Treatment of poultry slaughterhouse wastewater using a down-flow expanded granular bed reactor M. Njoya a , M. Basitere b and S. K. O. Ntwampe b, * a Bioresource Engineering Research Group (BioERG), Department of Biotechnology, Cape Peninsula University of Technology, Cape Town, South Africa b Department of Chemical Engineering, Cape Peninsula University of Technology, Cape Town, South Africa *Corresponding author. E-mail: ntwampes@cput.ac.za Abstract This study evaluated the performance of a novel high rate anaerobic bioreactor system for the treatment of poul- try slaughterhouse wastewater (PSW). The new system consisted of a granule-based technology operated in a down-flow configuration, with the assistance of medium-sized pumice stones used as packing materials for the retention of the anaerobic granules, to avoid challenges associated with the use of the three-phase separator of up-flow systems and the washout of the anaerobic biomass. Furthermore, a recycling stream was applied to the system to improve the mixing inside the Down-flow Expanded Granular Bed Reactor (DEGBR), i.e. the influent distribution to the granular biomass, and the implementation of intermittent fluidization when required to alleviate the effects of pressure drop in such systems. The DEGBR was operated under mesophilic conditions (30–35 °C) and achieved total chemical oxygen demand (tCOD), five-day biological oxygen demand and total sus- pended solids average removal percentages .95%, and a fats, oils and grease average removal percentage of 93.67% + 4.51, for an organic loading rate varying between 1.1 to 38.9 gCOD/L.day. Key words: anaerobic granule-based technology, chemical oxygen demand, down-flow expanded granular bed reactor, high rate anaerobic bioreactor system, poultry slaughterhouse wastewater treatment INTRODUCTION The efficacy of anaerobic digestion for the secondary treatment of low to high strength wastewater has been highly acclaimed since the development of high rate anaerobic bioreactor systems (HRABs) (Metcalf & Eddy 2003; Chernicharo 2007; Henze et al. 2008). HRABs heavily rely on the develop- ment of anaerobic granular sludge and improved biomass retention (Hulschoff Pol et al. 2004), which culminates in effective solid retention time (SRT) and suitable hydraulic retention time (HRT) (Alphenaar 1994; Henze et al. 2008). This results in enhanced wastewater treatment perform- ance in terms of effluent quality and processing time. In comparison to the aerobic treatment of wastewater, the anaerobic treatment has numerous advantages including a reduced plant footprint (Henze et al. 2008; Debik & Coskun 2009); less energy requirement, which is usually associated with the supply of dissolved oxygen in aerobic systems (Chernicharo 2007; Henze et al. 2008); low initial and operating costs (Debik & Coskun 2009); less sludge generation, which does not require further treatment but can be used for inoculating another biodigester and therefore reduce the start-up time (Henze et al. 2008); and biogas production, whose methane content represents an alternative source of energy (Chavez et al. 2005). Following the success of the up-flow anaerobic sludge blanket (UASB) (Lettinga & Hulschoff Pol 1991; Hulschoff Pol et al. 2004), various HRABs, such as the expanded granular sludge bed (EGSB) reactor (Kato et al. 1994; Basitere et al. © IWA Publishing 2019 Water Practice & Technology Vol 14 No 3 549 doi: 10.2166/wpt.2019.039 Downloaded from https://iwaponline.com/wpt/article-pdf/14/3/549/605311/wpt0140549.pdf by guest on 25 November 2019