Degradation and toxicity reduction of textile effluent by combined photocatalytic and ozonation processes.

To minimize the environmental impact of textile effluents, mainly related to their high coloration and the presence of toxic or carcinogenic reactive dyes, the efficiency of photochemical and ozonation processes, applied in the form of isolated and combined procedures, were evaluated. The investigation was focused on the reduction of total organic carbon content (TOC), color and acute toxicity (monitoring by inhibition of Escherichia coli respiration). For a reaction time of 60 min, the anatase TiO2-assisted photocatalytic process produces color and TOC reduction of about 90% and 50%, respectively. Meanwhile, the ozonation process gives a decolorization of about 60% but negligible TOC reduction. When the processes were applied in a simultaneous form, the decolorization was almost complete and the TOC reduction was higher than 60%. The three treatments studied yield an acute toxicity reduction of around 50%.