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The limited amount of electron mediators (EMs) excreted by microorganisms has restricted electricity generation and the related pollutant removal in microbial fuel cells (MFCs). The polyphenolic-rich plants contain simple polyphenols or anthraquinones that have promising electron-shuttling potential, but this has not been well understood. Herein, four herbal plants Polygonum multiflorum (T. fallopia), rhubarb (B. rheum), radix rubiae (L. Rubia) and semen cassiae (Catsia tora Linn) were selected and then studied to produce EMs to stimulate electricity generation in MFCs. B. rheum had the highest redox activity and 2% acid pretreatment contributing the most to the release of electroactive substances. The highest power density (18.67 W/m3) and Coulombic efficiency (29.03%) and the lowest internal resistance (29.02 Ω) were achieved in MFCs with B. rheum addition compared to other herbal plants. The satisfactory COD (93.68%) and NH4+-N (39.68%) removal were also obtained with a 0.01 g/L dosage. Confocal laser scanning microscopy and high throughput sequencing analysis showed that B. rheum had the least negative effects on biofilm microstructure and microbial species, corresponding to its outstanding performance. These findings first suggested that B. rheum can be regarded as a promising redox mediator to improve MFC performance. This study provided a new thinking to apply herbal wastewater or pharmaceutical waste in improving the bioelectrochemical system.

Soil microbial fuel cells (MFCs) have been applied for the in situ remediation of soils polluted by single antibiotics. However, the investigation of only single antibiotic pollution has hindered MFC application in real-world soil remediation, where the effects of multiple antibiotics with similar chemical structures on the fate of antibiotics and their corresponding antibiotic resistance genes (ARGs) remain unknown. In this study, antibiotic removal rates, microbial community compositions, metabolite compositions, and ARG abundances were investigated in soil MFCs by adding two commonly used antibiotics (sulfadiazine, SDZ, and sulfamethoxazole, SMX), and comparing them with the addition of only a single antibiotic (SDZ). The antibiotic removal rate was higher in the soil MFC with addition of mixed antibiotics compared to the single antibiotic due to enhanced biodegradation efficiency in both the upper (57.24% of the initial antibiotic concentration) and lower layers (57.07% of the initial concentration) of the antibiotic-polluted soils. Bacterial community diversity in the mixed antibiotic conditions increased, and this likely resulted from the decreased toxicity of intermediates produced during antibiotic biodegradation. Moreover, the addition of mixed antibiotics led to lower risks of ARG release into soil environments, as reflected by higher abundances of host bacteria in the single antibiotic treatment. These results encourage the further development of soil MFC technology for in situ remediation of antibiotic-polluted soils.

Osmotic membrane bioreactors (OMBRs) have been applied to enhance removal of antibiotics, however, information on the effects of molecular structures on the behavior of antibiotics is still lacking. Herein, adsorption kinetics, transformation pathways, and membrane rejection mechanisms of OMBRs were investigated by adding two typical antibiotics (i.e., sulfadiazine, SDZ, and tetracycline hydrochloride, TC-HCl). 80.70–91.12% of TC-HCl was removed by adsorption and biodegradation, while 17.50–75.14% of SDZ was removed by membrane rejection; this depended on its concentration due to reduced electrostatic interactions and hydrophobic adsorption. The adsorption capacity of TC-HCl (i.e., 1.34±0.01 mg/g) was significantly higher than that of SDZ (i.e., 0.18±0.03 mg/g) due to enhanced π-π interactions, hydrogen bonding and improved electrostatic interactions. The abundant production of polysaccharide-like substances from TC-HCl biodegradation contributed to microbial metabolism and thus enhanced microbial function during TC-HCl biotransformation. The primary degradation pathways were determined by microbial function analysis, and the primary intermediates from TC-HCl degradation were less toxic than those from SDZ degradation due to the different reactions of amino groups. These results and the corresponding mechanism provide a theoretical foundation for the further development of OMBR technology for highly efficient treatment of antibiotic wastewater.

Nitrogen removal in osmosis membrane bioreactor (OMBR) is important to its applications but remains a challenge. In this study, a bioelectrochemically-assisted (BEA) operation was integrated into the feed side of OMBRs to enhance nitrogen removal, and sodium acetate was served as a draw solute and supplementary carbon source for the growth of denitrifying bacteria due to reversed-solute. The effects of operation mode and influent ammonium (NH4+) concentration were systematically examined. Compared to a conventional OMBR, the integrated BEA-OMBR achieved higher total nitrogen removal efficiency of 98.13%, and chemical oxygen demand removal efficiency of 95.83% with the influent NH4+-N concentration of 39 mg L−1. The sequencing analyses revealed that ammonia-oxidizing bacteria (0–0.04%), nitrite-oxidizing bacteria (0–0.16%), and denitrifying bacteria (1.98–8.65%) were in abundance of the microbial community in the feed/anode side of integrated BEA-OMBR, and thus BEA operation increased the diversity of the microbial community in OMBR. Future research will focus on improving nitrogen removal from a high ammonium strength wastewater by looping anolyte effluent to the cathode. These findings have demonstrated that BEA operation can be an effective approach to improve nitrogen removal in OMBRs toward sustainable wastewater treatment.

