Anaerobic Treatment Performance of Co-Digested Slaughterhouse Waste

Abstract

Most underdeveloped countries struggle to find long-term solutions to safe and economical treatment and disposal of agricultural wastes. Slaughterhouse wastewater (SHWW) has a significant potential for biomethane (bioCH4) yield when anaerobically treated. The procedure, however, is prone to failure. As a result, anaerobic codigestion (ACoD) is used to boost the efficacy of SHWW anaerobic monodigestion (AMoD). The main objective of this study was to assess the anaerobic treatment performance of SHWW co-digested with sugar press mud (SPM). The study used a biochemical methane potential (BMP) test to assess the bioCH4 yield of SHWW codigested with SPM at varied mixing ratios. SPM boosted CH4 yield and VS removal by 27% and 67%, respectively, at an optimum mixing ratio of 20%SHWW: 80%SPM. Furthermore, the influence of ACoD of SHWW with SPM on organic removal efficiency at various hydraulic retention times (HRTs) was investigated semi-continuously in lab-scale continuous stirred tank reactors (CSTRs) under mesophilic (37.0 ± 1.0 °C) conditions. At the optimal 15 days (d) HRT, ACoD increased CH4 yield and VS removal by 69.1% and 62.4%, respectively. Further, the addition of SPM improved the stability of the AD process, as evidenced by a drop in ammonium nitrogen (NH4+-N) concentration. A modified Gompertz model was also used to determine the kinetics of organic degradation of SHWW and SPM. The study's kinetic analysis revealed that the rate of CH4 yield increased by about 46% while the lag time was greatly reduced by approximately 87%. Therefore, use of SPM as a co-substrate improved the treatment performance of SHWW and recovery of bioCH4. This would also help to increase the use of renewable energy sources in electricity generation, cutting greenhouse gas (GHG) emissions. The mesophilic temperature (37.0 ± 1.0 °C) was maintained throughout the study; therefore, it is recommended that investigations under thermophilic circumstances should be conducted in the future to investigate the effect of temperature on AD process stability.