The effect of pre-ozonation on the H₂O₂/UV-C treatment of raw and biologically pre-treated textile industry wastewater

Advanced chemical oxidation of raw and biologically pretreated wastewater by ozonation, H₂O₂/UV-C treatment and the successive combination of ozonation and H₂O₂/UV-C oxidation was investigated. For the raw textile wastewater, the application of successive O₃ + H₂O₂/UV-C oxidation enhanced the COD and TOC removal efficiency of the H₂O₂ (50mM)/UV-C process by a factor of 13 and 4, respectively. In case of the biotreated textile wastewater, the preliminary ozonation step increased COD removal of the H₂O₂(10mM)/UV-C treatment system from 15% to 62%, and TOC removal from 0% to 34%, but did not appear to be more effective than applying a single ozonation process in terms of TOC abatement rates. Enhancement of the biodegradability was more pronounced for the biologically pre-treated wastewater with a two fold average increase in the BOD₅/COD ratio for the studied chemical oxidation systems.