Anaerobic Membrane Bioreactor Research Articles

Polysulfone-reinforced quorum quenching media with silica cage encapsulation: Advancing biofouling control in anaerobic membrane bioreactors

Microbial quorum quenching (QQ) using live QQ cells entrapped in a hydrophilic polymer network (e.g., hydrogel) reduces membrane biofouling but encounters challenges regarding mechanical robustness and long-term stability. This study addresses this limitation by developing a novel composite biomedia that encapsulates QQ cells (Rhodococcus sp. BH4) within porous silica cages, which act as a protective barrier against solvent exposure, and further reinforces the structure with polysulfone, a thermally and chemically stable polymer. Surface observations confirmed the successful encapsulation of the cells within the silica matrices. Further analyses revealed the distinct nature of the composite media composed of QQ bacteria, silica, and polymer networks with an amorphous structure essential for flexibility and cell viability. The mechanical properties of the polysulfone-reinforced biomedia were significantly improved, with tensile strength nearly four times higher than that of the conventional hydrogel-based biomedia, making it far more durable for long-term applications. When exposed directly to the solvent dimethylacetamide, unprotected BH4 cells experienced severe death and inactivation; however, encapsulation in the porous silica cages maintained 70% cell viability and 77% QQ activity, demonstrating the protective efficacy of the silica matrix. In anaerobic membrane bioreactor applications, the reinforced QQ media showed remarkable biofouling mitigation, extending operational times by approximately threefold and twofold compared to reactors with no media and vacant media, respectively. Using composite QQ media led to significant reductions in the concentrations of biopolymers and quorum-sensing signal molecules, contributing to prolonged membrane service times without negatively impacting overall treatment performance. These findings represent a significant advancement in developing QQ media for antifouling, sustaining the functionality of live QQ cells within durable polymer matrices.

Integrated coagulation-flocculation with nanofiltration and reverse osmosis membrane for treating sugar cane industry effluent

Sugarcane industries, like other agro-food industries, generate significant volumes of wastewater containing high concentrations of organic and inorganic pollutants. Among the proposed treatment solutions, the anaerobic membrane bioreactor (AnMBR) has proven highly effective in degrading organic pollutants but has limitations in removing color and inorganic pollutants. To address this gap, integrating other technologies with AnMBR is necessary. In this study, we propose coupling AnMBR with either Coagulation-flocculation followed by nanofiltration or reverse osmosis for treating wastewater from sugar industries after initial AnMBR treatment. The wastewater treated by an anaerobic AnMBR pilot plant, fed with wastewater from a sugar cane production unit, was used for the tests. Various formulations of Moringa oleifera were tested, including its defatting and dehulling products with hexane and ethanol. For nanofiltration and reverse osmosis, pressures of 4 and 8 bars respectively were applied. For the coagulation-flocculation phase, granular alum and powdered moringa oleifera seeds were compared as coagulants. Thus, the coupling of the coagulation-flocculation system with nanofiltration and reverse osmosis membranes effectively reduced both organic and inorganic matter. The use of aluminum sulphate proved more effective at high pollution concentrations, while Moringa oleifera extracted with hexane achieved removal rates exceeding 70 % for heavy metals (Cd, Cr, Cu, Zn). Purification efficiencies of over 90 % were obtained after filtration with the reverse osmosis membrane, while the nanofiltration membrane showed retention rates of 90 % for color, but less than 50 % for monovalent ions. The treated effluent at the outlet of the nanofiltration and reverse osmosis systems complies with Burkina Faso's discharge standards, with superior quality allowing for direct reuse in the industry.

Anaerobic membrane bioreactor (AnMBR) with external ultrafiltration membrane for the treatment of sugar beet vinasse.

