MULTISTAGE TREATMENT OF HIGH-STRENGTH DYE WASTE-WATER BY COAGULATION AND OZONATION

Two types of wastewaters from the dye manufacturing process were treat ed by multistage chemical coagulation combined with ozonation. By usin g the coagulant iron (II) chloride and a commercial coagulant aid, the majority of COD was removed in advance of ozonation, a similar repeat ed treatment cycle was performed after settlement of the coagulant in each cycle. Results showed that the optimum concentrations to be used were 2.5 % (v/v) iron (II) chloride and 35 mg dm(-3) coagulant aid. Th e decolorization efficiency was > 99 % and the COD elimination was > 9 0 %. The multistage combined chemical coagulation ozonation treatment was found to be superior to the single-stage treatment. (C) 1998 SCI.