Process characteristics and energy self-sufficient operation of a low-fouling anaerobic dynamic membrane bioreactor for up-concentrated municipal wastewater treatment

Anaerobic membrane bioreactors for municipal wastewater: Progress in resource and energy recovery improvement approaches

Anaerobic membrane bioreactor (AnMBR) offer promise in municipal wastewater treatment, with potential benefits including high-quality effluent, energy recovery, sludge reduction, and mitigating greenhouse gas emissions. However, AnMBR face hurdles like membrane fouling, low energy recovery, etc. In light of net-zero carbon target and circular economy strategy, this work sought to evaluate novel AnMBR configurations, focusing on performance, fouling mitigation, net-energy generation, and nutrients-enhancing integrated configurations, such as forward osmosis (FO), membrane distillation (MD), bioelectrochemical systems (BES), membrane photobioreactor (MPBR), and partial nitrification-anammox (PN/A). In addition, we highlight the essential role of AnMBR in advancing the circular economy and propose ideas for the water-energy-climate nexus. While AnMBR has made significant progress, challenges, such as fouling and cost-effectiveness persist. Overall, the use of novel configurations and energy recovery strategies can further improve the sustainability and efficiency of AnMBR systems, making them a promising technology for future sustainable municipal wastewater treatment.

Synergistic effects of biochar addition and filtration mode optimization on mitigating membrane fouling in high-solid anaerobic membrane bioreactors

In this study, a high-solid anaerobic membrane bioreactor was established for treating food waste, and membrane fouling rates were regulated through multivariate modulation. The anaerobic membrane bioreactor operated stably at a high organic loading rate of 28.75 gCOD/L/d achieved a methane production rate of 8.03 ± 0.61 L/L/d. Experimental findings revealed that the most effective control of membrane fouling was achieved at a filtration- relaxation ratio (F/R) of 10/90 s. This indicates that a higher relaxation frequency provided improved the mitigation of membrane fouling. Compared with single F/R modulation, the combined modulation of biochar and F/R provided enhanced control over membrane fouling. Moreover, the addition of biochar altered the sludge properties of the reactor, thereby preventing the formation of a dense cake layer. Additionally, biochar enhanced the sheer force of the fluid on the membrane surface and facilitated the separation of pollutants during the relaxation stage, thereby contributing to improved control of membrane fouling.

Carbon-negative and high-rate nutrient recovery from municipal wastewater using mixotrophic Scenedesmus acuminatus

The efficiency of mixotrophic microalgae in enhancing the recovery of waste nutrients has been well established; however, the recovery rate is crucial in meeting the needs of field applications. This study evaluated the impact of media characteristics on nutrient recovery under mixotrophic conditions. The mixotrophic N recovery rate with S. acuminatus in modified BG-11 reached 2.59 mg L-1h-1. A mixotrophic growth optimization strategy was applied to achieve a high-rate nutrient recovery from municipal wastewater treatment plant effluents. The contribution of waste chemical oxygen demand (COD) to nutrient recovery was assessed using secondary effluent (SE) under heterotrophy. The results highlighted a significant increase in total nitrogen (TN) and total phosphorus (TP) recovery rates when glucose was supplied, indicating the additional carbon requirements for efficient nutrient recovery. The TN and TP recovery rates under mixotrophic conditions with the addition of trace metals and high cell density were enhanced by 91.94% and 92.53%, respectively, resulting in recovery rates of 3.43 mg L-1h-1 and 0.30 mg L-1h-1. The same conditions were used for nutrient recovery from primary effluent (PE), and the results were more satisfactory as the TN and TP recovery rates reached 4.79 and 0.55 mg L-1h-1, respectively. Additionally, the study estimated the carbon footprints (C-footprints) and areal footprints of mixotrophy-based nitrogen recovery. The findings revealed carbon footprints and areal footprints of -15.93 ± 4.57 tCO2e t-1 N recovery and 0.53 ± 0.19 m3 m-2d-1 wastewater, respectively. This high-rate nutrient recovery, achieved under a carbon-negative (C-negative) budget through mixotrophy, presents a novel strategy for efficiently recovering resources from municipal wastewater, thus facilitating resource recycling and ensuring environmental sustainability.

Bioelectrochemical anaerobic membrane bioreactor enables high methane production from methanolic wastewater: Roles of microbial ecology and microstructural integrity of anaerobic biomass

The disintegration of anaerobic sludge and blockage of membrane pores has impeded the practical application of anaerobic membrane bioreactor (AnMBR) in treating methanolic wastewater. In this study, bioelectrochemical system (BES) was integrated into AnMBR to alleviate sludge dispersion and membrane fouling as well as enhance bioconversion of methanol. Bioelectrochemical regulation effect induced by BES enhanced methane production rate from 4.94 ± 0.52 to 5.39 ± 0.37 L/Lreactor/d by accelerating the enrichment of electroactive microorganisms and the agglomeration of anaerobic sludge via the adhesive and chemical bonding force. 16 S rRNA gene high-throughput sequencing demonstrated that bioelectrochemical stimulation had modified the metabolic pathways by regulating the key functional microbial communities. Methanogenesis via the common methylotrophic Methanomethylovorans was partially substituted by the hydrogenotrophic Candidatus_Methanofastidiosum, etc. The metabolic behaviors of methanol are bioelectrochemistry-dependent, and controlling external voltage is thus an effective strategy for ensuring robust electron transfer, low membrane fouling, and long-term process stability.

Sustainability for wastewater treatment: bioelectricity generation and emission reduction

This review covers the technological measures of a self-sustainable anaerobic up-flow sludge blanket (UASB) system compared with an aerobic activated sludge process (ASP) for wastewater treatment plants (WWTPs). The ASP requires a huge amount of electricity and chemicals and also results in the emission of carbon. The UASB system, instead, is based on greenhouse gas (GHG) emission reduction and is associated with biogas production for cleaner electricity. WWTPs including the ASP system are not sustainable due to the massive financial power required for clean wastewater. When the ASP system was used, the amount of production was estimated to be 10658.98 tonnes CO₂eq-d^- of carbon dioxide. Whereas it was 239.19 tonnes CO₂eq-d^-1 with the UASB. The UASB system is advantageous over the ASP system as it has a high production of biogas, needs low maintenance, yields a low amount of sludge, and is also a source of electricity that can be used as a power source for the WWTPs. Also, the UASB system produces less biomass, and this helps in reducing costs and maintaining work. Moreover, the aeration tank of the ASP needs 60% of energy distribution; on the other hand, the UASB consumes less energy, approximately 3-11%.

Performance of an Innovative Low-Cost Recycled Filling (LCRF) in Anaerobic Treatment of Dairy Effluent-A Pilot-Scale Study

The rapid growth in dairy production leads to increasing outputs of high-load effluent, necessitating new methods of treating such waste. Anaerobic processes have been increasingly popular but are hamstrung by limited nutrient removal efficiency. The aim of the present study was to investigate whether low-cost recycled filling (LCRF) improves the anaerobic treatment of dairy effluent. The addition of LCRF was found to increase both COD removal (86.1 ± 2.6%-92.8 ± 1.6%) and P_tot. removal (22.1 ± 3.5% to 36.9 ± 4.6%) from the wastewater. The LCRF ensured near-neutral pH and stabilized the structure of the anaerobic microbe community (including Archaea) across all pollutant loads tested. This translated to efficient biogas production and high methane content in the LCRF reactors, peaking at 0.35 ± 0.01 m³/kg COD_removed and 68.2 ± 0.6% (respectively) in the best-performing variant.