Vinasse, a by-product of ethanol production, is generated at significant rates. While rich in nutrients such as calcium, magnesium, and potassium, its high solids, organic matter, acidity, and sulfate content pose challenges when disposed directly on soil, necessitating treatment. Anaerobic digestion is a viable solution, reducing organic pollution while recovering energy in the form of biogas, aligning with the biorefinery concept. Traditionally, sludge bed reactors and anaerobic contact reactors are utilized for vinasse processing, with sludge granulation being vital for treatment success. However, challenges such as sludge wash-out due to recalcitrant compounds, high solids concentration in the influent, low pH, salinity, and temperature hinder granule formation. Anaerobic membrane bioreactors (AnMBR) offer an alternative, simplifying treatment by integrating intensified pre- and post-treatment units. Due to complete sludge retention, AnMBRs achieve high COD removal efficiencies, yielding a suspended solids-free and largely disinfected effluent. Therefore, AnMBRs show promise for vinasse treatment, eliminating the need for sludge granulation and producing nutrient-rich effluent with minimal residual organics and suspended solids. In this study, an AnMBR equipped with an inside-out external crossflow ultrafiltration membrane was proposed for the treatment of vinasse. The AnMBR reached a COD removal efficiency of 95% ± 2.6% and produced 0.3 CH4 L.g COD removed -1 working at organic loading rates of 8g COD. L-1 d-1 and membrane fluxes of 10 LMH. At organic loading rates of 10g COD. L-1 d-1 and fluxes of 12 and 14 LMH, the COD removal efficiency decreased to 77% ± 11% and 73% ± 7.9%, respectively. The AnMBR technology represents an innovation for wastewater treatment, however, more research using the cross-flow configuration and different types of effluents is needed. Literature studies that address the treatment of sugar beet or sugarcane vinasse using AnMBR are still scarce. This study explored the potentials of AnMBR technology for vinasse treatment and contributes to the dissemination of this technology, opening new possibilities for vinasse processing.

Bioplastic’s Valorisation by Anaerobic Co-Digestion with WWTP Mixed Sludge

Bioplastics are designed to degrade at the end of their lifecycle, but effective management of their end-of-life phase and integration into existing organic waste management systems remain significant challenges. Some bioplastics decompose under anaerobic conditions, with the anaerobic digestion (AD) process being a potential solution for their disposal. AD is a promising technology for valorising organic wastes, enabling biomethane production, reducing carbon footprints, and promoting product circularity. This study focuses on evaluating the continuous co-digestion of bioplastics with mixed sludge from an urban wastewater treatment plant (WWTP). Polyhydroxybutyrate (PHB) was the selected bioplastic, as various studies have reported its high and rapid degradation under anaerobic mesophilic conditions. PHB’s biodegradability under typical WWTP anaerobic digestion conditions (35 °C, 20-day retention time) was assessed in batch tests and the results indicate that PHB degradation ranged from 68 to 75%, depending on particle size. To further explore the potential of AD for PHB valorisation, the feasibility of anaerobic co-digestion of PHB with WWTP sludge was tested on a continuous laboratory scale using two digesters: a conventional digester (CSTR) and an anaerobic membrane bioreactor (AnMBR). The results indicated complete degradation of PHB, which led to higher biomethanisation percentages in both digesters, rising from 58% to 70% in the AnMBR and from 44% to 72% in the CSTR. The notable increase observed in the CSTR was attributed to changes in microbial populations that improved sludge biodegradability.

CO2 removal from biogas improved stable treatment of low-alkalinity municipal wastewater using anaerobic membrane bioreactor

This study addressed a less-reported issue: the insufficient alkalinity encountered when anaerobic membrane bioreactors (AnMBRs) are used to treat municipal wastewater (MWW). In the present study, a 20-L AnMBR was initiated at an MWW treatment plant. During the initial startup, a continuous decrease in pH was observed. Through the analyses of the balance between HCO3–/CO2 in the biogas and alkalinity in the reactor, the cause of pH instability was determined to be that the alkalinity could not balance the acidity induced by the continuous dissolution of CO2 from biogas in the liquid phase. Therefore, this study employed the in-situ removal of CO2 from biogas using soda lime to reduce the CO2 partial pressure, thereby achieving stable control of the pH in the reactor. This study provides valuable experience and technical support for anaerobic processes for treating low-alkalinity MWW in the future applications.

