A comprehensive review of slaughterhouse wastewater treatment and concomitant resource recovery

Abstract

Due to the ever-rising demand for meat, the number of slaughterhouses and associated wastewater generation have significantly increased in the recent past. Processes such as lairage, sticking, washing, hide storage, and rendering require a huge volume of water. Tentatively, 82%-98% of the entire water consumed (~1100L of freshwater/adult ruminant) for slaughtering and ancillary processes gets converted as wastewater. The typical ranges of the parameters that characterize slaughterhouse wastewater (SWW) are: pH: 6.2-7.9, TSS: 14,000-19,000mg/L, TDS: 1200-350,000mg/L, FOG: 12,000-37,000mg/L, COD: 4200-120,000mg/L, BOD: 1800-49,000mg/L, TKN: 120-1105mg/L, TP: 3-305mg/L. Large variations and a severely high concentration of nutrients and FOG complicate the SWW treatment and recovery processes. Formerly, a combination of pretreatment (drum screen, settler, coagulation and flocculation) followed by physical treatment (dissolved air floatation) or biological treatment (upflow anaerobic sludge blanket reactor, activated sludge process) was practiced to treat SWW. But the process requires a long start-up, acclimatization period, and large area, yet lacks efficacy, especially in removing TP. So, in recent times, advanced pretreatment by electrocoagulation followed by secondary treatment using an anaerobic baffled reactor or anaerobic sequencing batch reactor is practiced. Further, the treated effluent is subjected to membrane bioreactor and reverse osmosis processes. Such a treatment strategy could lead to 90% efficiency or more. The treatment cost is approximately 0.12 USD/KL, which can be further lowered by facilitating energy recovery as methane-rich biogas from the anaerobic process (250mLCH4 gVS−1 SWW). The treated wastewater can be rationally reused to partially compensate for the water demand for in-situ processes such as scalding, chilling, dehairing, slaughter-line rind treatment, carcass dressing, cutting, deboning, and fat plant. © 2024 Elsevier Inc. All rights are reserved including those for text and data mining AI training and similar technologies.