In this study, a microbial fuel cell coupled with constructed wetland (CW-MFC) was built to demonstrate that integration of MFC can enhance antibiotics (sulfadiazine (SDZ) and ciprofloxacin (CIP)) removal in CWs and control CH4 emissions. Better COD and antibiotics removal performance was obtained in CW-MFC. Notably, both reactors can remove more than 90.00% of CIP. A decline in methane fluxes (by 15.29%) was also observed in CW-MFC compared with CW. The presence of Acorus tatarinowii had no obvious effect on antibiotics removal but the application of manganese ore substrate reduced methane emissions. Further study showed that Proteobacteria was enriched on the Mn substrate anode and the relative abundance of Methanothrix was declined. The results suggested that suppression of methanogenesis may be contributed to a low methane flux in CW-MFC. This study will facilitate the application of CW-MFC to treat antibiotics wastewater and control the ecological risks of greenhouse gas emissions.

Salinity accumulation in osmotic membrane bioreactors (OMBRs) is one of the key challenges, which can be mitigated in situ by reverse-fluxed solute transport through integration of bioelectrochemical systems (BES). The effects of several key operating parameters on salinity accumulation were investigated. Salinity accumulation depended on balance between reversal solute flux (RSF) and reverse-fluxed ammonium (RFA) transport, which was driven by electrical migration and concentration diffusion. DS concentration was the primary factor influencing RSF, and the lowest DS concentration exhibited the minimum solute leakage. Aeration played a vital role in RFA transport, and a higher aeration helped to enhance RFA transport. Increased current generation (i.e., influent flow rate of 0.5 mL min−1 and external resistance of 5.0 Ω) contributed to RFA migration. The lack of electrolyte addition in catholyte contributed to RFA diffusion. These optimal parameters encourage the further development of an effective strategy for salinity mitigation in BES-based OMBR technology.

Reverse solute flux (RSF) is a key challenge for operating osmotic membrane bioreactors (OMBRs) and can severely affect the OMBR performance due to solute accumulation in the feed side. Herein, a biodegradable polyelectrolyte (polyacrylic acid sodium salt, PAA) was investigated as a draw solute (DS) for OMBR application with a focus on the mitigation of solute build-up via biodegradation of PAA. Both activated sludge and OMBR tests confirmed that PAA can be biologically degraded. In the OMBR, a residue PAA concentration of 14.1 mg L−1 was observed in the feed solution due to a dynamic balance between PAA removal/biodegradation and continuous RSF. Compared to a non-biodegradable DS (NaCl) that had a water recovery of 3.4 ± 0.1 L and a reverse solute flux (RSF) of 9.46 ± 0.21 gMH, the PAA DS achieved a higher water recovery of 17.9 ± 0.5 L over 30 days of operation (the average water flux, 4.97 ± 0.14 LMH), a much lower RSF of 0.12 ± 0.01 gMH, and a higher nitrogen removal of 58.4 ± 1.5%. The recovery and reuse of the PAA DS were investigated with a long-term operation (150 days), which demonstrated the feasibility of reusing the PAA DS, despite some decrease in water recovery and biological treatment performance. Those results have collectively demonstrated the advantages of the PAA-based draw solute for reducing reverse-fluxed solutes towards optimized OMBR operation and applications.

Few studies have evaluated sulfadiazine (SDZ) removal and the potential risks of antibiotic resistance gene (ARG) accumulation in up-flow microbial fuel cell coupled constructed wetlands (UCW-MFCs). This study aims to investigate the removal of SDZ, accumulation of ARGs (sulI, sulII, intI), and bacterial community changes in four UCW-MFC reactors with two hydraulic retention times (HRTs) and two circuit operation modes. The results indicated that effluent from a closed circuit UCW-MFC had a lower SDZ concentration due to a higher electrode absorption capacity for SDZ and the dehydrogenase activity of the bacteria. Additionally, the ARG abundance in closed circuit system was higher than that in open circuit system. A lower HRT was correlated with a higher SDZ concentration accumulation on the electrode, which led to a higher ARG abundance. Also, an obvious increase in the ARG abundance was observed during treatment periods. The relative abundance of target ARGs in the anode was higher than in the cathode and the bottom. A cluster analysis of bacterial communities at the phyla level showed they were more significantly affected by HRT. Furthermore, a closed circuit system and a high HRT contributed to high microbial diversity. In addition, five phyla of bacteria might be potential hosts for ARGs. Enrichment of ARG potential hosts induced by SDZ may be responsible for ARG abundance increase. Electricity production characteristics of the UCW-MFCs were also affected by HRT.