Electrochemically Coupled Anaerobic Membrane Bioreactor Facilitates Remediation of Microplastic-Containing Wastewater

Ubiquitous microplastics (MPs) severely affect the efficiency of anaerobic membrane bioreactors (AMBR) for wastewater treatment and energy recovery by inhibiting the metabolic activity of anaerobic microorganisms. The electrochemical system can not only accelerate waste metabolism but also improve microbial resistance by promoting interspecies electron transfer within the system, which has broad application potential in the remediation of MPs wastewater. This paper attempts to evaluate the effect of electrical stimulation on the efficiency of biological wastewater treatment processes containing MPs employing an electrochemical system coupled to an anaerobic membrane bioreactor (ECAMBR). The results showed that although MP exposure inhibited methanogenic performance, electrical stimulation effectively alleviated this inhibitory effect. Further analysis showed that microplastics increased cell damage and affected enzyme activity, but electrical stimulation could affect the stress response of microorganisms, leading to changes in their cell viability and enzyme activities. The 16S-rRNA sequencing indicated that the highest abundance of hydrolytic–acidogenic bacteria Firmicutes and Bacteroidota was found at the phylum level, whereas at the genus level, it was Christensenellaceae_R-7_group, and methanogens were dominated by Methylomonas, Methyloversatilis, and Methylobacter. Functional prediction analysis indicated that carbohydrate metabolism, amino acid metabolism, and energy metabolism were the dominant metabolic pathways and that electrical stimulation could enhance their activities. This study demonstrated the important role of electrochemical stimulation in the remediation of wastewater containing high concentrations of MPs.

Treatment of sugarcane vinasse in AnMBR and UASB: process performance and microbial community comparison.

Vinasse is a by-product of sugarcane processing which is often used in fertigation; however, the direct use of vinasse harms the environment and reduces soil productivity due to its physicochemical properties. Anaerobic digestion (AD) offers an alternative to mitigate part of the negative effects. Anaerobic high-rate reactors, which mainly rely on sludge granulation, are mostly used in AD of vinasse wastewater. However, the composition of vinasse such as high concentration of solids and organic matter, high salinity, low pH, and high concentrations of sulfate, affect granule formation, leading to sludge washout. Anaerobic membrane bioreactors (AnMBR) present an alternative for vinasse treatment, eliminating the need for sludge granulation and producing a nutrient-rich effluent with minimal residual organics and no suspended solids. Research on sugarcane vinasse treatment using AnMBRs is limited. Most studies have employed submerged internal membrane modules, highlighting the need for further research with different reactor configurations to enhance process performance. In this study, an AnMBR equipped with an external inside-out crossflow ultrafiltration membrane was compared to an upflow anaerobic sludge blanket (UASB) reactor for the treatment of sugarcane vinasse. At a volumetric organic loading rate of up to 6g COD. L-1.d-1, the UASB reactor reached 75% ± 7% of COD removal efficiency whereas the AnMBR generated a solids-free effluent and reached 88% ± 2% of COD removal efficiency. Microorganisms such as Clostridia, Bacteroidia, Mesotaga, Syner-01, Dehalococcoidia, Bacteroidia-DMER64, and Methanolinea were found as the most abundant. The results highlight the AnMBR potential as an effective alternative for treating sugarcane vinasse while overcoming the challenges posed by unsatisfactory sludge granulation.

A deeper investigation of membrane fouling in anaerobic membrane bioreactors for wastewater treatment: Influencing factors and fouling layer characteristics

Identifying the core parameters affecting membrane fouling and analyzing fouling layer characteristics are crucial for membrane fouling mitigation of anaerobic membrane bioreactors (AnMBRs). This study investigated the influence of various operating parameters on membrane fouling and the characteristics of different fouling layers. The ratio of flux to specific gas demand per unit of membrane area (SGD) was proposed as a key parameter for membrane fouling control and was applicable under various flux, SGD, and sludge concentration conditions. The membrane resistance and specific filtration resistance of foulants at high flux and sludge concentration reached 1.56 × 1012 m−1 and 3.56 × 1015 m−1/kg, respectively. Solid foulants accumulated on the membrane surface during rapid fouling stage. Protein-like pollutants accounted for a higher proportion (85%) of soluble foulants on the membrane surface. Humic acids were enriched on the cake/gel layer and the longitudinal enrichment process from the cake layer to the gel layer was uneven. Proteocatella (>45%) at the phylum level, Desulfovibrio (>3.1%), Syntrophobacter (>2.8%), and Treponema (>0.25%) at the genus level colonized in the gel layer and were the pioneers of membrane biofouling. Their enrichment on the membrane surface was primarily based on their own characteristics and was less sensitive to the operating conditions of AnMBRs. Therefore, this study provides a deeper understanding of membrane fouling formation process, which contributes to the long-term stable operation of AnMBR and scales up its engineering application.

