Author's personal copy Journal of Hazardous Materials 181 (2010) 127–132 Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Coagulation–Fenton coupled treatment for ecotoxicity reduction in highly polluted industrial wastewater J.A. Perdigón-Melón ∗ , J.B. Carbajo, A.L. Petre, R. Rosal, E. García-Calvo Department of Analytical Chemistry and Chemical Engineering, University of Alcalá, 28871 Alcalá de Henares, Spain article info Article history: Received 20 November 2009 Received in revised form 16 March 2010 Accepted 27 April 2010 Available online 2 May 2010 Keywords: Cosmetic industry wastewater Total phenol Coagulation Fenton’s reagent Ecotoxicity abstract A coupled coagulation–Fenton process was applied for the treatment of cosmetic industry effluents. In a first step, FeSO 4 was used as coagulant and the non-precipitated Fe 2+ remaining in dissolution was used as catalyst in the further Fenton process. In the coagulation process a huge decrease in total organic carbon (TOC) was achieved, but the high concentration of phenol derivatives was not diminished. The decrease in TOC in the coagulation step significantly reduces the amount of H 2 O 2 required in the Fenton process for phenol depletion. The coupled process, using a H 2 O 2 dose of only 2 g l −1 , reduced TOC and total phenol to values lower than 40 and 0.10 mg l −1 , respectively. The short reaction period (less than 15 min) in TOC and phenol degradation bodes well for improving treatment in a continuous regime. The combination of both processes significantly reduced the ecotoxicity of raw effluent and markedly increased its biodegradability, thus allowing easier treatment by the conventional biological units in conventional sewage treatment plants (STPs). © 2010 Elsevier B.V. All rights reserved. 1. Introduction During the last century, industrial activity increased the demand for fresh water, whereas generated wastewater was discharged into water bodies, thereby affecting the fragile aquatic ecosys- tem. Growing concern about these problems in both developed and developing countries is leading to more stringent regulations with regard to public and industrial wastewater disposal. One sec- tor of special interest is the soap and cosmetic industry which generates wastewater characterized by high COD (chemical oxy- gen demand), mainly proceeding from the cleaning processes of batch reactors and mixers, which has to be washed before reuse. Cosmetics contain non-easily biodegradable xenobiotics including many toxic chemical compounds such as preservatives (normally phenol derivatives), mixtures of surfactants, dyes, fragrances and co-solvents which makes conventional biological treatment diffi- cult [1,2]. Usual treatments of cosmetic industry effluents involve processes such as chemical oxidation [1,3], membrane technology [4], adsorption [5–7], flotation [8] or coagulation [9]. Among the currently used unit processes in wastewater treat- ment, coagulation has received considerable attention due to its high COD and TOC removal efficiency and cost effectiveness. The effectiveness of TOC removal by coagulation processes varies with the nature of the organic compounds as well as with water prop- ∗ Corresponding author. Tel.: +34 91 885 4973; fax: +34 91 885 5088. E-mail address: ja.perdigon@uah.es (J.A. Perdigón-Melón). erties such as alkalinity or hardness [10,11]. Phenols in particular are hardly removed in the coagulation process and as a result these compounds exceed the discharge limits of local legislation [11]. In order to improve the efficiency of phenol removal, the use of Fenton followed by a coagulation process has been proposed [12–14]. This oxidation method is based on the use of a mixture of Fe 2+ /H 2 O 2 in acidic conditions that generates a high concentration of hydroxyl radicals, the particular feature which defines advanced oxidation process (AOP). Fenton processes have been widely studied in the degradation of phenol derivatives [15–17] and in the treatment of wastewater from the cosmetics industry [1,18,19]. The high COD concentration typically found in industrial cosmetic effluent requires the use of large amounts of H 2 O 2 , an expensive chemical which would limit the practical application of the Fenton process. As stated above, the presence of toxic substances in industrial wastewater would not only have a detrimental effect on aqueous ecosystems but also on the activated sludge process of conven- tional (STPs) [20]. Chemical analysis is still predominantly used to assess the degree of water pollution [21]. However, this traditional approach fails to provide an adequate interpretation of toxicity to biota due to mixture effects [22–24]. In fact, the ecotoxicity of a complex mixture of chemicals is influenced by the additive, syn- ergic or antagonic relations between components, which makes it a complex task to elucidate the toxicity of a mixture from that of individual chemicals [25]. Ecotoxicity bioassays provide a direct means of assessing the effect of wastewater on the aquatic environ- ment by considering different issues such as metabolic variations, mortality, mobility, and the growing capacity or breathing rate of 0304-3894/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2010.04.104