Advanced oxidation of commercial textile biocides in aqueous solution: effects on acute toxicity and biomass inhibition I. Arslan-Alaton, G. Eremektar, F. Germirli-Babuna, G. Insel, H. Selcuk, B. Ozerkan and S. Teksoy Istanbul Technical University, Faculty of Civil Engineering, Department of Environmental Engineering, 34469 Maslak, Istanbul, Turkey (E-mail: arslanid@itu.edu.tr; geremektar@ins.itu.edu.tr; fgbabuna@ins.itu.edu.tr) Abstract In the present study, the decomposition of two biocides used in the textile finishing process with Advanced Oxidation Processes (AOPs) has been studied. Different AOPs, i.e O 3 /OH 2 , TiO 2 /UV-A and Fe 2 þ /H 2 O 2 have been used representing mutually combined components of the chemically and photochemically driven advanced oxidation systems. The course of reaction was examined by changes in chemical oxygen demand (COD), total organic carbon (TOC) and acute toxicity towards the water flea Daphnia magna (assessed in terms of the effective dilution ratio LD 50 ). Particular attention has been paid to determine the inhibitory effect of raw and ozonated biocides on biological activated sludge consortium at concentrations typically encountered in textile finishing effluents. Significant oxidation and mineralization of both biocides could be achieved employing ozonation at pH ¼ 11.5 and heterogeneous photocatalysis (TiO 2 /UV-A) at pH ¼ 5.0, whereas Fenton’s reagent appeared to be less effective in COD and acute toxicity abatement. Keywords Advanced Oxidation Processes (AOPs); biocides; inhibition; Daphnia magna; oxygen uptake rate; textile finishing agents; toxicity Introduction The textile dyeing and finishing industry has a very high water demand usually being well over 100 litres per kg of finished products (Easton, 1995; Orhon et al., 2003). Of particular concern is the complex and refractory nature of some effluent streams originat- ing from the dyeing and finishing stages thus making their activated sludge treatment a difficult task (Eckenfelder and Mustermann, 1995; Germirli Babuna et al., 1999). Much less attention has been paid so far to textile finishes that are applied to a wide range of textile fabrics so as to impart them a powerful and long-term antibacterial and antifungal protection. Biocides are extensively used as antibacterial finishing agents in the textile sector to control microbial growth on hospital fabrics, socks, underwear and sportswear. The excessive use of biocides in different industrial applications is likely to lead to environmental, ecological and toxicological problems when wastewaters generated from these processes are directly discharged to natural water or municipal sewers (Fernandes- Alba et al., 2002). The antimicrobial action of biocides involves the alteration of enzy- matic functions, extracellular nutrient transport and removal of metabolic cell products (Villegas-Navarro et al., 2001). For instance, in toxicity bioassays conducted on antifoul- ing biocides and their biological degradation products it could be established that the majority of tested biocides and their degradation products possessed nonspecific toxic activity and also showed synergistic enhancement of toxicity towards battery bioassays (Sakkas and Albanis, 2003). Increasing interest in applying so-called Advanced Oxidation Processes (AOPs) to purify different kinds of organic and inorganic micropollutants almost non-selectively at very high rates (bimolecular reaction rate constant < 10 9 2 10 11 M 21 s 21 ) has recently Water Science & Technology Vol 52 No 10–11 pp 309–316 Q IWA Publishing 2005 309 Downloaded from http://iwaponline.com/wst/article-pdf/52/10-11/309/433697/309.pdf by guest on 11 December 2023