Microbial electrolysis cells (MECs) are an electricity-mediated microbial bioelectrochemical technology, which is originally developed for high-efficiency biological hydrogen production from waste ...streams. Compared to traditional biological technologies, MECs can overcome thermodynamic limitations and achieve high-yield hydrogen production from wide range of organic matters at relatively mild conditions. This approach greatly reduces the electric energy cost for hydrogen production in contrast to direct water electrolysis. In addition to hydrogen production, MECs may also support several energetically unfavorable biological/chemical reactions. This unique advantage of MECs has led to several alternative applications such as chemicals synthesis, recalcitrant pollutants removal, resources recovery, bioelectrochemical research platform and biosensors, which have greatly broaden the application scopes of MECs. MECs are becoming a versatile platform technology and offer a new solution for emerging environmental issues related to waste streams treatment and energy and resource recovery. Different from previous reviews that mainly focus on hydrogen production, this paper provides an up-to-date review of all the new applications of MECs and their resulting performance, current challenges and prospects of future.
Display omitted
•Microbial electrolysis cells turning to be versatile technology.•An up-to-date review on recent application possibilities of MECs.•A new platform for waste streams treatment and energy and resource recovery.•Renewable and sustainable power sources are needed to make process cost-effective.•Application oriented reactor design is necessary to lower upscaling costs.
Ammonia and sulfate, which are prevalent pollutants in agricultural and industrial wastewaters, can cause serious inhibition in several biological treatment processes, such as anaerobic digestion. In ...this study, a novel bioelectrochemical approach termed bipolar bioelectrodialysis was developed to recover ammonia and sulfate from waste streams and thereby counteracting their toxicity during anaerobic digestion. Furthermore, hydrogen production and wastewater treatment were also accomplished. At an applied voltage of 1.2 V, nitrogen and sulfate fluxes of 5.1 g NH4+-N/m2/d and 18.9 g SO42−/m2/d were obtained, resulting in a Coulombic and current efficiencies of 23.6% and 77.4%, respectively. Meanwhile, H2 production of 0.29 L/L/d was achieved. Gas recirculation at the cathode increased the nitrogen and sulfate fluxes by 2.3 times. The applied voltage, initial (NH4)2SO4 concentrations and coexistence of other ions were affecting the system performance. The energy balance revealed that net energy (≥16.8 kWh/kg-N recovered or ≥4.8 kWh/kg-H2SO4 recovered) was produced at all the applied voltages (0.8–1.4 V). Furthermore, the applicability of bipolar bioelectrodialysis was successfully demonstrated with cattle manure. The results provide new possibilities for development of cost-effective technologies, capable of waste resources recovery and renewable energy production.
Display omitted
•Novel bipolar bioelectrodialysis for ammonia and sulfate recovery from wastes.•Hydrogen production and wastewater treatment were accomplished along with recovery.•Cathodic gas recirculation increased the nitrogen and sulfate fluxes by 2.3 times.•The system was affected by the voltage, other ions, NH4+ and SO42− concentrations.•Net energy was produced at all the applied voltages between 0.8 and 1.4 V.
A considerable increase in nitrate concentration in groundwater has become a serious concern worldwide. We developed a novel submerged microbial desalination–denitrification cell (SMDDC) to in situ ...remove nitrate from groundwater, produce electric energy, and potentially treat wastewater. The SMDDC, which was composed of an anode and a cathode chamber, can be easily applied to subsurface environments. When current was produced by bacteria on the anode, NO3− and Na+ were transferred into the anode and cathode through anion and cation exchange membrane, respectively; the anode effluent was directed to the cathode where NO3− was reduced to N2 through autotrophic denitrification. For proof-of-concept, the SMDDC was fed with synthetic wastewater as fuel and submerged into a glass reactor filled with synthetic groundwater. The SMDDC produced 3.4 A/m2 of current density, while removing 90.5% of nitrate from groundwater with 12 h wastewater hydraulic retention time (HRT) and 10 Ω of external resistance. The nitrate concentration and ionic strength of groundwater were the main limiting factors to the system performance. Besides, the external resistance and HRT were also affecting the system performance. Furthermore, the SMDDC showed improved performance with high ionic strength of groundwater (2200 μS/cm) and was able to reduce groundwater salinity as well. External nitrification was beneficial to the current generation and nitrate removal rate, but was not affecting total nitrogen removal. Results clearly indicate that this system holds a great potential for efficient and cost-effective treatment of nitrate-containing groundwater and energy recovery.