Mechanisms and Enhancement of Hydrogen Evolution for Membrane Anti-fouling and Methane Upgrading by Sacrificed Anode in a Novel Electro-AnMBR

Severe membrane fouling and low CH4 content in the produced biogas have restricted the applicability and energy recovery profit of the anaerobic membrane bioreactor (AnMBR). Herein, a novel AnMBR was constructed with an electrochemical hydrogen evolution reaction (electro-HER) by double anodes and a titanium membrane-cathode (eHAnMBR). The electro-HER was controlled and enhanced by sacrificed iron anode under low voltage, to mitigate membrane fouling and upgrade biogas simultaneously. The critical factors in electro-HER were investigated to influence the AnMBR system, including hydrogen, applied voltage, and Fe ions. The voltage and hydrogen enhanced the hydrogenotrophic methanogenesis process and enriched hydrophilic Methanobacterium and Methanosarcina, thereby improving biogas purity by up to 28% and increasing total CH₄ production by 46%. Furthermore, the electro-HER on the membrane-cathode decreased the transmembrane pressure by 30%. Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMs) was innovatively applied to visualize the organic foulants in membrane pores. The electro-HER not only produced H2 to optimize cake layer structure but also produced local alkalinity on the membrane surface, to remove extracellular polymeric substances in membrane pores. Additionally, Fe2+/Fe3+ released from the sacrificial iron anode, facilitated phosphate precipitation and removal from 15.7% to 37.9%. This study presents a novel and sustainable wastewater treatment solution by integrating the electro-HER process with AnMBR, enabling both energy recovery and membrane antifouling.

Optimization based process modeling of an anaerobic membrane bioreactor system: Application to swine wastewater

To maintain current levels of consumption in the economy with the dwindling supply of non-renewable material and energy, alternative resource streams more traditionally viewed as waste streams must be considered. Fermentation of high-strength wastewaters is one such pathway that allows for the recovery of energy, nitrogen, phosphorus, and carbon compounds. Anaerobic membrane bioreactors (AnMBRs) are an emerging technology that allow for the digestion of wastewater in a much smaller footprint than traditional anaerobic digesters. Adoption of this technology into industry has been limited by membrane capital and cleaning costs, but these costs may be offset through the recovery of valuable products. To evaluate the viability of AnMBR technology in the context of swine wastewater treatment, an optimization-based process model built upon Anaerobic Digestion Model No. 1 (ADM1) has been developed. Modeling results show that a swine wastewater stream provides potential for net positive energy generation from the AnMBR system in most cases. Sensitivity analyses around important variables were conducted to determine focus areas for future research into AnMBR technology and evaluate the robustness of the model to microbial variables that may change with different microbial communities.

Granular anaerobic membrane bioreactor coupled hybrid forward osmosis − membrane distillation module for organic matter, nutrient and bisphenol A removal: Integrated assessment of performance, cost, toxicity, and risks

Bisphenol A (BPA), a compound widely produced and used worldwide, has been increasingly investigated due to its potential risk to human health and the environment. Studies and regulations have focused on its presence in materials in contact with food and children’s products; however, BPA has been detected in several aquatic matrices, reaching water bodies, mainly due to its incomplete removal in wastewater treatment plants, which may lead to even greater hazards. Therefore, this study investigated for the first time a granular anaerobic membrane bioreactor associated with a hybrid module of forward osmosis – membrane distillation (G-AnOMBR/MD) focusing on removing BPA in domestic sewage. In addition, the removal of organic matter and nutrients was evaluated concomitantly at the ecotoxicological tests, risk assessment, and cost evaluation. The results showed that the average COD, P-PO43−, and N-NH4+ removal was 95.6 %, 99.6 %, and 91 %, respectively. The removal of BPA was 94.65 % after 30 days of operation due to the granular sludge biodegradation and the higher selectivity of the FO-MD module. In addition, the system eliminated the high environmental and human health risks related to BPA, and the final effluent was non-toxic to the bacteria Aliivibrio fischeri. Finally, the estimated cost for G-AnOMBR/MD was US$ 3.91 m−3. Thus, the technology is promising for generating a high-quality and safe effluent regarding the presence of BPA and being financially competitive with other advanced systems.

