Treatment of dairy industry wastewater by variations of coagulation-flocculation and ozonation

Abstract

In this study, COD removal efficiencies were investigated in dairy industry wastewater by using variations of coagulation-flocculation and ozone oxidation in laboratory. Coagulation-flocculation (CF), ozonation (O), ozonation following coagulation-flocculation (CF+O) and coagulation-flocculation following ozonation (O+CF) processes were applied to the wastewater. Optimum pH and optimum dosages were studied at various pH values and at various coagulant doses at room temperature (25oC). In ozone oxidation, wastewater was taken to ozonation reactor and ozone was given 1 g/hour dose and COD removal efficiencies were determined by taking samples in 15, 30, 45, 60, 90, 150, 210 and 240 minutes. Treatment performance of coagulation and flocculation and ozonation processes and their variations were evaluated by COD removal efficiencies. The optimum pHs for the Al2(SO4)3 and FeCl3 were found as 7 and 6 respectively. The optimum dosages were 1200 mg/L for Al2(SO4)3 and 500 mg/L for FeCl3. At optimum conditions, approximately 45% and 28% of COD were removed by using FeCl3 and Al2(SO4)3 respectively. When only ozonation was applied, COD removal efficiency was determined as 20% at the end of 240 minutes. COD removal efficiency was 65% with the application of ozonation after coagulation-flocculation (CF+O). When the coagulation-flocculation process was applied after the ozonation process (O+CF), COD removal efficiency remained at 52%.