Integrated photochemical and biological treatment of a commercial textile surfactant: Process optimization, process kinetics and COD fractionation

The biodegradability of surfactants is a frequent and complex issue arising both at domestic as well as industrial treatment facilities. In the present experimental study, the integrated photochemical (H2O2/UV-C) and biochemical (activated sludge) treatment of a commercial grade nonionic/anionic textile surfactant formulation was investigated. Photochemical baseline experiments have shown that once the initial pH and H2O2 dose were optimized, practically complete COD removal (COD0 = 500 +/- 30 mg L-1) could be achieved. Once the COD was elevated to values being typical for the textile fabric preparation stage, treatment efficiency was seriously retarded provided that the photochemical treatment conditions remained constant. Moreover, a definite relationship existed between H2O2 consumption and COD removal for H2O2/UV-C advanced oxidation of the textile surfactant. In the second part of the study, COD abatement was modeled for the biodegradation of untreated and photochemically pretreated textile surfactant formulation according to their COD fractions. Results have indicated that the readily biodegradable and rapidly hydrolysable COD fractions of the textile surfactant solution could be appreciably increased upon exposure to an optimum H2O2 concentration (60 mM; i.e. 2.1 g H2O2 (g COD0)(-1)) and extended UV-C irradiation times (i.e. 90 and 120 min). (c) 2007 Elsevier B.V. All rights reserved.