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Reactor reconfiguration for enhanced performance of a down-flow expanded granular bed reactor (Degbr) for poultry slaughterhouse treatment
The poultry industry is one of the largest industries in the South African agricultural sector. To sustain their various operations, this industry utilises a large quantity of potable water to process slaughtered birds in order to satisfy hygiene and sanitation requirements in processing facilities. Thus, the consumption of potable water during poultry slaughterhouse operations results in the production of high-strength poultry slaughterhouse wastewater (PSW), which is laden with a variety of pollutants, including fats, oil and grease (FOG), carcass debris, feathers and organic matter, including proteins, that should be removed from the wastewater, or at least reduced in concentration, prior to the PSW being discharged into the environment. This is to avoid and/or minimise levies and non-compliance penalties from monitoring institutions in charge of controlling the quality of effluents in the area from which the PSW was collected for this study. Furthermore, the option of treating and recycling the PSW to address the current issue of water scarcity in the Western Cape (South Africa), and to minimise possible harmful effects on the environment, will reduce the overreliance on slaughterhouses in the region on potable/drinking water, thus also lessening running costs associated with water procurement for operations. Various technologies, involving physical, chemical or biological processes, have been evaluated for the treatment of PSW, with this study focusing on anaerobic treatment (part of the biological treatment) of PSW, using a high-rate anaerobic bioreactor system (HRABs), which provides for low production of sludge, the production of biogas as a source of energy and the provision of high performance in terms of organic matter removal. Moreover, HRABs are cheaper, when compared to other aerobic treatment technologies. However, numerous potential challenges were encountered when using HRABs, such as low production of biogas due to gas entrapment, head losses across the granular bed, sludge washout in upflow HRABs, uneven wastewater distribution, and thus poor dispersion of the organic matter, which impacts on the adequacy of treatment, poor release of toxic substances contained in the entrapped biogas (NH3 or H2S), clogging of the underdrain system for down-flow HRABs, or the formation of dead zones within the granular bed, resulting in short-circuiting.