Application of Advanced Oxidation Technologies for Decolorization and Mineralization of Textile Wastewaters

Abstract

Reactive dyes are the most abundantly used in textile industry due to their high color fastness, wide color spectrum as well as low energy consumption. The presence of these dyes in effluent released into receiving waters has become a serious environmental problem not only related to their color but mainly because of the hazardous byproducts. An environmentally sustainable development policy in textile industry requires development of new technologies to reduce water consumption as well as negative environmental impact of discharged wastewater. Advanced oxidation processes (AOPs) are the most promising technology for decolorization and mineralization of wastewater contamination. This paper presents the results of ozonation, Fenton’s oxidation and H₂O₂/UV treatment of simulated as well as industrial textile wastewater containing Reactive Black 5. The AOPs were carried out under varied process parameters such as: dye concentration, pH, oxidant and detergent doses and wide range concentration of NaCl. The decolorization was followed by absorbance while oxidation and mineralization progress by COD and TOC measurements respectively. The almost completely inhibition of decolorization in the presence of NaCl in concentration usually used in industry (60 - 80 g/L) was observed for Fenton reagent. The slight inhibition was observed for H₂O₂/UV system while for ozonation there was no influence of NaCl on the decolorization. The similar relationship of the influence of anionic detergent concentration was observed. The experiments indicated that ozonation is the best method from TOC and COD removal point of view. For the decolorization of real textile effluents two streams were used 1) containing C.I. Reactive Yellow 145, Red 195, Blue 221 and 2) Reactive Black 5. As a result of the treatment, almost complete decolorization of the wastewater was obtained. Considering both the experimental results and technological problems, it can be presumed that advanced oxidation with a application of ozone or hydrogen peroxide/UV are a very promising techniques for potential industrial implementation, however from economic point of view the more reasonable is the ozonation process.