Anaerobic Osmotic Membrane Bioreactor Research Articles

A comparative study on UASB MF-OMBR and AnMF-OMBR treating slaughterhouse wastewater: Process performance, struvite precipitation, and economic evaluation

Up-flow anaerobic sludge blanket microfiltration osmotic membrane bioreactor (UASB MF-OMBR) is a cutting-edge technology derived from the anaerobic osmotic membrane bioreactor (AnOMBR). This study investigated long-term performance of an UASB MF-OMBR and an anaerobic microfiltration osmotic membrane bioreactor (AnMF-OMBR) comparatively focusing on process performance, membrane fouling, microbial community shift, struvite precipitation, and economic evaluation for the treatment of synthetic and real slaughterhouse wastewater (SSW and RSW). The UASB MF-OMBR achieved higher process performance regarding chemical oxygen demand (COD) removal (70 ± 1 %), methane yield (0.24 ± 0.03 L CH4 g−1 CODremoved) and NH4+-N rejection (85 ± 3 %). On the other hand, high COD and PO43−-P rejections were observed in both systems (>92 % and ∼98 %, respectively). The impact of the salinity build-up in the UASB MF-OMBR was the lower due to the bioreactor configuration. In addition, compared to the AnMF-OMBR, the better water fluxes were obtained in the UASB MF-OMBR, which can be attributed to the less membrane fouling. The results of precipitation modelling and Mg2+ measurement in the sludge of both bioreactors demonstrated that the struvite precipitation occurred during the forward osmosis (FO) operation was more often and in higher amounts in the AnMF-OMBR. The economic evaluation indicated that the specific produced permeate cost (SPC) with revenue was slightly lower for the UASB MF-OMBR than that of the AnMF-OMBR.

A hybrid anaerobic osmotic membrane bioreactor - membrane distillation for water reclamation: aquatic toxicity, membrane fouling characterization, and economic assessment

The incomplete removal of pharmaceutically active compounds (PhACs) by conventional wastewater treatment has been challenging due to their ecological implications. Therefore, advanced technologies are necessary to remove PhACs efficiently. In the present study, an anaerobic osmotic membrane bioreactor - membrane distillation (AnOMBR-MD), aiming to remove seven PhACs, was evaluated by an integrated approach, considering the environmental toxicity, fouling characterization, and economic assessment. PhACs removal was evaluated using liquid chromatography coupled with mass spectrometry. Besides, organic matter and nutrient removal were evaluated. The FO and MD membrane fouling was characterized with scanning electron microscopy and energy dispersive spectroscopy. Toxic effects were analyzed for Aliivibrio fischeri, Daphnia similis, and Raphidocelis subcapitata. Furthermore, a preliminary economic assessment was carried out using capital and operating expenditures. The results showed a DOC, N-NH4+, and P-PO43- removal of 92%, 97%, and 99.9%, respectively, while removal of PhACs was >96%. However, the distillate was classified as very toxic forR. subcapitata, and a strong correlation was found between toxicity and the Mg2+ originating from the draw solution (DS). This result showed the importance of including toxicity tests in the selection of DS. The economic evaluation indicated that the higher cost is related to the membrane replacement due to the decrease in the permeate flux, pointing out the need for future studies that address cleaning strategies to solve the organic and inorganic fouling on the membrane's surface. In this sense, this study promoted an improvement in understanding the AnOMBR-MD technical-economic viability aiming at full-scale application.

High−saline and long−term treatability of industrial wastewater by AnOMBR using organic and inorganic draw solutions

