Treatment of laundry waste-water by electrocoagulation

BACKGROUND: The present study describes an electrocoagulation process for treating laundry waste-water using aluminum plates. The effect of various parameters such pH, voltage, hydraulic retention time (HRT), and number of aluminum plates between the anode and cathode on efficiency of treatment are investigated. RESULTS: Experimental results showed that by increasing HRT, treatment efficiency increases but beyond 45 min changes are negligible. Among the results for chemical oxygen demand (COD), phosphorus, detergent, colour and turbidity, the lowest decrease was found for phosphorus. The larger the HRT, the greater the electrical current needed to achieve constant voltage and temperature in the system. The pH of the influent is a very significant variable which affects the treatment of laundry waste-water considerably, the optimal range being 6.0-8.0. In addition, it was found that the pH increases from 8.3 to more than 10 over the first hour of treatment after which the pH remains relatively constant. Finally, kinetic analysis indicates that the adsorption system obeys a second-order kinetic model. CONCLUSION: The aluminum hydroxide generated in the cell decreases the concentration of pollutants in laundry waste-water to a permissible level. It is concluded that, compared with other treatment processes, electrocoagulation is more effective in treating laundry waste-water under appropriate conditions. (C) 2011 Society of Chemical Industry