Excess bio-sludge and contamination load minimisation: A comparative study on conventional activated sludge (CAS) and integrated treatment of CAS–AnMBR for environmental optimisation

ABSTRACT Slaughterhouse wastewater (SWW) contains high levels of biodegradable organic compounds, posing significant environmental hazards. The wastewater often exceeds regulatory discharge limits for contaminants, exacerbating eutrophication. Thus, biological treatment methods like activated sludge and anaerobic digestion remain preferable over physical or chemical processes for handling this wastewater. This study evaluated an integrated conventional activated sludge (CAS) and anaerobic membrane bioreactor (AnMBR) system for SWW to achieve high treatment efficiency while minimising excess sludge production. The wastewater was initially treated by a CAS system operated at a food-to-microorganism ratio of 0.2; the effluent then underwent anaerobic digestion in the AnMBR with an organic loading rate of 0.5 g COD/L/h. The integrated system achieved over 90% removal for COD and suspended solids and over 80% for nitrogen and phosphorus removal. It also reduced excess sludge by 30% compared to standalone CAS. Estimated biogas production was 0.6 m3/h with 50–70% methane content. The high pollution removal, sludge minimisation, and renewable energy generation indicate that the integrated CAS–AnMBR system is a promising sustainable SWW treatment approach. The positive initial results warrant further examinations of methane yields, cost-effectiveness, and optimisation.