275 ISSN 1063-455X, Journal of Water Chemistry and Technology, 2020, Vol. 42, No. 4, pp. 275–280. © Allerton Press, Inc., 2020. Optimizing the Fenton Based Pre-Treatment of Landfill Leachate Using Response Surface Methodology Parteek Singh Thind a and Siby John a, * a Civil (Environmental) Engineering Department, PEC University of Technology, Chandigarh, India *e-mail: johnsiby1@gmail.com Received July 10, 2017; revised March 24, 2018; accepted April 3, 2020 Abstract—Mixing of xenobiotic substances with the household waste decreases the biodegradability of leachate generated from municipal landfill sites. In various parts of the world, where solar energy is pervasive, solar photo Fenton-based pre-treatment of municipal landfill leachate can be considered as a potential pre-treatment method to improve its biodegradability. Therefore, this paper reports a lab- oratory study conducted to compare the efficiency of Fenton and Solar Photo Fenton processes to pre- treat leachate from municipal solid waste landfill site of Chandigarh, India. The operating parameters such as pH and initial concentrations of reagents (i.e., H 2 O 2 and Fe 2+ ) were optimized using a three level multivariate Box-Behnken statistical approach in combination with response surface methodology. After 2 h of treatment, at the optimal conditions of pH 3.4, [H 2 O 2 ] = 2.73 g/L and [Fe 2+ ] = 63.71 mg/L, 86.21% degradation of Chemical Oxygen Demand (COD) was observed after solar photo Fenton-based treatment. On the contrary, the final COD removal obtained using Fenton process at the optimal con- ditions, pH 5, [H 2 O 2 ] = 2.66 g/L, [Fe 2+ ] = 47.29 mg/L, was 59.19%. Further, this study showed that the Fenton based pre-treatment can enhance the biodegradability of landfill leachate. After pre-treat- ment, the Biological Oxygen Demand (BOD 5 ) to COD ratio of landfill leachate improved from 0.13 to 0.57 and 0.49 for solar photo Fenton process and Fenton process, respectively. Findings of this study will trigger the broader interest of the auditory comprising policy makers and scientists to treat the leachate using renewable sources and prevent contamination of groundwater. Keywords: biodegradability, Box-Behnken approach, Fenton process, landfill leachate, solar photo Fenton process, response surface methodology DOI: 10.3103/S1063455X2004013X INTRODUCTION Dumped toxic and recalcitrant substances on landfills may find their way into the leachate. Untreated leachate can percolate and contaminate the groundwater which can further cause numerous health impacts with a chain of events occurring between different environmental media [1, 2]. Among the various conventional treatment methods, biological treatment of leachate poses serious problems because of the presence of xenobiotic compounds. Therefore, numerous pre-treatment methods have been developed to enhance the biodegradability of leachate such as: chemical oxidation, electro- flocculation, ion exchange etc. [3]. Among these methods, chemical oxidation processes have gained popularity with Fenton-based processes offering great potential for landfill leachate pre-treatment [4, 5]. In Fenton-based processes, H 2 O 2 is a commonly used oxidizing agent which in presence of Fe 2+ leads to the production of , as shown in equations (1) (2) The Fe 3+ ions, produced according to Eq. (1), then form stable complexes with intermediate organic products, as shown in equation (3) i OH + + - + → + i 2 3 2 2 Fe HO Fe OH + OH, → + i i 2 RH + OH R H O. + - + + → 3 2 2 2 Fe RCO Fe(RCO ) . WATER TREATMENT AND DEMINERALIZATION TECHNOLOGY