Osmotic microbial fuel cells (OsMFCs) combine the merits of microbial fuel cell (MFC) and forward osmosis (FO) for simultaneous contaminant removal, electricity generation, and high-quality water extraction. As an FO based technology, reverse solute flux (RSF) is one of the key challenges for its operation. Herein, RSF was converted into a positive effect on the system performance by using NaHCO3 solution as a draw solution (DS)/catholyte. It was found that reverse-fluxed NaHCO3 helped buffer the anolyte pH and thus enhance electricity generation, compared to the OsMFC using the NaCl DS/catholyte. At the same concentration, the NaHCO3 DS/catholyte achieved a higher Coulomb production of 1349.2 ± 80.3 C and higher anolyte pH of 6.48 ± 0.19 than those of the NaCl DS/catholyte. At the same conductivity, the NaHCO3 DS/catholyte exhibited better electricity generation performance with a comparable recovered water volume of 417.7 ± 13.7 mL to that of the NaCl DS/catholyte. As the NaHCO3 concentration increased from 0.1 M to 0.75 M, the OsMFC electricity generation was enhanced due to the increased RSF from 19.2 ± 2.3 to 210.8 ± 17.5 mmol m−2h−1. In the anode, 92.0 ± 0.8% to 97.1 ± 0.9% of reverse-fluxed NaHCO3 was used to neutralize protons. These results have demonstrated a new strategy that uses the bicarbonate migration driven by both a concentration gradient and electricity generation to successfully raise the alkalinity of the anolyte towards enhancing electricity generation.

A continuous flow microbial fuel cell constructed wetland (MFC-CW) coupled with a biofilm electrode reactor (BER) system was constructed to remove sulfamethoxazole (SMX). The BER unit powered by the stacked MFC-CWs was used as a pretreatment unit, and effluent flowed into the MFC-CW for further degradation. The experimental results indicated that the removal rate of 2 or 4 mg/L SMX in a BER unit was nearly 90%, and the total removal rate in the coupled system was over 99%. As the hydraulic retention time (HRT) was reduced from 16 h to 4 h, the SMX removal rate in the BER decreased from 75% to 48%. However, the total removal rate in the coupled system was still over 97%. The maximum SMX removal rate in the MFC-CW, which accounted for 42%–55% of the total removal, was obtained in the anode layer. In addition, the relative abundances of sul genes detected in the systems were in the order of sulI > sulII > sulIII, and significant positive correlations of sul gene copy numbers versus SMX concentration and 16S rRNA gene copy numbers were observed. Furthermore, significant negative correlations were identified between sul genes, 16S rRNA gene copy numbers, and HRT. The abundances of the sul genes in the effluent of the MFC-CW were lower than the abundances observed in the BER effluent. High-throughput sequencing revealed that the microbial community diversity of the BER was affected by running time, power supply forms and HRT. Bio-electricity from the MFC-CW may reduce microbial community diversity and contribute to reduction of the antibiotic resistance gene (ARG) abundance in the BER. Taken together, the BER-MFC-CW coupled system is a potential tool to treat wastewater containing SMX and attenuate corresponding ARG abundance.

The intensive use of antibiotics results in their continuous release into the environment and the subsequent widespread dissemination of antibiotic resistance genes (ARGs), thus posing potential risks for public health. Although vertical up-flow constructed wetlands (VUF-CWs) have been widely used to treat wastewater in remote or rural regions, few studies have assessed the potential risks of ARG dissemination when VUF-CWs are applied to treat wastewaters containing antibiotics. In this study, the removal performance of two typical antibiotics (sulfamethoxazole (SMX) and tetracycline (TC)) and the fate of ARGs were evaluated in three lab-scale VUF-CWs. The results indicated that high removal efficiencies (>98%) could be achieved for both SMX and TC. However, the exposure of antibiotics resulted in harboring abundant ARGs (mainly sul- and tet-related genes), even with increasing abundances with operation time. The abundances of ARGs had a positive correlation with the accumulation of SMX and TC in different layers of VUF-CWs, where the tet and sul genes have the highest abundance in the bottom layer due to the highest antibiotic exposure concentration. Positive correlations were observed between the abundance of tet gene and antibiotic concentration in effluent. Although the effluent had lower abundances of the ARGs than that in the wetland media, the occurrence of ARGs in effluent might still pose risk for public health. Further studies are required to explore effective control strategies to eliminate ARGs from VUF-CWs.

