Search Results (8)

The membrane-aerated biofilm reactor (MABR) is an emerging technology for the biological treatment of wastewaters. It can achieve simultaneous nitrification and denitrification due to anoxic liquid conditions. The counter diffusion of oxygen and nutrients in the biofilm allows for aerobic and anoxic layers, providing conditions where the formation, accumulation and consumption of nitrous oxide can all occur. The microbial processes involved in the production and consumption of N₂O are complex, and, due to the innovative nature of the MABR, understanding the influence of operational factors helps to minimise N₂O emission. Using a lab-scale 20L MABR system, an investigation was carried out to determine the influence of operational factors on the emission of nitrous oxide from the reactor. A direct link between the nitrous oxide emissions and bulk liquid conditions could not be established with only limited statistical correlation between them. It was found that under both steady loading rates and transient conditions, the emission of nitrous oxide was most influenced by the air flow rate through the membranes. The majority of N₂O emissions occurred via the membrane off-gas and not through the liquid. N₂O flux through the membrane was influenced not only by the accumulation of N₂O in the biofilm side but also by the gas residence time on the lumen side. Therefore, minimising the air flow rate is an effective strategy to mitigate nitrous oxide emissions from the MABR. Full article

Lumen pressure is of crucial importance to achieve simultaneous nitrification and denitrification (SND) in the membrane aerated biofilm reactor (MABR); so, in this study, a laboratory-scale MABR was operated under different lumen pressures (7 kPa, 10 kPa, 13 kPa, and 16 kPa) successively to verify its impact on nitrogen removal. The results showed that NH₄⁺-N oxidation was deficient under 7 kPa due to inadequate oxygen supply, while denitrification was depressed under 16 kPa. Total nitrogen removal efficiency was similar under 10 kPa and 13 kPa (around 78.9%), much higher than that under 7 kPa and 16 kPa (approximately 50%). The biomass density (22.35 g/m²) and biofilm thickness (500.3 µm) were the highest under 13 kPa, and EPS was increasingly secreted along with the increase in lumen pressure. The relative abundance of Nitrospirae was highest under 16 kPa (3.53%), indicating a higher lumen pressure could promote nitrifiers. The denitrifying-related microbes, such as β-proteobacteria, α-proteobacteria and ε-proteobacteria, showed an increasing and then decreasing pattern along with lumen pressure increase, and were enriched at 10 kPa. The results could draw the conclusion that SND could be achieved at moderate lumen pressure, i.e., 10 kPa and 13 kPa in this study. Full article

Nutrient removal in conventional wastewater treatment systems is expensive due to the high aeration costs. An alternative method for effective and sustainable nitrogen removal in wastewater treatment is anaerobic ammonium oxidation (Anammox) implemented with other innovative technologies, such as membrane-aerated biofilm reactors (MABRs). A major challenge associated with the Anammox process is effective control of nitrite-oxidizing bacteria (NOB). High temperature operation in wastewater treatment systems can promote Anammox bacterial growth and inhibit NOB activity. This research aims to investigate the feasibility of integrating Anammox processes with a lab-scale MABR and to examine the effects of high temperature aeration supplied to MABR systems on Anammox bacterial growth and NOB suppression. Experimental results indicate that the membrane’s air permeability was a critical parameter for the successful operation of Anammox-integrated MABR systems due to its influence on the system’s dissolved oxygen concentration (0.41 ± 0.39 mg O₂/L). The ammonia removal by AOB and Anammox bacteria was determined to be 7.53 mg N/L·d (76.5%) and 2.12 mg N/L·d (23.5%), respectively. High temperature aeration in MABRs with the Anammox process shows a promising potential for improving energy consumption and sustainable nitrogen removal in wastewater treatment systems. Full article

Microporous membranes such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) often exhibit suboptimal hydrophilicity and microbial adhesion, which impede effective nitrogen removal in membrane-aerated biofilm reactors (MABRs), particularly during initial operational phases. To address this issue, the present study introduced acrylic acid (AA) following plasma treatment (P) to enhance membrane performance, thereby engineering a novel composite material optimized for MABR applications. Four MABRs—Reactor with pristine PVDF membrane (R-PVDF), Reactor with composite PVDF membrane (R-PVDF-P-AA), Reactor with pristine PTFE membrane (R-PTFE), and Reactor with composite PTFE membrane (R-PTFE-P-AA)—were evaluated. The modified membranes displayed enhanced roughness and hydrophilicity, which improved biocompatibility and variably increased the oxygen transfer efficiency. Notably, the R-PVDF-P-AA configuration showed a significant enhancement in the removal rates of NH₄⁺-N and total nitrogen (TN), achieving 78.5% and 61.3%, respectively, which was markedly higher than those observed with the original membranes. In contrast, the modified R-PTFE-P-AA exhibited lower removal efficiencies, with NH₄⁺-N and TN reductions of approximately 60.0% and 49.5%. Detailed microbial community analysis revealed that the R-PVDF-P-AA membrane supported robust commensalism between ammonia-oxidizing and denitrifying bacteria, underpinning the improved performance. These findings highlight the critical role of surface chemistry and microbial ecology in optimizing the function of MABRs. Full article