Less costly to AnMBR, anaerobic osmotic membrane bioreactor (AnOMBR) proceeds water and energy−efficient progresses within green and cleaner technologies. Long−term effectively operation of AnOMBR in high salinities due to salt accumulation is of the greatest priority, accompanied with a cost−performance efficient and non−inhibitory draw solution (DS) usage. Operational stability of AnOMBR in industrial wastewater treatment was studied at 30 mS/cm using the most favorable organic and inorganic DS within 29 DSs in our prior work, namely HCOONa and CaCl2. Osmotic and microbial yields during unintervented operations were lost due to severe salt stress and membrane biofouling. With a virgin membrane replacement, removal efficiencies, water and salt flux selectivity were partially restored, but the AnOMBRs turned towards collapse due to microbial activity lost. Therefore, sludge inoculation was applied and improved all AnOMBR performances to levels so close to before losses with 78 ± 3 % COD and 98.3 ± 0.6 % PO43-–P, 0.44 ± 0.2 L CH4/d excluding NH4+–N of 44 ± 10 %. It was designated that reverse salt passage for both the DS was responsible for approximately two-thirds of in-reactor salt build-up during stable AnOMBR operations. Statistical analysis results of the AnOMBR system for HCOONa and CaCl2 showed that statistical significances of performances in treatments with both DSs were from moderate to strong evidence levels. Microbial diversity increased by salt accumulation, and archaeal community differentiated. HCOONa promoted hydrogenotrophic halotolerant methanogenic archaeas, but not by CaCl2. Biofilm formed predominantly by biomass, Na+/Ca2+−bound biopolimers and inorganic precipitates provided bioactively better C, N, and P exhaustions in more porous and thicker secondary membrane layer by HCOONa. Beyond a virgin membrane replacement and sludge inoculation, an AnOMBR can be efficiently operated by sludge acclimation to high salinities, finest membrane clean-up, and even fabrication of FO membrane with the integrated nano-structured novel membranes such as including silver, nanofibers, graphene oxides etc.

Improving biological removal of pharmaceutical active compounds and estrogenic activity in a mesophilic anaerobic osmotic membrane bioreactor treating municipal sewage.

The contamination of water sources by pharmaceutically active compounds (PhACs) and their effect on aquatic communities and human health have become an environmental concern worldwide. Membrane bioreactors (MBRs) are an alternative to improve biological removal of recalcitrant organic compounds from municipal sewage. Their efficiency can be increased by using high retention membranes such as forward osmosis (FO) and membrane distillation (MD). Thus, this research aimed to evaluate the performance of an anaerobic osmotic MBR coupled with MD (OMBR-MD) in the treatment of municipal sewage containing PhACs and estrogenic activity. A submerged hybrid FO-MD module was integrated into the bioreactor. PhACs removal was higher than 96% due to biological degradation, biosorption and membrane retention. Biological removal of the PhACs was affected by the salinity build-up in the bioreactor, with reduction in biodegradation after 32d. However, salinity increment had little or no effect on biosorption removal. The anaerobic OMBR-MD removed >99.9% of estrogenic activity, resulting in a distillate with 0.14ngL-1 E2-eq, after 22d, and 0.04ngL-1 E2-eq, after 32d. OMBR-MD treatment promoted reduction in environmental and human health risks from high to low, except for ketoprofen, which led to medium acute environmental and human health risks. Carcinogenic risks were reduced from unacceptable to negligible, regarding estrogenic activity. Thus, the hybrid anaerobic OMBR-MD demonstrated strong performance in reducing risks, even when human health is considered.

Water reclamation and microbial community investigation: Treatment of tetramethylammonium hydroxide wastewater through an anaerobic osmotic membrane bioreactor hybrid system

Tetramethylammonium hydroxide (TMAH) is a toxic photoresist developer used in the photolithography process in thin-film transistor liquid crystal display (TFT-LCD) production, and it can be removed through anaerobic treatment. TMAH cannot be released into the environment because of its higher toxicity. A tight membrane, such as a forward osmosis (FO) membrane, together with an anaerobic biological process can ensure that no TMAH is released into the environment. Thus, for the first time, an anaerobic osmotic membrane bioreactor (AnOMBR) hybrid system was developed in this study to treat a low-strength TMAH wastewater and to simultaneously investigate its microbial community. Microfiltration extraction was used to mitigate the salinity accumulation, and a periodically physical water cleaning was utilized to mitigate the FO membrane fouling. The diluted draw solute (MgSO4) was reconcentrated and reused by a membrane distillation (MD) process in the AnOMBR to achieve 99.99% TMAH removal in this AnOMBR-MD hybrid system, thereby ensuring that no TMAH is released into the natural environment. Moreover, the membrane fouling in the feed and draw sides were analyzed through the fluorescence excitation-emission matrix (FEEM) spectrophotometry to confirm that the humic acid-like materials were the primary membrane fouling components in this AnOMBR. Additionally, 16S rRNA metagenomics analysis indicated that Methanosaeta was the predominant contributor to methanogenesis and proliferated during the long-term operation. The methane yield was increased from 0.2 to 0.26 L CH4/g COD when the methanogen species acclimatized to the saline system.