Unveiling the evolution of anaerobic membrane bioreactors: applications, fouling issues, and future perspective in wastewater treatment

Unveiling the evolution of anaerobic membrane bioreactors: applications, fouling issues, and future perspective in wastewater treatment

Novel insights into fouling mechanisms in anaerobic acidification membrane bioreactor: The leading role of pH value

Anaerobic acidification membrane bioreactors (AAMBRs) have recently emerged as effective systems for recovering volatile fatty acids (VFAs) from municipal wastewater. However, membrane fouling remains a critical challenge, with its underlying mechanisms not yet fully understood. Given its importance in inhibiting methanogenic bacteria and stabilizing VFAs production, this study explores the direct and indirect effects of pH on membrane fouling mechanisms in AAMBRs. The results demonstrated that compared to pH 7, the fouling potential of anaerobic sludge was significantly higher at pH levels of 5 and 10 owing to a decrease of sludge floc size and an increase of soluble microbial products (SMP) especially proteins. Analytical techniques such as confocal laser scanning microscopy (CLSM), fourier transform infrared spectroscopy (FTIR), and fluorescence excitation-emission matrix (F-EEM) analyses revealed a substantial increase in organic foulants particularly proteins on the membrane surface at pH levels of 5 and 10. Circular dichroism (CD) spectroscopy further indicated a significant change in protein secondary structure, specifically an increase in α-helix content under extreme pH conditions. Furthermore, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory indicated that elevated protein concentrations enhance the adhesion of sludge and SMP to membrane surfaces. Insights from the Flory-Huggins theory demonstrated that variations in protein structure significantly contribute to increased filtration resistance within the gel layer. Both experimental data and theoretical models underscore the dual role of pH in optimizing VFAs production and managing membrane fouling, offering insights for enhancing AAMBR performance and mitigating fouling issues.

Recovering nutrients and unblocking the cake layer of an electrochemical anaerobic membrane bioreactor

The sustainable development strategy shifts water treatment from pollution removal to resource recovery. Here, an electrochemical resource-recovery anaerobic membrane bioreactor (eRAnMBR) that employed a magnesium plate and conductive membrane as dual anodes is presented and shows excellent performance in carbon, nitrogen, and phosphorus recovery, as well as 95% membrane anti-fouling. The Mg2+ released alters the physicochemical properties of sludge, unblocking the cake layer, and recovers ammonium and phosphate, yielding 60.64% purity and 0.08 g d−1 struvite deposited onto cathode to be separated from sludge. The enhanced direct interspecies electron transfer, along with hydrogen evolution and alkalinity increase due to the electrochemical reactions, significantly increase methane yield and purity (93.97%) of the eRAnMBR. This increased internal energy can cover the additional electricity and electrode consumption. This integrated eRAnMBR reactor boasts the benefits of short process, low maintenance, and low carbon footprint, introducing a concept for the next generation of wastewater treatment.

