Decolorization and detoxification of textile wastewater by ozonation and coagulation processes

The aim of this work is to evaluate and compare the performance of ferrous and aluminum sulfate coagulations and ozonation treatment techniques. The evaluation of treatment efficiency was made using the parameters of oxygen demand (COD), color absorbances at 436 nm, 525 nm and 620 nm and Daphnia magna toxicity test. Approximately 50-60% color, 60% COD and 70-80% toxicity were removed at 1000 mg L-1 and 1500 mg L-1 ferrous and aluminum sulfate, respectively. However, these required doses for optimum toxicity reduction are not economical due to the chemical sludge production. Ozonation was relatively effective in reducing color absorbances and toxic effects of textile effluents. Almost complete color absorbances (over 98%) were removed in 20 min ozone contact time, while COD removal (37%) was very low and almost stable in 30 min ozonation period. The toxicity of wastewater reduced after color degradation by 85% at the transferred ozone (TrO3) concentration of 82.3 mg L-1. (C) 2004 Elsevier Ltd. All rights reserved.