Modeling the integrated heterogeneous catalytic fixed-bed reactor and rotating biological contactor system for the treatment of poorly biodegradable industrial agrochemical wastewater I.A. Vasiliadou, M.I. Pariente, F. Martinez, J.A. Melero, R. Molina* Department of Chemical and Energy Tech., Chemical and Environmental Tech., Mechanical Tech. and Analytical Chemistry, ESCET, Rey Juan Carlos University, 28933 Móstoles, Madrid, Spain A R T I C L E I N F O Article history: Received 16 February 2016 Received in revised form 7 April 2016 Accepted 7 April 2016 Available online 8 April 2016 Keywords: Agrochemical wastewater Catalytic wet hydrogen peroxide oxidation (CWHPO) Rotating biological contactors (RBC) Kinetic modeling A B S T R A C T An integrated system based on a heterogeneous catalytic wet hydrogen peroxide oxidation (CWHPO) and subsequent rotating biological contactors (RBCs) has been modeled for the treatment of agrochemical wastewater. One dimensional pseudo-homogeneous model was proposed for the CWHPO step. The reaction rate for TOC removal (k 1 ) was 0.087 1/min. In the case of the RBCs, two different approaches were considered: the pseudo-homogeneous model was based on Kornegy and Clark equations and it is restricted to only one substrate limitation, TOC, for the microbial growth. The microbial growth was modeled by a Monod type equation. The uptake rate and saturation coefficient values were P = 0.94 g/dm 2 d and Ks = 0.53 g/dm 3 . The integrated non-pseudo-homogeneous model considers a two-phase bioreactor in which all the biochemical processes occur in the solid biofilm phase. In this model, processes such as biofilm growth and diffusion of nutrients into biofilm were taken into account. The microbial growth was modeled using a double Monod equation with substrate limitation by TOC and total nitrogen (TN). Both approaches were able to describe the CWHPO-RBCs performance at different operating conditions with an estimated growth rate (m MAX ) of 3.62 1/d. The calculated TOC removal was in good agreement with the experimental results. The two-phase model was also able to predict the TN removal of the system. The modeling of the coupling CWHPO/RBCs process could be a useful guide in order to achieve a cost-effective process leading to optimum C/N composition of the treated effluent and resulting in better overall removal efficiency. ã 2016 Elsevier Ltd. All rights reserved. 1. Introduction Biological treatments are usually the most attractive technolo- gies for wastewater treatment in terms of economic costs and environmental impacts. However, the presence of non-biodegrad- able and/or toxic pollutants, accompanied with the restricted capacity of these processes to treat only diluted streams, have limited their technical application [1]. In these cases, a suitable alternative is the use of advanced oxidation technologies, such as Catalytic Wet Hydrogen Peroxide Oxidation (CWHPO), widely recognized as highly efficient treatment for the abatement of recalcitrant pollutants in wastewaters [2]. Thus, an interesting approach is to apply CWHPO as pre-treatment of biological processes to convert the hazardous and persistent organic pollutants into more biodegradable compounds, which will be amenable to be degraded by biological processes with a consider- ably lower cost [1,3,4]. Pesticide-containing wastewaters are a typical example of wastewaters with biologically recalcitrant and toxic compounds. Their critical effect on the environment and human health makes necessary the elimination of these com- pounds by efficient and environmental-friendly technologies [5]. The monitoring of these compounds over the last 20 years has demonstrated some chronic effects such as carcinogenesis, neurotoxicity, sterility and cell development effects, particularly in the early stages of life [6–8]. These substances are contained in wastewaters of agrochemical plants dedicated to the manufacture of pesticides and also some wastewaters coming from the food manufacturing. The treatment of a non-biodegradable wastewater stream coming from an agrochemical industry by coupling of CWHPO and RBCs has been preliminary studied in literature [9]. The as-received wastewater was characterized by TOC and COD loadings of 9 and * Corresponding author. E-mail address: raul.molina@urjc.es (R. Molina). http://dx.doi.org/10.1016/j.jece.2016.04.007 2213-3437/ ã 2016 Elsevier Ltd. All rights reserved. Journal of Environmental Chemical Engineering 4 (2016) 2313–2321 Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering journal homepage: www.else vie r.com/locat e/jece