Recent progress using membrane aerated biofilm reactors for wastewater treatment

Abstract

The membrane biofilm reactor (MBfR), which is based on the counter diffusion of the electron donors and acceptors into the biofilm, represents a novel technology for wastewater treatment. When process air or oxygen is supplied, the MBfR is known as the membrane aerated biofilm reactor (MABR), which has high oxygen transfer rate and efficiency, promoting microbial growth and activity within the biofilm. Over the past few decades, lab-scale studies have helped researchers and practitioners understand the relevance of influencing factors and biological transformations in MABRs. In recent years, pilot- to full-scale installations are increasing along with process modeling. The resulting accumulated knowledge has greatly improved understanding of the counter-diffusional biological process, with new challenges and opportunities arising. Therefore, it is crucial to provide new insights by conducting this review. This paper reviews wastewater treatment advancements using MABR technology, including design and operational considerations, microbial community ecology, and process modeling. Treatment performance of pilot- to full-scale MABRs for process intensification in existing facilities is assessed. This paper also reviews other emerging applications of MABRs, including sulfur recovery, industrial wastewater, and xenobiotics bioremediation, space-based wastewater treatment, and autotrophic nitrogen removal. In conclusion, commercial applications demonstrate that MABR technology is beneficial for pollutants (COD, N, P, xenobiotics) removal, resource recovery (e.g., sulfur), and N2O mitigation. Further research is needed to increase packing density while retaining efficient external mass transfer, understand the microbial interactions occurring, address existing assumptions to improve process modeling and control, and optimize the operational conditions with site-specific considerations.

The Effects of Low Oxidation-Reduction Potential on the Performance of Full-Scale Hybrid Membrane-Aerated Biofilm Reactors

“…Terada et al, 2006 found in a membrane biofilm reactor fed with hydrogen gas that SRBs did not grow well while the ORP in the biofilm was high (0 mV), but they observed that 50 % of the sulfate was converted by SRBs when ORP was decreased to − 300 mV. More recently, MABR has been identified as an efficient technology to recover sulfur via sulfide-oxidizing bacteria, as the counter-diffusional characteristics of the biofilm allow for more efficient oxygen control [75,27].…”

Low strength and COD/N wastewater treatment via controlled nitrification by a membrane aerated biofilm, partial denitrification by activated sludge, and anaerobic ammonia oxidation by granular sludge

“…However, AOB and NOB can be preferentially enriched as a biofilm on an aerated membrane surface due to the high dissolved oxygen concentration near the outer membrane surface from bubble-free membrane aeration with a high oxygen transfer capability. 12 The membrane aerated biofilm (MAB), initially developed as an autotrophic biofilm with mainly AOB and NOB for nitrification, was then developed as a stratified biofilm with inner autotrophic bacteria and outer heterotrophic bacteria for simultaneous carbon and nitrogen removal. 13 Benefiting from aeration flexibility via adjusting pressure or flowrate, MAB can achieve nitrification only or simultaneous nitrification and denitrification.…”

Startup and initial operation of an MLE-MABR treating municipal wastewater

“…A fundamental characteristic of MABRs is the counter-diffusional biofilm process where air is supplied via a hollow-fiber gas-permeable membrane and oxygen diffuses throughout the biofilm while the substrate from the bulk liquid diffuses into the biofilm (Nerenberg 2016). The technology was first commercialized in 2015 (Uri-Carreño et al 2018) and both pilot and full-scale installations have been increasing recently, contributing to the understanding of its challenges and opportunities (He et al 2021).…”

“…Temperature affects diffusivity constants, oxygen solubility, membrane permeability, biomass growth rate and, consequently the biofilm thickness. Excessive biofilm thickness raises concern for mass transfer and membrane clogging, which is a frequent operational problem (He et al 2021). Another factor that affects biofilm characteristics is the availability of biodegradable soluble carbon as it promotes the potentially excessive growth of heterotrophs, which may be detrimental to the nitrification process.…”

“…On one hand, excessive scouring promotes excessive biofilm detachment and consequent biomass washout. On the other, ineffective scouring encourages membrane bridging issues with the associated decrease of biofilm surface area (He et al 2021).…”