Conversion of Anodizing Sludge into Aluminum Sulphate for Use in Waste Water Treatment

Abstract

During the process of aluminium surface treatment, a large quantity of aluminum-rich sludge is generated and its disposal is a great challenge to the respective industry.  The main objective of this study was to investigate the potential of environmental pollution reduction by recovery of aluminum from the anodizing sludge in the form of alum for use in waste water treatment. Both waste water and dumped sludge from various sampling locations in the plant were characterized. Waste water effluents were analyzed for temperature, pH, total suspended solids, total dissolved solids, turbidity, dissolved oxygen, biological oxygen demand and chemical oxygen demand. The final effluent temperature was 28.7±5.8^oC which was within permitted levels while the pH was 5.8±0.4. The total suspended and dissolved solids were significantly high at 690.6±183.7 and 4619.8±0.23mg/L respectively. The sludge from the dumpsite had solids content ranging from 13.73% to 16.80%. Recovery of aluminium from sludges obtained from the dumpsite, wastewater treatment plant and from mixed effluent emanating from process tanks were 87.1%, 77.4% and 64.26% respectively. The prepared alum had higher content aluminium metal and coagulation performance of the prepared alum compared well with that of the commercial alum. Jar tests gave reduction in waste water pollution and the optimum settling dosage, pH, temperature and time were 8g/L, 6.5, 40^oC and 20 minutes respectively.