Enhanced nitrogen removal from low strength anaerobic membrane bioreactor (AnMBR) permeate using complete nitrification and partial denitrification-anammox processes

Enhanced nitrogen removal from low strength anaerobic membrane bioreactor (AnMBR) permeate using complete nitrification and partial denitrification-anammox processes

Non-electroactive bacteria behave variously in AnMBR biofilm control using electric field

Electroactive bacteria are often regarded as key players responding to electric fields that are used to control biofilm development during AnMBR (anaerobic membrane bioreactor) operation. Consequently, little attention has been given to non-electroactive bacteria in the same systems because of their incapability to acquire and transfer electrons directly. However, in this study, we identified some functionally important non-electroactive bacteria from biofilm established under low-voltage (0, 0.3, 0.5 and 1 V) electric fields in AnMBRs, designated as E-AnMBRs in this study. During the whole experiment, non-electroactive bacteria, mainly belonging to Proteobacteria, Bacteroidetes, and Chloroflexi, were found in all biofilm samples taken from each E-AnMBR. Under 0.3 V and 1 V conditions, non-electroactive bacteria did not seem to contribute to the development of biofilm significantly. Whereas under 0.5 V conditions, the growth of non-electroactive bacteria contributed up to 0.61 kPa/day biofilm formation. Therefore, 0.5 V was identified as a critical voltage, leading to the most severe biofilm formation. The microbial community structure in the reactor with a 0.5 V electric field was distinctly unique, caused by the increase of non-electroactive bacterial activity and the upregulation of their metabolic pathways. Notably, functional genes involved in carbon metabolism and oxidative phosphorylation pathway were upregulated. Furthermore, the 0.5 V electric field enhanced the protein/polysaccharide ratio and increased zeta potential to 31.6 mV (p < 0.01) of the biofilm samples. This was because upregulating quorum sensing genes accelerated the coordinated gene regulations and functional activities among non-electroactive bacteria.

Ion exchange columns. A promising technology for nitrogen and phosphorus recovery in the main line of a wastewater treatment plant

Anaerobic membrane bioreactor (AnMBR) technology has great advantages for treating urban wastewaters, but, when irrigation cannot be applied and the effluent is discharged in a sensitive zone, a post-treatment of this effluent is needed for nitrogen and phosphorus removal. Under this scenario, ion exchange processes represent one of the most promising technologies for treating this effluent. Ion exchange technology allows to meet discharge limits and to recover these nutrients in a highly concentrated stream. In this work, the technical feasibility of using a commercial resin for phosphorus recovery and a natural zeolite (clinoptilolite) for nitrogen recovery was evaluated. Purolite FerrIX A33E resin removed phosphate from the AnMBR permeate within 500 Bed Volumes (BVs) with a maximum adsorption capacity (qmax) of 2,1 mg P-PO4/g resin. Regeneration of the resin (2% NaOH 2% NaCl) recovered over 95% of the phosphorous retained, achieving a concentration of 316,7 mg P-PO4/L in the regeneration solution. In the absence of a long-term study, the resin showed a stable adsorption capacity during 16 cycles of saturation-regeneration. Clinoptilolite removed nitrogen within 139 BVs obtaining a qmax of 3,68 mg N-NH4/g zeolite. 97 % of the retained N-NH4 was recovered in the regeneration stage (0,8% NaOH) with an average concentration of 577 mg N-NH4/L. Continuous exposure of the zeolite to alkaline solutions led to reduction of 50% of the adsorption capacity after 17 cycles.

Longitudinal wastewater-based surveillance of SARS-CoV-2 during 2023 in Ethiopia.