Forward osmosis (FO) technology has long been constrained by the slow development of appropriate draw solutes (DS) and the relatively high cost associated with DS recovery. In this study, a series of polyelectrolytes, polyacrylic acid sodium salts (PAA-Na) with different molecular weights, were explored as DS for FO applications with a focus on the recovery using combined pH and microfiltration (MF). The FO system achieved a high water flux of 18.02 ± 0.51 LMH, low reverse salt flux (RSF) of 0.110 ± 0.004 gMH, and the J S / J W of 6.1 ± 0.3 mg L − 1 with 25 wt% PAA-Na (2000 Da) as the DS and DI water as the feed. The DS recovery efficiency by the combined pH + MF approach was 99.68% at pH of 4.35, and the operation cost was estimated at 0.037 $ m − 3 . Dynamic light scattering revealed that the hydrodynamic diameter of PAA increased with decreasing pH, resulting in PAA polymers precipitated as aggregates at the pH response point. The 25 wt% 2000 PAA-Na achieved the water flux of 11.56 ± 0.32 LMH from synthetic seawater and 17.19 ± 0.52 LMH from the treated wastewater. These results have demonstrated efficient and cost-effective recovery of PAA DS for FO-based applications.

A bioelectrochemical system (BES) containing membrane-aerated nitritation-anammox in its cathode has been developed for enhancing nitrogen removal. Long-term performance and microbial community structure were investigated. The BES using loop operation and external voltage achieved the highest total nitrogen removal efficiency of 94.8±7.7%, and COD removal of 98.2±3.3% at hydraulic retention time of 60h and the lumen pressure of 10psi. The energy consumption of the system was 0.90kWhkgN-1 or 0.38kWhkg COD-1. Sequencing analyses revealed that ammonia oxidizing bacteria (0.2-7.4%), anammox bacteria (0.4-10.3%), denitrifying bacteria (5.8-13.1%), and electrogenic bacteria (4.6-12.8%) were in abundance of the microbial community in the cathode chamber, and their distributions were affected by the aeration and physical locations. These results encourage further investigation of membrane-aerated nitritation-anammox in BES for optimization and potential applications with actual wastewater.

Microbial electrolysis cells (MECs) are a promising approach for producing hydrogen gas from low-grade substrates with low energy consumption. However, pH increase in a cathode due to proton reduction and thus the need for buffering this pH increase remains a challenge for MEC operation. In this study, a previously reported operational strategy for pH buffer - periodic polarity reversal (PPR) was further studied by developing and applying an automatically control system. The effect of PPR interval on the hydrogen production was investigated and the optimal PPR interval was determined. With an optimal PPR interval of 40 min, the MEC had a significantly low pH increase rate of 0.0085 min −1 in its cathodes, and this resulted in the highest current density of 1.58 ± 0.02 A m −2 , Coulombic efficiency of 130.3 ± 1.8%, hydrogen production rate of 1.65 ± 0.01 m 3 H 2 m −3 d −1 , overall hydrogen recovery of 75.9 ± 0.4%, and energy efficiency relative to the substrate input of 140.8 ± 1.4%. Further analysis suggested that this optimal value of PPR interval was affected by both reaction time and hydrogen supply. When the PPR interval increased from 10 min to 40 min, a longer reaction time helped produce more protons and thus generated a stronger buffer capacity. Beyond 40 min, the mass transfer of the dissolved hydrogen gas could become a limiting factor, leading to a weaker buffer capacity with a longer PPR interval. Those findings have provided an effective pH control strategy with a convenient control system for maximizing hydrogen production in MECs.

Successful pH control plays a key role in hydrogen production in microbial electrolysis cells (MECs). Herein, periodic polarity reversal (PPR) is applied to a dual-cathode MEC and achieves the enhanced hydrogen production. The MEC with PPR produces 1.3 ± 0.1 m 3 H 2 m −3 d −1 with 50-mM NaCl as the catholyte, much higher than 0.9 ± 0.1 m 3 H 2 m −3 d −1 from the MEC with dual-working cathodes or 0.8 ± 0.1 m 3 H 2 m −3 d −1 from the MEC with one working cathode. Such enhancement benefits from a slower increase in the catholyte pH, for example, it takes 15.3 h to increase the 10-mM NaCl pH from 7.00 to 12.00 in the MEC with PPR, 1.7–3.6 times that of the MECs without PPR, which is due to the decrease in the catholyte pH of the reversed cathode during PPR. The potential of the reversed electrode is more positive than the anode, suggesting that the reversed electrode acts as a second anode electrode using residue hydrogen gas as an electron source. Thus, a mechanism of in situ oxidation of hydrogen gas for pH buffering is proposed and discussed. These findings have provided a simple but effective pH control strategy for enhancing hydrogen production in MECs.