Deciphering mono/multivalent draw solute-induced microbial ecology and membrane fouling in anaerobic osmotic membrane bioreactor

Anaerobic osmotic membrane bioreactor (AnOMBR) attracted attention due to high quality effluent production with low energy demand, and draw solute has significant effect on the system performance. However, the mutual relationship between draw solute-induced salinity accumulation and microbial community had many unknown questions to be solved. This study purpose was to construct two AnOMBR to compare the impact of draw solutes of NaCl and MgCl2 on the dynamic change of microbial ecology and membrane fouling. The result indicated that the draw solute of MgCl2 caused less salinity and more membrane biofouling than that of the draw solute NaCl. Multiple microbiological analysis methods were applied to discover keystone species related to the conductivity change and membrane fouling, especially for the MgCl2-AnOMBR system. It was found that draw solute NaCl could benefit the growth of Proteobacteria to become the most abundant phylum to affect the membrane fouling, while Mg2+ introduction could stimulate the growth of NS9, Hydrogenphilaceae and Pedosphaeraceae to potentially cause the biofouling. Furthermore, phylogenetic molecular ecological networks (pMENs) deeply analyzed the microbial structure difference under Na+ and Mg2+ introduction, and indicated that the family Lentimicrobiaceae and Candidatus_Kaiserbacteria were the keystone species in NaCl-AnOMBR, while two genus Anaerolinea and SWB02, and two families Saprospiraceae and NS9 were discovered to have key effect in MgCl2-AnOMBR due to their strong extracellular polymeric substances (EPS) production ability for survival of other microorganisms. This study was significant to give microbial targets under the impact of various draw solutes, as the reference for the engineers to further investigate how to improve the microbial structure to enhance AnOMBR performance and inhibit the membrane biofouling.

Treatment of high‐strength synthetic textile wastewater through anaerobic osmotic membrane bioreactor and effect of sludge characteristics on flux

AbstractThe anaerobic osmotic membrane bioreactor (AnOMBR) system was evaluated for the treatment of high‐strength synthetic textile wastewater. The chemical oxygen demand (COD) concentration was above 3,000 mg/L and color above 1,300 Pt‐Co in the synthetic textile wastewater. The study was divided into six cycles of roughly nine days each. Mono ammonium phosphate with 1 M concentration was used as draw solution. Average COD and color removal efficiencies from anaerobic bioreactor were 57% ± 5% and 43.7% ± 6%, respectively; however, in OMBR permeate, these parameters were improved to 91% ± 4% and 91% ± 2%, respectively. After each cycle, membrane cleaning was performed using osmotic backwashing for 3 hours, which produced flux recovery values between 88% and 61% from cycle 2 to cycle 6, respectively. High mixing speed of the stirrer bar (600 rpm) in the bioreactor produced a greater shear force, causing a reduction in average sludge particle size from 10 to 3.5 μm. It increased the release of soluble microbial products and extra polymeric substances to cause an initial flux decline from 3.3 to 2.2 LMH from cycle 1 to cycle 6. The study proved AnOMBR as a promising technology for high‐strength synthetic textile wastewater treatment.

