Polishing of biologically treated textile wastewater through AOPs and recycling for wet processing

After biological treatment, different advanced oxidation processes (AOPs) were used to treat the real textile dyeing wastewater as a final step to remove color, COD and other refractory organic compounds, which were partially removed using a biological process. In this study, biologically treated effluent obtained from a textile industry was treated for recycling in textile wet processing for dyeing. The wastewater presents a lilac color, with an average chromaticity number (DFZ) of 100.8, alkaline pH (7.9), COD value of 186.5 mg/L, and total organic carbon (TOC) of 62.3 mg/L. Closed water loop recycling solution after trying a number of treatment option is proposed for achieving sustainability in industrial water consumption. UV/H2O2/O3 was evaluated as the most effective combination with reuse potential of 663,000 m3/year (with 85% water recovery, 100% color, and 60.1% COD removal) whereas the performance of ozone (O3), ozone/ultraviolet (O3/UV) and ozone/hydrogen peroxide (O3/H2O2) was almost the same. However, highest color and COD removals were achieved using Fenton oxidation but reusability potential was zero. Treated wastewater (by O3, O3/UV, UV/H2O2/O3, O3/H2O2) was safely recycled for dyeing purposes with 35% and 20% less NaCl and Na2CO3 addition to dye bath, respectively. The estimated saving was calculated as 122,400 US$/year for this reduction.