Objective: We assessed clinical effectiveness, longevity of treatment effects, and patient satisfaction with incobotulinumtoxinA for glabellar frown lines (GFL) treatment in Asian patients. Design, Setting, and Participants: This was a prospective, multicenter, single-arm, open-label study at six sites in Taiwan. Patients aged 20 to 65 years with mild to very severe GFLs (Merz scale: 1–4 points) were eligible; 45 patients [including 23 BoNT/A-naïve and 22 previously-treated (“switch”) patients were enrolled. Patients received intramuscular incobotulinumtoxinA injection at up to five injection points. Total doses ranged from 12 to 20U. Measurements: Investigators assessed improvements in dynamic GFLs at Days 14 and 120 using the validated five-point Merz scale (0=no lines; 4=very severe lines). Treatment satisfaction was self-reported by patients via questionnaire. Results: All patients showed excellent response to treatment in that Merz scores at Day 14 were 0 or 1 point(s). Both groups showed a mean improvement of 2.9 points; the response rate (1-point improvement or more from baseline) was 100 percent. GFL improvement was maintained over at least four months in both groups (mean improvements at Day 120: 1.5 points, naïve; 1.7 points, switch). Patient satisfaction ratings remained high (almost 100% in both groups) throughout the study. There were no statistically significant differences between groups regarding treatment satisfaction or GFL improvement (Merz score) at Days 14 and 120. No adverse events occurred. Conclusion: In Asian patients, incobotulinumtoxinA treatment for dynamic GFLs is effective and long lasting, with no expected differences between BoNT/A-naïve patients and those switching from other BoNT/As. IncobotulinumtoxinA yields consistent and natural-looking results for first and subsequent treatments.

Economic development and the related increase in global energy demands have created pressure on the supply of energy resources. To promote sustainable development, a safe and renewable ener...

Three-dimensional biofilm electrode reactors (3D-BERs) with high treatment efficiency were constructed to treat wastewater containing sulfadiazine (SDZ) and ciprofloxacin (CIP) coexposure with Zinc (Zn). The results showed that coexposure to target antibiotics and Zn increased the absolute and relative abundances of target antibiotic resistance genes (ARGs). Additionally, the target ARG abundances were higher on cathode of 3D-BER compared with ordinary anaerobic reactor while the abundances of total ARGs were decreased in the effluent. Meanwhile, redundancy analysis results revealed that the composition of bacteria carrying ARGs was greatly influenced in the cathode by the accumulation of Zn and antibiotic, which dominated the changes of ARG abundances. Additionally, ARGs with their host bacteria revealed by network analysis were partially deposited on electrode substrates when being removed from wastewater. Thus, 3D-BER exhibits capability of simultaneously eliminating antibiotic and Zn, and greatly reduces the risks of ARGs spread.

A suitable draw solute (DS) concentration in bioelectrochemically assisted osmotic membrane bioreactor (BEA-OMBR) can convert the “negative effect” of salinity accumulation into a “beneficial effect” by using the reverse-fluxed DS as a buffer agent or a carbon source supplement. Herein, the effect of DS concentration from acid buffer solution (i.e., ammonium chloride, NH4Cl), alkaline buffer solution (i.e., sodium bicarbonate, NaHCO3), and organic solution (i.e., sodium acetate, NaOAc) on salinity accumulation was systematically investigated. Salinity accumulation with NaHCO3 DS mainly derived from reversal fluxed sodium ion (Na+, major contributor with DS concentration ≤0.25 M) and bicarbonate ion (main contributor with DS concentration ≥0.50 M): Na+ accumulation could be mitigated by Na+ transport dominant by electrically driven migration (i.e., 21.3–62.1% of reverse-fluxed Na+), and bicarbonate accumulation could be reduced by buffer system. A medium-low concentration of 0.25 M NH4Cl DS had a better performance on current density of 165.0 ± 23.0 A m−3 and COD removal efficiency of 91.5 ± 3.4% by taking advantage that 77.7 ± 1.3% of reverse-fluxed ammonium could be removed by biological treatment and ammonium transport. A high NaOAc DS concentration (i.e., ≥0.05 M) exhibited a higher current density of 145.3–146.0 A m−3 but a lower COD removal efficiency due to the limited carbon source utilization capacity of anaerobic bacteria. Both concentration diffusion (20.9–28.3%) and electrically driven migration (29.5–39.4%) promoted reverse-fluxed Na+ transport to catholyte and thus mitigated Na+ accumulation in the feed/anolyte. These findings have provided an optimal DS concentration for BEA-OMBR operation and thus encourage its further development.