Effective removal of pharmaceutical compounds and estrogenic activity by a hybrid anaerobic osmotic membrane bioreactor – Membrane distillation system treating municipal sewage

Pharmaceutically active compounds (PhACs) may cause harmful effects in living beings, and advanced treatment is required to improve wastewater treatment plant efficiency. In this context, this study aimed to assess the performance of a hybrid anaerobic osmotic membrane bioreactor coupled with a membrane distillation system (AnOMBR-MD) for removing PhACs and estrogenic activity from municipal sewage. Human health and environmental risks of produced water were also assessed. The removal efficiency of dissolved organic carbon and P-PO43- reached 97.2% and 98.0%, respectively. N-NH4+ accumulated in the bioreactor since anaerobic treatment can not remove it. Salinity increase in the bioreactor caused a great change in the microbial community, with Chao 1 and Shannon indexes higher in the sludge after 50 days of operation than in the sludge used as inoculum. Estrogenic activity of municipal sewage spiked with PhACs was >3 times higher than the expected value calculated by the additive model (2 µg L−1E2-eq.), which indicates that some of the PhACs effects increased in the presence of others. Estrogenicity was not detected in distillate samples, which greatly reduced human health risks to acceptable values. Of the 7 PhACs selected in this study, only betamethasone, fluconazole, and prednisone were detected in the distillate. However, the overall removal of PhACs by the AnOMBR-MD system was higher than 96.4%. The chronic environmental risk considering the estrogenic activity was classified as high because of the detection limit in the yeast estrogen screen (YES), which supports the need for improving bioassay sensibility. The results demonstrated that the use of the YES assay combined with detection and identification of micropollutants allowed an effective assessment of the overall treatment performance.

A novel submerged anaerobic osmotic membrane bioreactor coupled to membrane distillation for water reclamation from municipal wastewater

A novel configuration of an osmotic anaerobic membrane bioreactor coupled with membrane-assisted distillation (OMBR-MD) in a single submerged module was proposed for domestic sewage treatment and potabilization. A steady permeate flux was achieved after the 22nd day of monitoring, in which the draw solution (DS) was diluted by the forward osmosis (FO) permeate at the same rate in which it was concentrated by the membrane distillation (MD). Salinity build-up inside the bioreactor contributed to fouling in the FO membrane since it increases the production of soluble microbial products and extracellular polymeric substances. In addition, organic matter accumulated in DS, due to the closed-loop system, may be the main cause for fouling in MD membranes at the latter stages. The OMBR-MD presented great removal for organic matter (91%), phosphorous (95%) and ammonium nitrogen (71%). Alkalinity accumulation within the bioreactor prevented a significant change in bulk solution pH (8.0 – 8.4), reducing the effects of volatile fatty acids production on methanogenic performance. The OMBR-MD removal efficiencies were higher than 96% for all 7 selected pharmaceutical drugs. Additionally, the MD distillate attained eight out of the nine parameters assessed for potable water standards established in Brazilian legislations and recommendations from US EPA, including Escherichia coli. Therefore, the novel OMBR-MD proved to be a feasible alternative for treating municipal wastewater, generating a high-quality distillate.

Techno-economic preferability of cost-performance effective draw solutions for forward osmosis and osmotic anaerobic bioreactor applications

Cost and performance efficient integrations of biological treatments with membrane processes are very worthy for water and resource recovery among of which osmotic anaerobic digestion suffers from exactly elucidating desirable techno-economic features of key operating factors. Cost-performance effective draw solutions (DSs) were ascertained for forward osmosis (FO) and its anaerobic bioreactor (AnBR) configurations, anaerobic osmotic membrane bioreactor (AnOMBR) and [FO/AnBR]. In case study comprising literature data pre-screening, selected DS experiments, and preferability analysis, dual modeling was executed for prioritizing DSs eligible to osmotic AnBRs by analytic hierarchy process (AHP). Through AHP screening of 29 DSs' FO data, NaNO3, NaCl, MgCl2, CaCl2, NH4H2PO4, HCOONa and CH3COONa were established between the best 10% worth researching for osmotic AnBRs. Experiments showed that isothermally varied temperatures hardly affected DS performances in submerged, but DS concentration raises led to those distinguished by reverse solute fluxes. Reverse solute flux selectivity was differed significantly by DS kinds and FO configurations because of varying interactions among predominant inorganic ion and soluble organics. Submerged FO fed by distilled water provided better performance than sidestream but not by wastewater. Anaerobic bioactivities showed longer acclimation times increased by alkalinity unlike seawater (SW) and better CH4 productivity of organics enhanced by DS concentration. Upon AHP analyses, CaCl2, MgCl2, both organics, and SW were more techno-economically favorable DS kinds. Irrespective of technological alternatives, CaCl2 and MgCl2 were found as top two except just SW was the best for AnOMBR by low-cost supply. It was finally proved that eligible DSs should be designated technology-dependently due to their distinctive performances and replenishment costs, and topmost priority to SW should be attributed in sustainable wastewater reclamations by AnOMBR in coastal countries.

