Biofilm Formation and Control in Membrane Aerated Biofilm Reactor Systems for Wastewater Treatment

Membrane Aerated Biofilm Reactors (MABRs) have emerged as a promising alternative to conventional activated sludge systems for wastewater treatment, with potential advantages related to oxygen transfer efficiency and process intensification. By coupling gas-permeable membranes with biofilm-based treatment, MABRs enable simultaneous nitrification and denitrification within a single reactor, reducing aeration energy consumption by up to 70%. The performance of MABRs is fundamentally governed by the formation and structure of the attached biofilm, which serves as the core zone for microbial activity. Critical biofilm properties, including thickness, density, porosity, and microbial stratification, determine oxygen and substrate diffusion, reaction kinetics, and nutrient removal efficiency; however, excessive growth can result in oxygen limitation, membrane fouling, and performance deterioration. Despite extensive reviews on MABR principles, applications, and performance, there is a limited focused review on biofilm formation dynamics, structural architecture, microbial stratification, and their influence on mass transfer, nutrient removal, and targeted control strategies, all points that are examined in this review, highlighting their role in optimizing treatment performance, energy efficiency, and system stability. Identified key research gaps includes the need for predictive models linking biofilm heterogeneity to performance and the development of fouling-resistant, high-permeability membranes, to guide future advancements in sustainable wastewater treatment.