The goal of this research was to investigate the performance of constructed wetlands (CWs) for the removal of dissolved organic carbon (DOC) and access the possible, formation of disinfection by-products (DBPS) after CWs treatment. A mixture of raw water from Yangtze River was spiked directly into pilot-scale CWs to assess impacts on various factors, including the removal of DOC, ultraviolet absorbance at 254 nm (UV254), specific ultraviolet Absorbance (SUVA), disinfection by-products formation potential (DBPFP), trihalomethane formation potential (THMFP), and haloacetic formation potential (HAAFP). The average removal of CODMn, NH4+-N, TN, DOC, UV254, THMs, and HAAs were 38.40%, 41.70%, 25.90%, 30.96%, 47.58%, −20.52%, and 25.22% respectively. CWs could degrade complicated organic matter into those with lower molecular weight, but could not further change to carbon dioxide and water. The average molecular weight of THMs in effluent flow declined to the level below, and high molecular weight organic compounds were more likely to form HAAs. The SUVA had no obvious relationships with the removal of specific trihalomethane formation potential (STHMFP), but had apparent relationship with the removal of specific haloacetic formation potential (SHAAFP) in CWs (p

Hybrid osmotic membrane bioreactor (OMBR) takes advantage of the cooperation of varying biological or desalination processes and can achieve NEWS (nutrient-energy-water-solute) recovery from wastewater. However, a lack of universal parameters hinders our understanding. Herein, system configurations and new parameters are systematically investigated to help better evaluate recovery performance. High-quality water can be produced in reverse osmosis/membrane distillation-based OMBRs, but high operation cost limits their application. Although bioelectrochemical system (BES)/electrodialysis-based OMBRs can effectively achieve solute recovery, operation parameters should be optimized. Nutrients can be recovered from various wastewater by porous membrane-based OMBRs, but additional processes increase operation cost. Electricity recovery can be achieved in BES-based OMBRs, but energy balances are negative. Although anaerobic OMBRs are energy-efficient, salinity accumulation limits methane productions. Additional efforts must be made to alleviate membrane fouling, control salinity accumulation, optimize recovery efficiency, and reduce operation cost. This review will accelerate hybrid OMBR development for real-world applications.

By combining the merits of bioelectrochemical systems and osmotic membrane bioreactors (OMBRs), bioelectrochemically assisted OMBRs (BEA-OMBRs) can achieve simultaneous water/electricity recovery and salinity mitigation. One of the key challenges is reverse solute flux (RSF). The “negative effect” of RSF was turned into a “beneficial effect” by using a reverse-fluxed draw solute (DS) as a buffering agent or a carbon source supplement. The reverse-fluxed anions from the alkaline buffering DSs (NaHCO3 and PBS) stabilized the anolyte pH and had a positive effect on system performance, such as a high total Coulomb of 278.16–289.80C, a high recovered water of 261.64–277.80 mL, and a high COD removal of 90.91–91.61%. The reverse-fluxed cations from the acidic buffering DS (NH4Cl) promoted the accumulated ammonium to diffuse from the feed/anode to the cathode side due to the production of ammonia gas in the alkaline catholyte. The organic DS exhibited a lower RSF and a lower anolyte conductivity of 5.12–8.49 mS cm−1. However, the reverse-fluxed organic DSs (glucose and NaOAc) had a negative effect on the electricity generation due to carbon source competition. These results have demonstrated the advantages of the reverse-fluxed DS to enhance the system performance and to encourage further development of BEA-OMBR technology.

Given its advantages in terms of high efficiency and low energy consumption, bioelectrochemical system (BES) has been applied widely in the removal of various antibiotics from wastewater. BES avoids the proliferation of antibiotic resistance genes (ARGs) by producing less amount of sludge compared with wastewater treatment plants. However, transmembrane permeability and membrane potential can be affected by the electrical stimulation, resulting in increases in the antibiotic-resistant bacteria (ARB) and ARGs in BES. Based on limited published works available, the main objective of this review is to summarize the applications of BES for antibiotic removal and the fate of ARB and ARGs in such systems. Antibiotics can be effectively removed by BES. However, low electric current promotes vertical and horizontal ARGs transfer during the treatment of antibiotics in BES. Promisingly, ARB and ARGs could be inhibited by a higher electric current. This study raises questions regarding the potential role of BES in antibiotic removal and the consequent fate of ARGs and ARB in wastewater.