Secret underneath: Fouling of membrane support layer in anaerobic osmotic membrane bioreactor (AnOMBR)

Anaerobic osmotic membrane bioreactor (AnOMBR) holds promise for simultaneous wastewater purification and biogas production, allowing for an energy and carbon-neutral treatment facility. In a typical AnOMBR, reverse osmosis (RO) is employed for re-concentrating draw solution for continuous operation and cost saving. We compared membrane fouling behaviors between AnOMBR-RO hybrid system and AnOMBR without RO unit. We concluded that the porous support layer was susceptible to both inorganic scaling and biofouling in the closed-loop AnOMBR-RO system. We also explored two cleaning approaches to mitigate inorganic scaling and biofouling. Specifically, ethylenediaminetetraacetic acid (EDTA) was introduced into draw solution for minimizing inorganic scaling, but biofouling was deteriorated as EDTA provided extra nutrients for bacterial proliferation and biofouling. On the other hand, chemical cleaning of membrane support layer was performed using NaClO solution for biofouling control, but such cleaning efficacy attenuated after several cleaning cycles, because inorganic minerals accumulated and grew within membrane porous layer which could not be flushed by NaClO cleaning. Our finding highlighted the complexity and courter intuitive perspective to membrane fouling and cleaning in AnOMBR-RO hybrid system for inorganic scaling and biofouling management.

Water and nutrient recovery by a novel moving sponge – Anaerobic osmotic membrane bioreactor – Membrane distillation (AnOMBR-MD) closed-loop system

For the first time, a novel sponge-based moving bed-anaerobic osmosis membrane bioreactor/membrane distillation (AnOMBR/MD) system using mixed Na3PO4/EDTA–2Na as the draw solution was employed to treat wastewater for enhanced water flux and reduced membrane fouling. Results indicated that the moving sponge-AnOMBR/MD system obtained a stable water flux of 4.01 L/m2 h and less membrane fouling for a period lasting 45 days. Continuous moving sponge around the FO module is the main mechanism for minimizing membrane fouling during the 45-day AnOMBR operation. The proposed system’s nutrient removal was almost 100%, thus showing the superiority of simultaneous FO and MD membranes. Nutrient recovery from the MF permeate was best when solution pH was controlled to 9.5, whereby 17.4% (wt/wt) of phosphorus was contained in precipitated components. Moreover, diluted draw solute following AnOMBR was effectively regenerated using the MD process with water flux above 2.48 L/m2 h and salt rejection > 99.99%.

Mesophilic microfiltration–anaerobic osmotic membrane bioreactor–membrane distillation hybrid system for phosphorus recovery

AbstractBACKGROUNDFor the first time, a closed‐loop anaerobic osmotic membrane bioreactor–membrane distillation (AnOMBR‐MD) hybrid system integrated with periodic microfiltration (MF) extraction was investigated for simultaneous nutrient and energy recovery while maintaining high water quality for reuse. In addition, phosphorus (P) was recovered as a valuable material for agricultural purposes.RESULTSThe AnOMBR‐MD system exhibited excellent nutrient (>99.9%) and organic removal (almost 100%) due to double‐layer filtration (FO and MD membrane). Moreover, higher methane production (0.24 L CH4/g COD) was achieved from the MF‐AnOMBR process to supply a heat source for MD during the draw solution recovery process to reduce energy consumption. The MF permeate can significantly reduce the scaling potential caused by PO43− ions in bulk solution and mitigate salt accumulation in the anaerobic reactor. The P from the MF permeate was effectively recovered with an efficacy of 60 mg L−1 when the solution pH was adjusted to 12.CONCLUSIONThe overall performance of the MF‐AnOMBR‐MD hybrid system using 1.5 mol L−1 MgSO4 as the draw solution demonstrates its potential application in wastewater treatment with high nutrient recovery in the closed‐loop system. Moreover, this system combined with MD in AnOMBR for draw solution recovery could achieve low energy consumption when its biogas production is utilized as heat source from the anaerobic system. © 2018 Society of Chemical Industry

