Development of a system for treatment of coconut industry wastewater using electrochemical processes followed by Fenton reaction Lúcio de Moura Gomes, José Leandro da Silva Duarte, Nathalia Marcelino Pereira, Carlos A. Martínez-Huitle, Josealdo Tonholo and Carmen Lúcia de Paiva e Silva Zanta ABSTRACT The coconut processing industry generates a significant amount of liquid waste. New technologies targeting the treatment of industrial effluents have emerged, including advanced oxidation processes, the Fenton reaction, and electrochemical processes, which produce strong oxidizing species to remove organic matter. In this study we combined the Fenton reaction and electrochemical process to treat wastewater generated by the coconut industry. We prepared a synthetic wastewater consisting of a mixture of coconut milk and water and assessed how the Fenton reagents’ concentration, the cathode material, the current density, and the implementation of associated technologies affect its treatment. Electrochemical treatment followed by the Fenton reaction diminished turbidity and chemical oxygen demand (COD) by 85 and 95%, respectively. The Fenton reaction followed by the electrochemical process reduced turbidity and COD by 93 and 85%, respectively. Therefore, a combination of the Fenton and electrochemical technologies can effectively treat the effluent from the coconut processing industry. Lúcio de Moura Gomes Nathalia Marcelino Pereira Technology Center, Federal University of Alagoas – Campus A.C. Simões, CEP 57072-970, Maceió-Al, Brazil José Leandro da Silva Duarte Josealdo Tonholo Carmen Lúcia de Paiva e Silva Zanta (corresponding author) Institute of Chemistry and Biotechnology, Federal University of Alagoas – Campus A.C. Simões, CEP 57072-970, Maceió-Al, Brazil E-mail: zanta@hotmail.com Carlos A. Martínez-Huitle Institute of Chemistry – Federal University of Rio Grande do Norte – Campus Universitário s/n, CEP 59078-970, Natal-RN, Brazil Key words | coconut industry wastewater, Dimensionally stable anodes, electrochemistry, Fenton reaction INTRODUCTION The growing population has increased the demand for food pro- duction, especially industrial products. The food industry is one of the largest industries in the world and generates large amounts of wastewater, which requires appropriate treatment to avoid environmental problems. The coconut processing industry produces a significant amount of wastewater. How- ever, little information exists on the composition of the effluent, possibly because it is complex; it usually contains large quantities of oils and greases and displays high biochemi- cal oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC) and turbidity as well as a significant concentration of suspended solids (Callado & Paula ). Procedures that can efficiently treat effluents are manda- tory. Recent research has shown that advanced oxidation processes (AOPs) and combined processes are as advan- tageous as traditional methods. Chemical treatments can enhance the biodegradability of recalcitrant compounds while reducing the treatment time necessary to accomplish traditional biological processes (García-Montaño et al. ). AOPs involve the generation of strong oxidizing species, such as the hydroxyl radical ( • OH), which has high oxidizing power and can degrade several polluting compounds that resist conventional processes. The hydroxyl radicals can originate from the reaction between hydrogen peroxide and ferrous salts at pH 3.0 ± 0.1 (Brillas et al. ). Equation (1) shows the reaction involving the Fenton reagent: Fe 2þ þ H 2 O 2 ! Fe 3þ þ  OH þ OH  (1) After the Fenton reaction, a series of chain reactions regenerate the Fenton reaction catalyst (Fe 2þ ) and produce 2258 © IWA Publishing 2014 Water Science & Technology | 69.11 | 2014 doi: 10.2166/wst.2014.129 Downloaded from https://iwaponline.com/wst/article-pdf/69/11/2258/470716/2258.pdf by guest on 30 May 2020