Advanced oxidation of raw and biotreated textile industry wastewater with O3, H2O2 /UV‐C and their sequential application

Abstract

The advanced chemical oxidation of raw and biologically pretreated textile wastewater by (1) ozonation, (2) H2O2 /UV − C oxidation and (3) sequential application of ozonation followed by H2O2 /UV − C oxidation was investigated at the natural pH values (8 and 11) of the textile effluents for 1 h. Analysis of the reduction in the pollution load was followed by total environmental parameters such as TOC, COD, UV–VIS absorption kinetics and the biodegradability factor, fB. The successive treatment combination, where a preliminary ozonation step was carried out prior to H2O2 /UV − C oxidation without changing the total treatment time, enhanced the COD and TOC removal efficiency of the H2O2 /UV − C oxidation by a factor of 13 and 4, respectively, for the raw wastewater. In the case of biotreated textile effluent, a preliminary ozonation step increased COD removal of the H2O2 /UV − C treatment system from 15% to 62%, and TOC removal from 0% to 34%. However, the sequential process did not appear to be more effective than applying a single ozonation step in terms of TOC abatement rates. Enhancement of the biodegradability factor (fB) was more pronounced for the biologically pretreated wastewater with an almost two-fold increase for the optimized Advanced Oxidation Technologies (AOTs). For H2O2 /UV − C oxidation of raw textile wastewater, apparent zero order COD removal rate constants (kapp), and the second order OH· formation rates (ri) have been calculated. © 2001 Society of Chemical Industry