Research article Treatment of an actual slaughterhouse wastewater by integration of biological and advanced oxidation processes: Modeling, optimization, and cost-effectiveness analysis Ciro Fernando Bustillo-Lecompte a , Mehrab Mehrvar b, * a Graduate Programs in Environmental Applied Science and Management, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canada b Department of Chemical Engineering, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canada article info Article history: Received 3 June 2016 Received in revised form 13 July 2016 Accepted 14 July 2016 Available online 29 August 2016 Keywords: Slaughterhouse wastewater Anaerobic digestion Activated sludge Advanced oxidation processes Process optimization Combined processes abstract Biological and advanced oxidation processes are combined to treat an actual slaughterhouse wastewater (SWW) by a sequence of an anaerobic baffled reactor, an aerobic activated sludge reactor, and a UV/H 2 O 2 photoreactor with recycle in continuous mode at laboratory scale. In the first part of this study, quadratic modeling along with response surface methodology are used for the statistical analysis and optimization of the combined process. The effects of the influent total organic carbon (TOC) concentration, the flow rate, the pH, the inlet H 2 O 2 concentration, and their interaction on the overall treatment efficiency, CH 4 yield, and H 2 O 2 residual in the effluent of the photoreactor are investigated. The models are validated at different operating conditions using experimental data. Maximum TOC and total nitrogen (TN) removals of 91.29 and 86.05%, respectively, maximum CH 4 yield of 55.72%, and minimum H 2 O 2 residual of 1.45% in the photoreactor effluent were found at optimal operating conditions. In the second part of this study, continuous distribution kinetics is applied to establish a mathematical model for the degradation of SWW as a function of time. The agreement between model predictions and experimental values in- dicates that the proposed model could describe the performance of the combined anaerobiceaerobic eUV/H 2 O 2 processes for the treatment of SWW. In the final part of the study, the optimized combined anaerobiceaerobiceUV/H 2 O 2 processes with recycle were evaluated using a cost-effectiveness analysis to minimize the retention time, the electrical energy consumption, and the overall incurred treatment costs required for the efficient treatment of slaughterhouse wastewater effluents. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Slaughterhouse wastewater (SWW) effluents are becoming one of the major agribusiness concerns because of the elevated amounts of water used during slaughtering, processing, and cleaning of the abattoir facilities. Although physical, chemical, and biological treatment can be used for SWW degradation, each treatment process has different benefits and drawbacks depending on the SWW characteristics, best available technology, jurisdic- tions, and regulations (Tabrizi and Mehrvar, 2004; Barrera et al., 2012; Franke-Whittle and Insam, 2013; Bustillo-Lecompte and Mehrvar, 2015; Valta et al., 2015; Bustillo-Lecompte et al., 2015, 2016a, 2016b). However, adopting combined processes for SWW treatment is considered operationally and economically advanta- geous because it incorporates and optimizes the advantages of different technologies to achieve high-quality effluents from in- dustrial and high-strength wastewaters (Kurian et al., 2006; Mehrvar and Tabrizi, 2006; De Nardi et al., 2011; Bustillo- Lecompte et al., 2013, 2014; Bustillo-Lecompte and Mehrvar, 2015; Mowla et al., 2014). Anaerobic treatment is the preferred biological treatment because of its effectiveness in treating high-strength wastewater such as SWW with less complex equipment requirements. Never- theless, anaerobically treated effluents of SWW require post- treatment to comply with required discharge limits (Cao and Mehrvar, 2011; Bustillo-Lecompte et al., 2013, 2014). Therefore, aerobic treatment systems are more frequently used in wastewater treatment since they operate at higher rates than conventional anaerobic treatment methods in the case of lower strength wastewaters. Taking into account that oxygen requirements and * Corresponding author. E-mail address: mmehrvar@ryerson.ca (M. Mehrvar). Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman http://dx.doi.org/10.1016/j.jenvman.2016.07.044 0301-4797/© 2016 Elsevier Ltd. All rights reserved. Journal of Environmental Management 182 (2016) 651e666