Optimization of operating parameters for biogas production using two-phase bench-scale anaerobic digestion of slaughterhouse wastewater: Focus on methanogenic step

Abstract

The objective of the present study was an optimization of operating parameters and the performance of the methanogenesis reactor in phased anaerobic digestion (AD) of slaughterhouse wastewater at 37.5°C. Accordingly, the feedstock of the methanogenic reactor was effluent from the hydrolytic-acidogenic reactor operating at HRT of 3-days and OLR of 1789 mg/L. The methanogenesis phase was also investigated at different hydraulic retention time (HRT) values ranging from 12 to 3 days at 3-day intervals, and organic loading rates (OLR) of 149, 199, 298, and 596 mg of COD/L. The methanogenesis reactor effluent concentrations of TN, TP, PO4− 3, SO4− 2, and S2− 2 were ranging between 424–464, 83–117, 63–86, 130–197, and 0.98–1.02 mg/L, respectively. The removal efficiencies of TN and TP were vary from 10–17% to 17–21%, respectively. The average biogas production was 125 ± 16, 150 ± 10, 185 ± 4, and 154 ± 17 mL at HRT of 12, 9, 6, and 3 days, respectively. Methane quality (%) and yield (mg/L of COD) were 55–67% and 0.02–0.03, respectively. Furthermore, the average stability indicator parameter values of (total volatile fatty acid (TVFA) = 520 ± 19 mg/L, total alkalinity (TotA) = 1424 ± 10 mg/L, TVFA:TotA. Ratio = 0.36, salinity = 1172 mg/L, pH = 6.92) and performance indicator parameters removal efficiency (RE) for (chemical oxygen demand (COD) = 81%, volatile solid (VS) RE = 95%, biogas production = 185 ± 4 mL, methane yield = 0.03 per mg COD consumed) were achieved at HRT of 6 days and OLR of 298 mg of COD/L. Low removal efficiencies of TP and TN at all HRT/OLR were observed for the methanogenic reactor signifying further treatment system. Graphical Abstract

Optimization of Operating Parameters for Two-Phase Anaerobic Digestion Treating Slaughterhouse Wastewater for Biogas Production: Focus on Hydrolytic–Acidogenic Phase

“…Mulu and Ayenew [10], Ren et al [54], and Worku and Leta [1] reported the COD values of the slaughterhouse as 4752.66 ± 1156.27 mg/L and 6942.59 ± 152.98-7079.69 ± 226.89 mg/L, respectively. Furthermore, slaughterhouses and meat-processing facilities produce a huge volume of wastewater with organic matter measured as COD between 500 and 15,900 mg/L [52], TVFA between 435 and 1197 mg/L [55], and NH 4 + -N between 186 and 6407 mg/L [1,46]. This high concentration of organic matter necessitates a greater amount of oxygen to be oxidized into carbon dioxide and water, which may contribute to an increase in the COD and BOD of the receiving water body [56].…”

Microalgae and co-culture for polishing pollutants of anaerobically treated agro-processing industry wastewater: the case of slaughterhouse

“…In developing countries, more than ninety percent of the agro-processing industries discharge partially treated or untreated effluents recklessly into the environment. The effluents from the agro-processing industries as well as anaerobic digestion (AD) effluents are known for their high organic matter, nutrients, and other pollutants that are unsafe to the receiving water bodies or environment (Zemene Worku and Seyom Leta 2017 ; Ashekuzzaman et al 2019 ; Bustillo-Lecompte and Mehrvar 2015 ; Hailu et al 2020 ; Yirgu et al 2020 ; K. Praveen et al 2018 ; Leta et al 2003 ), directing post-treatment process requirement to minimize or remove organic matters as organic and inorganic forms of phosphorus and nitrogen of the effluents (De Nardi et al 2011 ; Chevalier et al 2000 ; Dawana and Kassa 2020 ; Tsegaye and Leta 2022 ). If directly released, it results in eutrophication of the receiving water bodies and other environmental risks associated with greenhouse gas emissions from ammonia volatilization, groundwater nitrogen contamination, or pollution, and also affects human health via the food chain (Akar and Tunali 2005 ; Carey and Migliaccio 2009 ; Fornarelli, Bahri, and Moheimani 2017 ).…”