Sulfamethoxazole (SMX) pollution in wastewater threatens public health. A novel membrane bioelectrochemical reactor (MBER) with loop operation was developed for SMX degradation in low-C/N ratio wastewater. A gas-permeable silicone membrane module was used to precisely control the dissolved oxygen in the catholyte and save energy. Compared with a traditional membrane bioreactor (i.e., open-circuit reactor), the removal of SMX was increased from 49.91% to 71.10% in the proposed MBER (i.e., closed-circuit reactor). Sequencing analyses revealed that SMX was removed via cometabolism with NH4+-N and COD removal in both the anode and cathode chambers. Six intermediates were detected as degradation products in the cathodic effluent; these intermediates pose a similar potential threat to the environment as SMX. Two possible degradation pathways, deduced from the sequencing analyses and degradation products, were proposed. These results provide a new technology for improving SMX removal through the integration/coupling of bioelectrochemical technology into a membrane bioreactor.

Microbial fuel cell constructed wetlands (CW-MFCs) with different circuit operation conditions and hydraulic retention time (HRT) were constructed to evaluate their ability to remove and accumulate pharmaceutical and personal care products (PPCPs) (sulfadiazine (SDZ), carbamazepine (CBZ), naproxen (NPX) and ibuprofen (IBP)) during four months running process. The abundance level of corresponding sulfonamide antibiotic resistance genes (ARGs) was also investigated. The results showed that closed circuit operation of CW-MFC contributed to the decrease in mass loading of COD, NH4+-N, PPCPs, and wastewater toxicity in the effluent. Additionally, closed circuit operation with low HRT contributed to enhancing selected PPCP mass accumulation on electrodes by electro-adsorption, and thus the higher sulfonamide ARG abundance was detected in the electrodes and effluent. Moreover, the composition of bacteria was greatly influenced by the mass accumulation of PPCPs revealed by redundancy analysis results. Procrustes analysis results further demonstrated that bacterial community contributed greatly to the ARGs profiles. Therefore, ARGs with their host bacteria revealed by network analysis were partially deposited on electrode substrates, and thus ARGs were effectively accumulated on electrodes. Function analysis of the bacterial community from PICRUSt predicted metagenomes revealed that closed circuit mode enhanced the abundances of the function genes of metabolic and the multiple ARGs, suggesting that closed circuit operation exhibited positive effects on metabolic process and ARG accumulation in CW-MFC system.

This study aims to demonstrate that an up-flow microbial fuel cell-coupled constructed wetland (UCW-MFC) can effectively treat synthetic wastewater that contains a high concentration of pharmaceutical and personal care products (PPCPs, 10 mg L−1 level), such as ibuprofen (IBP) and bisphenol A (BPA). A significant decline in chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N) removal was observed when BPA was added, which indicated that BPA was more toxic to bacteria. The closed circuit operation of UCW-MFC performed better than the open circuit mode for COD and NH4+-N removal. Similarly, the removal rates of IBP and BPA were increased by 9.3% and 18%, respectively, compared with the open circuit mode. The majority of PPCPs were removed from the bottom and anode layer, which accounted for 63.2–78.7% of the total removal. The main degradation products were identified. The removal rates of IBP and BPA decreased by 14.6% and 23.7% due to a reduction in the hydraulic detention times (HRTs) from 16 h to 4 h, respectively. Electricity generation performance, including voltage and maximum power density, initially increased and then declined with a decrease in the HRT. Additionally, both the current circuit operation mode and the HRT have an impact on the bacterial community diversity of the anode according to the results of high-throughput sequencing. The possible bacterial groups involved in PPCP degradation were identified. In summary, UCW-MFC is suitable for enabling the simultaneous removal of IBP and BPA and successful electricity production.

