A critical analysis of the alternative treatments applied to effluents from brazilian textile industries.

Abstract

The textile industry wastewater is highly harmful to the environment when it is discharged in its raw state, since it might contain dyes, surfactants, and other dissolved compounds that adversely affect the aquatic ecosystems. Based on the low biodegradability of textile effluents, physicochemical processes (e.g. coagulation-flocculation) are usually indicated and eventually combined with biological treatment, which is applied at full scale due to lower costs. However, the conventional processes have limitations, of which it can highlight the low color removal and formation of residual sludge. The present work consists of a critical analysis about the alternative processes evaluated to treat effluents generated by mills of the Brazilian textile sector, an important industrial segment of this country. It was verified that the advanced oxidation processes (AOPs), as the electrooxidation, photo-Fenton and classical Fenton oxidation have been the most effective in reducing color (average above 90%),

and organic matter (average above 78%) from such effluents. In addition, coagulation-flocculation with plant- derived inputs, electrocoagulation and unconventional bacterial systems are alternatives that have also been

quite efficient. Analyzing the characteristics of secondary effluents of biological systems normally used to treat textile effluents, it was observed that some still have relevant concentrations of pollutants. Therefore, AOPs have

been also evaluated as a polishing step to treat them, which were effective to comply with the Brazilian envi- ronmental agencies for its disposal in water bodies. Some works described the possibility of reusing the treated

effluents, showing that many of the alternative processes are also promising in this regard.