Textile wastewater treatment with activated sludge and powdered activated carbon

The objective of the study is to determine the effectiveness of batch activated sludge process and powdered activated carbon adsorption for organic and color removal from textile wastewaters. Factors affecting treatment performance investigated in the study included raw wastewater strength, various combinations of dye to starch in the wastewater, aeration time. Synthetic wastewaters using starch solution and disperse-red- -60 dye were used in the adsorption study. The 3 wastewater strengths used included low, medium and high strength. The 5 different dye to starch combinations used included 0% dye+100% starch, 25% dye+75% starch, 50% dye+50% starch, 75% dye+25% starch, and 100% dye+0% starch. The batch bio-oxidation was conducted for a period of 24 hours. The COD removal efficiency, color removal, bio-oxidation rate constant, F/M ratio, SVI, pH and temperature were determined. The results indicated that starch was much easier to remove by the batch activated sludge process compared to disperse-red-60 dye, which was virtually non-biodegrada- ble. Wastewaters containing 100% starch had the highest COD removal efficiency. Increase in dye concentration in wastewater resulted in decrease in the COD removal efficiency. The COD removal efficiency ranged from 6 to 45% for low strength wastewater of 100 mg/L COD, 27 to 80% for medium strength wastewater of 500 mg/L COD, and 23 to 65% for high strength wastewater of 1000 mg/L COD. The low strength wastewaters had the best settling characteristics, while the medium strength wastewater- s had the worst. For high PAC dosage of 15 g/L, high COD removal efficienci- es of 88 to 98% removal and Eab* of 36 to 47 were obtained. It is recommend- ed that activated sludge be used to remove high COD organic pollutants first, followed by PAC adsorption to remove dye waste in the treatment of textile wastewaters.