Photo-Fenton and sequencing batch reactor coupled to photo-Fenton processes for textile wastewater reclamation: Feasibility of reuse in dyeing processes

Abstract Both photo-Fenton oxidation and the combination of aerobic sequencing batch reactor (SBR) + photo-Fenton processes were investigated in a bench-scale study to degrade and reuse a real textile wastewater with Total Organic Carbon (TOC) = 390 mg L −1 , Chemical Oxygen Demand (COD) = 1560 mg L −1 O 2 and Escherichia coli  = 80000 CFU mL −1 in further dyeing processes. The independent variables considered for the evaluation of the oxidative process were temperature, H 2 O 2 and Fe (II) concentrations. Required treated water qualities were determined by both RD 1620/2007 (Spanish Normative for wastewater reclamation and reuse) and specific water qualities for internal reuse. The best results were obtained when applying photo-Fenton process as a polishing step, where previous aerobic SBR under 1 day hydraulic retention time (HRT), gave 75% TOC reduction after 25 cycles. The further photo-Fenton process coupled under: ([Fe (II)] = 66.5 mg L −1 ; [H 2 O 2 ] = 1518 mg L −1 ; T  = 25 °C and pH = 2.7) conditions, achieved final COD and TOC reductions of 97 and 95% respectively. E. coli was fully removed according to specific normative. Finally, in order to accomplish specific water qualities for 100% internal reuse, resultant water was further conditioned by reverse osmosis and reused in bench-scale simulated dyeing processes, providing similar dyeing results in terms of K / S than those obtained by using fresh water.