Long-term performance evaluation of a membrane bioreactor for slaughterhouse wastewater reclamation and reuse

Abstract

Increasing water scarcity is highlighted as a major threat to human development. Food processing industry, which is a traditional pillar of many economies worldwide, is an important water consumer facing increasing pressure towards new supply strategies. The slaughtering industry, producing large volumes of wastewater characterized by a high content in organic matter and pathogens, stands as one of the most promising and challenging sectors for the implementation of water reclamation technologies. In this sense, membrane bioreactors (MBR) are an emerging strategy for slaughterhouse wastewater (SWW) treatment to achieve treated water quality suitable for water reuse within the food industry. In this study, the performance of a pilot MBR treating SWW has been investigated for 3 different periods accounting for over 600 d of operation, from a singular approach evaluating both technical and regulatory factors determining the technology applicability in an industrial environment for water reclamation and reuse purposes. For the studied parameters, the bioreactor showed an efficient performance at a hydraulic retention time (HRT) above 1.5 d, with removal efficiencies higher than 95 % and 99 % for chemical oxygen demand and ammonium, respectively. At HRT under 1.5 d, the MBR performance was compromised, showing imbalanced microbial populations, partial nitrification driving to nitrite accumulation and increased membrane fouling rate. Regarding the quality of the MBR permeate, the HRT of 2 d was the only one fitting the required parameters for water reuse as process and cleaning water within the food industry, according to the Spanish water reuse regulation in force (RD 1085/2024).