In this study, a laboratory-scale membrane aerated biofilm reactor system was operated successively through four phases with different C/N ratios (7, 5, 3, and 1) for 15 days each to investigate the C/N ratio’s effect on the COD and nitrogen removal. The COD and NH₄⁺-N removal efficiencies were slightly affected; however, NO₃⁻-N accumulated in the C/N = 1 phase, and slight NO₂⁻-N accumulation was observed in the C/N = 7 phase, leading to lower total nitrogen (TN) removal in the two phases. The TN removal efficiency reached the highest in the C/N = 5 phase at around 70%, and the TN concentration was reduced to 12.3 mg/L on average. Biomass and biofilm thickness had a positive correlation with C/N ratios. The C/N ratio affected not only the generation of extracellular polymeric substances but also their chemical composition. Microbial analysis revealed that a C/N ratio of 5 was the most suitable for both nitrifying and denitrifying bacteria, and a higher C/N ratio favored aerobic denitrifying microbes. Full article

As a new type of biological treatment process, membrane aerated biofilm reactors (MABRs), which have received extensive attention and research in recent years, could reduce energy consumption by 70% compared to the traditional activated sludge process. The MABR system uses bubble-free aeration membrane material as the carrier, the counter-diffusion mechanism of oxygen and pollutants enables ammonium oxidizing bacteria (AOB) and nitrate oxidizing bacteria (NOB) to adhere to the membrane surface so that simultaneous nitrification and denitrification (SND) can occur to achieve simultaneous nitrogen and carbon removal. Currently, MABR technology has been successfully applied to the treatment of municipal sewage, various industrial wastewater, pharmaceutical, high salinity, high ammonia, aquaculture wastewater, landfill leachate and black and odorous water bodies in rivers. Many laboratory experiments and pilot-scale MABR reactors have been used to study the performance of membrane materials, the mechanism of pollutant removal and the effects of different factors on the system. However, the performance of MABR is affected by factors such as dissolved oxygen (DO), pH, C/N, biofilm thickness, hydraulic retention time (HRT), temperature, etc., which limits large-scale promotion. Therefore, membrane materials, membrane modules, biofilm, application of MABR technology, influencing factors of MABR system performance, and limitations and perspectives of MABR are reviewed in this paper, and we expect to provide valuable information. Full article

Sustainability has been a concern of survival for future long-term manned space missions. Therefore, the wastewater generated by the crew members, containing urine and hygiene wastewater, should be treated with appropriate biological processes to promote recycling efficiency. In this study, we developed a membrane-aerated biofilm reactor (MABR) that could achieve up to 96% total organic carbon (TOC) removal efficiency and up to 82% denitrification efficiency for an influent with 370–390 mg/L TOC and 500–600 mg/L total nitrogen (TN) without additional carbon source or sludge discharge. The nitrogen removal rate was about 100 mg N L⁻¹ d⁻¹. Metagenomic analysis indicated the presence of a variety of nitrifying, denitrifying, and anammox bacteria in the microbial community and existence of functional genes in nitrification, denitrification, and anammox pathways. Full article

The concept of thermophilic membrane-aerated biofilm reactor (ThMABR) is studied by modeling. This concept combines the advantages and overcomes the disadvantages of conventional MABR and thermophilic aerobic biological treatment and has great potential to develop a new type of ultra-compact, highly efficient bioreactor for high-strength wastewater and waste gas treatments. Mathematical modeling was conducted to investigate the impact of temperature (mesophilic vs. thermophilic) and oxygen partial pressure on oxygen and substrate concentration profiles, membrane–biofilm interfacial oxygen concentration, oxygen penetration distance, and oxygen and substrate fluxes into biofilms. The general trend of oxygen transfer and substrate flux into biofilm between ThAnMBR and MMABR was verified by the experimental results in the literature. The results from modeling studies indicate that the ThMABR has significant advantages over the conventional mesophilic MABR in terms of improved oxygen and pollutant flux into biofilms and biodegradation rates, and an optimal biofilm thickness exists for maximum oxygen and substrate fluxes into the biofilm. Full article