| Abstract: | Two types of wastewaters from the dye manufacturing process were treated by multistage chemical coagulation combined with ozonation. By using the coagulant iron(II) chloride and a commercial coagulant aid, the majority of COD was removed in advance of ozonation, a similar repeated 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. The decolorization efficiency was >99% and the COD elimination was >90%. The multistage combined chemical coagulation ozonation treatment was found to be superior to the single-stage treatment. © 1998 SCI. |
