Performance of passive aerated immobilized biomass reactor coupled with Fenton process for treatment of landfill leachate Sherif Ismail * , Ahmed Tawfik Egypt-Japan University of Science and Technology (E-JUST), Environmental Engineering Department, P.O. Box 179, New Borg El Arab City, 21934, Alexandria, Egypt article info Article history: Received 12 November 2015 Received in revised form 5 April 2016 Accepted 5 April 2016 Keywords: Landfill leachate Fenton reaction Passive aerated immobilized biomass Empirical model abstract The passive aerated immobilized biomass (PAB) reactor was investigated for the treatment of landfill leachate. Reactor performance was affected by hydraulic retention time (HRT), organic loading rate (OLR), volatile suspended solids to total suspended solids ratio (VSS/TSS) and COD total /NH 4 -N ratio. COD total and NH 4 -N removal efficiency dropped from 55 ± 6 to 33 ± 2% and from 93 ± 8 to 80 ± 11%, when the HRT was decreased from 16 to 4 h, respectively. Ammonia oxidation increased from 69 to 94% at decreasing the VSS/TSS ratio from 0.54 to 0.24, respectively. Fenton pre-treatment substantially improved the removal efficiency of COD total (83 ± 4%) and COD soluble (83 ± 5%). The simple empirical model designed to assess the performance of PAB reactor treating landfill leachate showed good agreement between pre- dicted and experimental parameter values. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Landfills are widely used for solid waste disposal in developing countries. However, landfill leachates which are generated by chemical and biological decomposition of solid wastes are impor- tant sources for aquifer and surface water contaminants (Zhao et al., 2010). The composition of landfill leachate varies depending on the types of disposal of solid wastes, soil characteristics, rainfall pat- terns and landfill age. Landfill leachate is usually characterized by offensive odor, high ammonia-nitrogen content, inorganic salts, heavy metals and complex chemical composition (Cassano et al., 2011). Consequently, treatment of landfill leachate is essential to reduce the environmental impacts and meet legislated standards for discharge into natural water streams. Several technologies have been proposed for treatment of landfill leachate, such as biological processes i.e. anaerobic (Kawai et al., 2012), aerobic suspended carrier biofilm (Welander et al., 1997) and combination of anaerobic-aerobic processes (Kettunen et al., 1996), physical and/or chemical processes i.e. adsorption by activated carbon (Foo and Hameed, 2009), advanced oxidation process (Rocha et al., 2011) and coagulationeflocculation (Boumechhour et al., 2013) and a combination of biological and physicochemical treatment methods i.e. a combination of photo-chemical oxidation with biological processes (Koh et al., 2004) and adsorption with biological pro- cesses (Kargi and Pamukoglu, 2003). Generally, application of bio- logical treatment alone is not satisfactory due to the leachate characteristics. A combination of different processes is preferred. Moreover, it is necessary to develop and create a novel treatment system which is reliable, simple and less energy consuming. Recently, immobilized biomass reactors have been considered one of the most advantageous technologies for treatment of wastewater containing organic and inorganic compounds (Tawfik and ElBatrawy, 2012). This is mainly due to high removal efficiencies of carbonaceous and nitrogenous organic compounds present in wastewater in addition to the relatively low cost in comparison with other treatment techniques (El-Kamah et al., 2011). Several researchers have investigated the treatment of landfill leachate using attached growth systems such as trickling filters (Knox, 1985), submerged aerobic biological filters (Pedersen, 1992) and rotating biological contactors (Spengel and Dzombak, 1991). These systems have the advantage of not suffering from loss of active biomass due to poor separability, and nitrification in attached growth systems has been shown to be less affected by low temperatures than in suspended growth systems (Knox, 1985). In this study, a passive aerated immobilized biomass (PAB) reactor was developed for treatment of landfill leachate, a tech- nology not yet reported in the literature for treatment of landfill * Corresponding author. E-mail addresses: sherif.ismail@ejust.edu.eg (S. Ismail), ahmed.tawfik@ejust. edu.eg (A. Tawfik). Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod http://dx.doi.org/10.1016/j.ibiod.2016.04.010 0964-8305/© 2016 Elsevier Ltd. All rights reserved. International Biodeterioration & Biodegradation 111 (2016) 22e30