Pollution by antibiotics and antibiotic resistance genes has become a major health concern. A microbial fuel cell coupled constructed wetland (CW-MFC) is a new installation to simultaneously treat wastewater and produce energy. This study was conducted to assess the removal efficiency of tetracycline (TC) and sulfamethoxazole (SMX) and the development of TC and SMX resistance genes (tetA, tetC, tetO, tetQ, tetW, sulI and sulII) in the CW-MFCs. At the same time, electricity was also produced during the co-metabolism of the antibiotics and glucose. The results indicated that the CW-MFCs could significantly reduce the concentration of TC and SMX in wastewater. Accumulation of antibiotics and the relative abundances of the tet and sul genes in different layers of the CW-MFCs were: anode layer > cathode layer > middle layer > effluent. The relative abundances of ARGs in the substrates ranged from 1.40 × 10−4 to 6.30 × 10−1 for tet genes and 5.58 × 10−3 to 9.27 × 10−2 for sul genes. The relative abundances of the tetC, tetQ, TetW, sulI and sulII genes were significantly affected by the antibiotics in effluent of the CW-MFCs. In addition, the highest power density obtained under the external resistance of 1000 Ω was 0.0578 W m−2. However, an obvious drop of power density was observed when the antibiotic concentrations increased from 400 to 1600 μg L−1.

A previous study revealed that the electrolytic stimulation process in bio-electrochemical reactors (BER) can accelerate growth of sulfadiazine (SDZ) antibiotic resistant bacteria (ARB) in nutrient broth medium. However, the influence of different medium nutrient richness on the fate of ARB and the relative abundance of their corresponding antibiotic resistance genes (ARGs) in this process is unknown. Specifically, it is not clear if the fate of ARB in minimal nutrition simulated wastewater is the same as in nutrient broth under electrolytic stimulation. Therefore, in this study, nutrient broth medium and the simulated wastewater were compared to identify differences in the relative abundance of Klebsiella michiganensis LH-2 ARGs in response to the electrolytic stimulation process, as well as the fate of the strain in simulated wastewater. Lower biomass, specific growth rates and viable bacterial counts were obtained in response to the application of increasing current to simulated wastewater medium. Furthermore, the percentage of ARB lethality, which was reflected by flow cytometry analysis, increased with current in the medium. A significant positive correlation of sul genes and intI gene relative abundance versus current was also observed in nutrient broth. However, a significant negative correlation was observed in simulated wastewater because of the higher metabolic burden, which may have led to decreased ARB viability. Further investigation showed that the decrease in ARGs abundance was responsible for decreased strain tolerance to SDZ in simulated wastewater. These results reveal that minimal nutrition simulated wastewater may reduce ARB and ARGs propagation in BER.

A key challenge for osmotic membrane bioreactors (OMBRs) application is reverse solute flux and consequent salt accumulation in the feed side. Herein, a bioelectrochemical system (BES) was employed to drive reverse-fluxed solutes from the feed of an OMBR into a cathode compartment for recovery and subsequent reuse as a draw solute (DS). Compared to an OMBR without BES function, the present OMBR system enhanced water recovery from 925 to 1688 mL and increased the chemical oxygen demand (COD) removal efficiency from 40.2 ± 8.1 to 75.2 ± 3.3%, benefited from its lower anolyte conductivity of 9.0 mS cm−1 than that of the control system (24.1 mS cm−1). The CO2 addition significantly improved the ammonia recovery rate to 93.3–116.7 g N m−3 h−1 (or 248.0–307.4 g N m−2 d−1), 12.1–14.5 times higher than that without CO2 addition. The recovered DS was successfully applied to accomplish water extraction in the reuse test, and such a recovery/reuse process could result in a normalized water recovery of 3870 mL mol DS−1 or a DS usage of 0.26 mol L−1 (of the recovered water). The energy consumption of the system might be compensated by the production of bioenergy, and the net specific energy consumption was estimated to be 0.004–0.112 kWh m−3 wastewater, 0.007–0.179 kWh kg−1 removed COD, or 0.001–0.020 kWh kg−1 recovered NH4+-N. Those results have demonstrated that bioelectrochemical processes can be an effective approach for in situ mitigation of reverse-fluxed solute in OMBR and recovering “the lost DS” towards both reuse and reduced operational expense.

The aim of this work was to study reverse solute flux (RSF) from osmotic membrane bioreactor (OMBR) and consequent solute buildup in the feed side. A polyelectrolyte (PAA-Na) served as a draw solute (DS) to minimize RSF in OMBRs. In addition, a bioelectrochemical system (BES) was employed to drive accumulated cations from the feed/anode side into the cathode compartment, subsequently achieving PAA-Na DS recovery with the aid of high catholyte pH. Compared to the 1 M NH4HCO3 DS, the 0.48 g mL−1 PAA-Na DS produced consistently stable water flux, enhanced water recovery and increased ammonium removal efficiency. Due to a dynamic balance between PAA removal and continuing RSF, the residual PAA concentration was 72 mg L−1 on the feed side (27.0% of TOC). These results demonstrate the advantages of integrating a PAA-Na DS with a BES to mitigate RSF and to support further development of OMBR technology.