Synergising Anaerobic Membrane Bioreactor and Microbial Electrochemical Cell in Anaerobic Electrochemical Membrane Bioreactor for Low-Strength Wastewater Treatment

Abstract

Water scarcity has become pervasive in numerous regions worldwide over the past few decades. The exacerbation of water scarcity is expected to increase due to the compounding factors of climate change and the discharge of inadequately treated wastewater into water bodies. A contemporary perspective recognises wastewater, including low-strength wastewater, as a valuable resource for water, nutrients, and renewable energy. Consequently, there is an urgent need to develop sustainable and effective technologies for wastewater treatment. This thesis investigated the efficacy of an anaerobic membrane bioreactor (AnMBR) utilising a submerged hollow fibre membrane (HFM) module to treat low-strength wastewater, emphasising fouling behaviour across different organic loading rates (OLRs). Furthermore, this thesis delved into examining the efficiency of single-chamber microbial electrolysis cells (MEC) as a potential technology to be integrated with an AnMBR, focusing on the influence of the applied electric field on organic and nutrient removal, biogas quality, and shifts in microbial communities. Finally, this thesis explored the viability of integrating dual-function nickel-HFM (Ni-HFM) into a hybrid AnMBR and MEC system, termed an anaerobic electrochemical membrane bioreactor (AnEMBR), for low-strength wastewater treatment. The results of the AnMBR study demonstrated a significant impact of OLRs on the specific production rates of Extracellular Polymeric Substances (EPS) and Soluble Microbial Products (SMP), affecting fouling behaviour at different OLRs. The MEC study showed up to 9.5% enhancement in organic removal efficiency, 13.3-fold increase in ion and nutrient removal, and 8.4% rise in methane content in biogas compared to conventional anaerobic digestion at 0.9 V. A slight reduction in overall treatment efficiency occurred at 1.2 V due to severe plasmatorrhexis, which potentially disrupting microorganism metabolism activities in the system. Finally, the study on AnEMBR showcased its viability as a promising technology for treating low-strength wastewater with up to 9% improvement in organic removal, 60% increase in membrane filtration efficiency, 12.4% - 16.7% enhancement in ions and nutrient removal, and 8% increase in methane content in biogas as compared to non-electrochemically induced system (AnMBR). The findings derived from these investigations provide crucial insights into the integration of AnMBR and MEC into AnEMBR for the treatment of low-strength wastewater.