compacted sludge than polymer. Combinations of ferric chloride and polymer at different ratio achieved better removal efficiencies of the metals in the range 84-97% for total chromium, 69-90% for zinc and 69-92% for total iron, also less sludge was produced. Lead, cadmium and nickel were not detected in the raw wastewater