Fenton and biological-Fenton coupled processes for textile wastewater treatment and reuse

Both Fenton oxidation and the combination of aerobic Sequencing Batch Reactor (SBR) + Fenton oxidation were investigated in a bench-scale study to degrade and reuse a real textile wastewater with a TOC = 465 mg L-1 C, COD = 2100 mg L-1 O-2 and Escherichia coli = 80,000 CFU mL(-1), according to RD 1620/2007 (Spanish Normative for wastewater reclamation and reuse). The independent variables considered for the optimization of the oxidative process were temperature, H2O2 and Fe (II) concentrations. Under the best stand-alone Fenton operating conditions: T = 25 degrees C, pH = 3; [H2O2] = 1650 mg L-1 and [Fe (II)]= 216 mg L-1, we achieved 64% TOC reduction and >99% E. coli removal. However, the best results were obtained when applying Fenton process with [H2O2] = 1518 mg L-1 and [Fe (II) = 66.5 mg L-1, as a biological polishing step. The aerobic biological treatment was conducted using a SBR with 1 day HRT. In this case 92% TOC and >99% E. coli removal were accomplished. The obtained results showed the feasibility of both processes to achieve suitable water qualities for internal reuse, according to RD 1620/2007. (C) 2011 Elsevier B.V. All rights reserved.