Effect of driving force on the performance of anaerobic osmotic membrane bioreactors: New insight into enhancing water flux of FO membrane via controlling driving force in a two-stage pattern

Anaerobic osmotic membrane bioreactor (AnOMBR) has shown great promise for wastewater treatment and energy recovery. One of the major obstacles limiting the performance of the AnOMBR is the low water flux of forward osmosis (FO) membrane. Here, impacts of draw solution (DS) concentration on the performance of the AnOMBR were investigated for enhancing the water flux of FO membrane via controlling the driving force. The results indicated that the flux variations of FO membrane in the AnOMBR included two stages of a rapid and a mild flux declines at all DS concentration conditions. In addition, the FO membrane fouling correlated well with the flux variations for all DS concentration levels, i.e., a severe fouling in Stage 1 and a slight fouling in Stage 2. When the driving force or DS concentration exceeded a critical value, a worse FO membrane performance especially a severer flux decline in Stage 1 was observed. It could be attributed to an aggravated membrane fouling in Stage 1 owing to an increased initial flux with the rise of the driving force, implying that a critical initial flux exists in the AnOMBR except for a critical driving force. Inspired by the critical initial flux and the significant role of the membrane fouling in Stage 1, this study provides a novel method to enhance flux performance of FO membrane via controlling the driving force in a two-stage pattern. It utilizes a low driving force in Sage 1 to form a thin and loose fouling layer on the FO membrane surface and then a high driving force in Sage 2 to alleviate the flux drop. Compared with the stable driving force, the two-stage pattern obtained a better flux performance owing to a mitigation of membrane fouling with thinner layer thickness and less deposited foulants.

Removal of cytostatic drugs from wastewater by an anaerobic osmotic membrane bioreactor

Cytostatic drugs, mainly used as chemotherapy compounds, can pose serious threats to aqueous ecosystem and human health once released into the natural environment. We investigated the use of an anaerobic osmotic membrane bioreactor (AnOMBR) for removing cytostatic drugs from wastewater. The AnOMBR utilizes a dense forward osmosis (FO) membrane in an anaerobic digester with prolonged sludge retention time (60 days). The high rejection of the FO membrane combined with the extended organic retention time in the reactor ensured high removal rates (more than 95.6%) for all the eight cytostatic drugs investigated. With regard to their removal routes in the AnOMBR, the eight cytostatic drugs can be divided into several groups. Doxorubicin, Epirubicin and Tamoxifen were nearly completely removed through the adsorption of anaerobic sludge, while Methotrexate and Cyclophosphamide were mainly removed by biodegradation and FO rejection, respectively. In addition, Mitotane, Azathioprine and Flutamide were removed by both biodegradation and adsorption. This work provides critical insights into the removal mechanisms of high-retention AnOMBRs.

Anaerobic biodegradation and decolorization of a refractory acid dye by a forward osmosis membrane bioreactor

In this study, the feasibility of utilizing an anaerobic osmotic membrane bioreactor (OMBR) for the treatment of a refractory acid dye, Lanaset red G.GR, is demonstrated.