Although wastewater-based epidemiology (WBE) successfully functioned as a tool for monitoring the coronavirus disease 2019 (COVID-19) pandemic globally, relatively little is known about its utility in low-income countries. This study aimed to quantify severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in wastewater, estimate the number of infected individuals in the catchment areas, and correlate the results with the clinically reported COVID-19 cases in Addis Ababa, Ethiopia. A total of 323 influent and 33 effluent wastewater samples were collected from three Wastewater Treatment Plants (WWTPs) using a 24-h composite Moore swab sampling method from February to November 2023. The virus was captured using Ceres Nanotrap® Enhancement Reagent 2 and Nanotrap® Microbiome A Particles, and then nucleic acids were extracted using the Qiagen QIAamp Viral RNA Mini Kit. The ThermoFisher TaqPath™ COVID-19 kit was applied to perform real-time reverse transcriptase polymerase chain reaction (qRT-PCR) to quantify the SARS-CoV-2 RNA. Wastewater viral concentrations were normalized using flow rate and number of people served. In the sampling period, spearman correlation was used to compare the SARS-CoV-2 target gene concentration to the reported COVID-19 cases. The numbers of infected individuals under each treatment plant were calculated considering the target genes' concentration, the flow rate of treatment plants, a gram of feces per person-day, and RNA copies per gram of feces. SARS-CoV-2 was detected in 94% of untreated wastewater samples. All effluent wastewater samples (n = 22) from the upflow anaerobic sludge blanket (UASB) reactor and membrane bioreactor (MBR) technology were SARS-COV-2 RNA negative. In contrast, two out of 11 effluents from Waste Stabilization Pond were found positive. Positive correlations were observed between the weekly average SARS-CoV-2 concentration and the cumulative weekly reported COVID-19 cases in Addis Ababa. The estimated number of infected people in the Kality Treatment catchment area was 330 times the number of COVID-19 cases reported during the study period in Addis Ababa. This study revealed that SARS-CoV-2 was circulating in the community and confirmed previous reports of more asymptomatic COVID-19 cases in Ethiopia. Additionally, this study provides further evidence of the importance of wastewater-based surveillance in general to monitor infectious diseases in low-income settings. Wastewater-based surveillance of SARS-CoV-2 can be a useful method for tracking the increment of COVID-19 cases before it spreads widely throughout the community.

Characteristics and fouling behaviors of soluble microbial products and sub-visible particles in an anaerobic membrane bioreactor treating sewage at room temperature

A lab-scale anaerobic membrane bioreactor (AnMBR) was employed to investigate the characteristics and fouling behaviors of soluble microbial products (SMP) and sub-visible particles (SVP) in sewage treatment. The study revealed a noteworthy trend, where SMP and SVP concentrations initially surged, subsequently declined, and ultimately stabilized at comparable levels. Compositions and fluorescent property analyses indicated that protein-like substances with tryptophan are the primary fluorescent composition in both SMP and SVP. Notably, SVP exhibited a superior protein concentration and a higher protein-to-polysaccharide ratio, thereby resulting in a higher filtration resistance than SMP. Moreover, microbial species involved in biofouling (Rhodocycales and Desulfovibrionales) also have a higher abundance in SVP, meaning SVP has a higher biofouling potential than SMP. Achievements in this study expanded the knowledge of the characteristics of SMP and SVP and revealed the significant role of SVP in membrane fouling of AnMBR.

Evaluating a hybrid process of anaerobic digestion, aerobic degradation, and electrochemical separation for swine wastewater treatment with methane and nutrient recovery

A hybrid process of anaerobic digestion (AD), aerobic degradation, and electrochemical separation was evaluated for treating real swine wastewater that is rich in organic and nutrient to achieve methane and nutrient recovery and industry standard discharge quality. Fe anode electrocoagulation and Mg anode struvite electrochemical precipitation (SEP) were evaluated as AD pretreatments. Both removed partial chemical oxygen demand (COD) from raw swine wastewater, but only SEP slightly enhanced the methane yield of pretreated swine wastewater. The SEP efficiency of the AD effluent was significantly better than raw swine wastewater. A further coupled micro/ultra-filtration produced high-purity (96%) struvite. SEP and struvite chemical precipitation (SCP) were evaluated for AD effluent treatment. This showed that compared with SCP following first-order reaction kinetics (reaction rate constant of 0.791 and 0.854 h−1 for NH4+-N and PO43--P), SEP not only achieved better removal of COD, NH4+-N and PO43--P, but was also shown to follow zero-order reaction kinetics (reaction rate constant of 5.72 and 5.78 mmol L−1 h−1 for NH4+-N and PO43--P). The SEP and SCP treated AD effluent was evaluated by conventional activated sludge (CAS), showing faster COD removal (first-order reaction rate constant of 0. 213 and 0.163 h−1) and lower residual COD (150 and 248 mg L−1) from SEP than SCP treated AD effluent, making the final effluent well below Chinese livestock wastewater discharge standards. Therefore, an emerging hybrid anaerobic membrane bioreactor (AnMBR)-SEP-CAS is proposed for swine wastewater treatment and proved to be more economically viable than the conventional hybrid AD-SCP-CAS process via cost-benefit analysis.