Biological treatability and environmental impact of ozonation of spent reactive dyebaths

The effect of ozonation of spent reactive dyebaths on both subsequent biological wastewater treatment systems and ultimate aquatic toxicity of effluents from the wastewater treatment plant was determined. Actual spent dyebaths from a textile plant were ozonated to remove color. The ozonated and untreated control dyebaths were diluted to produce wastewaters similar in dissolved solids content to wastewaters typically discharged by a textile plant. These wastewaters were subjected to biological treatment, and effluent generated by the biological treatment was tested for toxicity to Ceriodaphnia dubia (C dubia). Higher reproduction in the ozonated wastewaters compared to those receiving only biological treatment suggested that ozonation of the spent dyebath tended to reduce the toxicity imparted by the wastewater after biological treatment.