Permeability recovery of fouled forward osmosis membranes by chemical cleaning during a long-term operation of anaerobic osmotic membrane bioreactors treating low-strength wastewater

Anaerobic osmotic membrane bioreactor (AnOMBR) has gained increasing interests in wastewater treatment owing to its simultaneous recovery of biogas and water. However, the forward osmosis (FO) membrane fouling was severe during a long-term operation of AnOMBRs. Here, we aim to recover the permeability of fouled FO membranes by chemical cleaning. Specifically speaking, an optimal chemical cleaning procedure was searched for fouled thin film composite polyamide FO (TFC-FO) membranes in a novel microfiltration (MF) assisted AnOMBR (AnMF-OMBR). The results indicated that citric acid, disodium ethylenediaminetetraacetate (EDTA-2Na), hydrochloric acid (HCl), sodium dodecyl sulfate (SDS) and sodium hydroxide (NaOH) had a low cleaning efficiency of less than 15%, while hydrogen peroxide (H2O2) could effectively remove foulants from the TFC-FO membrane surface (almost 100%) through oxidizing the functional group of the organic foulants and disintegrating the colloids and microbe flocs into fine particles. Nevertheless, the damage of H2O2 to the TFC-FO membrane was observed when a high cleaning concentration and a long duration were applied. In this case, the optimal cleaning conditions including cleaning concentration and time for fouled TFC-FO membranes were selected through confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM) images and the flux recovery rate. The results suggested that the optimal cleaning procedure for fouled TFC-FO membranes was use of 0.5% H2O2 at 25 °C for 6 h, and after that, the cleaned TFC-FO membrane had the same performance as a virgin one including water flux and rejection for organic matters and phosphorus during the operation of AnMF-OMBR.

Microbial electrochemical nutrient recovery in anaerobic osmotic membrane bioreactors

This study demonstrates that by incorporating a microbial electrochemical unit into an anaerobic osmotic membrane bioreactor (AnOMBR), the system addressed several challenges faced by traditional anaerobic membrane bioreactors and recovered biogas, nitrogen, and phosphorus while maintaining high effluent quality with low dissolved methane. The microbial recovery cell (MRC)-AnOMBR system showed excellent organic (>93%) and phosphorus removal (>99%) and maintained effluent COD below 20 mg/L. Furthermore, the reactor effectively recovered up to 65% PO43− and 45% NH4+ from the influent, which can be further improved if membranes with higher selectivity are used. Nutrients removal from bulk solution mitigated NH4+ penetration to the draw solution and reduced scaling potential caused by PO43−. The maximum methane yield was 0.19 L CH4/g COD, and low methane (<2.5 mL CH4/L) was detected in the effluent. Further improvement can be made by increasing charge efficiency for better nutrient and energy recovery.

Development of a novel anaerobic membrane bioreactor simultaneously integrating microfiltration and forward osmosis membranes for low-strength wastewater treatment

Anaerobic osmotic membrane bioreactor (AnOMBR) has aroused growing interests for its low energy demand, ability to efficiently process low ionic strength wastewater and high effluent quality. However, salt accumulation remains a main obstacle for causing severe water flux decline, fouling aggravation and inhibitory on the microbial activity. Here, we report a novel microfiltration (MF) assisted AnOMBR (AnMF-OMBR) for mitigating salt accumulation. The results indicated that the MF membrane effectively prevented salt accumulation in the bioreactor. The stable salinity level (within the range of 2.5–4.0mS/cm) enabled the AnMF-OMBR to achieve a long-term continuous operation together with a higher methane production in comparison with a conventional AnOMBR. The forward osmosis (FO) permeate from the AnMF-OMBR had excellent water quality, while the MF permeate required further treatment (e.g., phosphorus precipitation and activated carbon adsorption) before its beneficial reuse. A thick fouling layer combining biofouling and inorganic scaling was existed on the FO membrane. Further confocal laser scanning microscopy (CLSM) revealed the dominance of polysaccharides and microorganisms over proteins. The current study demonstrated that the AnMF-OMBR can be a promising and sustainable wastewater treatment technology for its simultaneous energy recovery (in the form of biogas) and water reuse (from both FO and MF membranes).

Impacts of inorganic draw solutes on the performance of thin-film composite forward osmosis membrane in a microfiltration assisted anaerobic osmotic membrane bioreactor

A Donnan equilibrium led to a higher NH4+–N concentration and more severe FO biofouling for the draw solutes NaCl and MgCl2, respectively.