Display omitted
► An innovative bioelectrochemical system for nitrate removal from groundwater. ► Simultaneous electricity generation, groundwater and wastewater treatment. ► The performance was mainly determined by nitrate concentration and ionic strength. ► High nitrate removal and current generation with high ionic strength groundwater. ► External nitrification was beneficial to current generation and nitrate removal.
Nitrate and nitrite contamination of surface waters (e.g. lakes) has become a severe environmental and health problem, especially in developing countries. The recent demonstration of nitrate ...reduction at the cathode of microbial fuel cell (MFC) provides an opportunity to develop a new technology for nitrogen removal from surface waters. In this study, a sediment-type MFC based on two pieces of bioelectrodes was employed as a novel in situ applicable approach for nitrogen removal, as well as electricity production from eutrophic lakes. Maximum power density of 42 and 36 mW/m2 was produced respectively from nitrate- and nitrite-rich synthetic lake waters at initial concentration of 10 mg-N/L. Along with the electricity production a total nitrogen removal of 62% and 77% was accomplished, for nitrate and nitrite, respectively. The nitrogen removal was almost 4 times higher under close-circuit condition with biocathode, compared to either the open-circuit operation or with abiotic cathode. The mass balance on nitrogen indicates that most of the removed nitrate and nitrite (84.7 ± 0.1% and 81.8 ± 0.1%, respectively) was reduced to nitrogen gas. The nitrogen removal and power generation was limited by the dissolved oxygen (DO) level in the water and acetate level injected to the sediment. Excessive oxygen resulted in dramatically decrease of nitrogen removal efficiency and only 7.8% removal was obtained at DO level of 7.8 mg/l. The power generation and nitrogen removal increased with acetate level and was nearly saturated at 0.84 mg/g-sediment. This bioelectrode-based in situ approach is attractive not only due to the electricity production, but also due to no need of extra reactor construction, which may broaden the application possibilities of sediment MFC technology.
Display omitted
► An innovative approach for nitrate and nitrite removal from eutrophic lakes. ► Eutrophic lakes bioremediation by means of biocathode sediment microbial fuel cell. ► The removal of nitrate and nitrite was enhanced by means of electricity production. ► Main nitrogen removal mechanism was electrochemical denitrification at the cathode. ► DO level and organic matters content were critical to the system performance.
Display omitted
•Novel submersible microbial desalination cell as a new method for ammonia recovery.•In situ lowering ammonia level in anaerobic reactor by ammonia recovery.•Current driven NH4+ ...migration and free NH3 diffusion for ammonia transportation.•Initial ammonia level and external resistance affected the ammonia recovery.•Coexistence of other cations had no negative effect on the ammonia transportation.
High ammonia concentration in anaerobic reactors can seriously inhibit the anaerobic digestion process. In this study, a submersible microbial desalination cell (SMDC) was developed as an innovative method to lower the ammonia level in a continuous stirred tank reactor (CSTR) by in situ ammonia recovery and electricity production. In batch experiment, the ammonia concentration in the CSTR decreased from 6 to 0.7g-N/L during 30days, resulting in an average recovery rate of 80g-N/m2/d. Meanwhile, a maximum power density of 0.71±0.5W/m2 was generated at 2.85A/m2. Both current driven NH4+ migration and free NH3 diffusion were identified as the mechanisms responsible for the ammonia transportation. With an increase in initial ammonia concentration and a decrease in external resistance, the SMDC performance was enhanced. In addition, the coexistence of other cations in CSTR or cathode had no negative effect on the ammonia transportation.
Microbial fuel cells (MFC) have recently received increasing attention due to their promising potential in sustainable wastewater treatment and contaminant removal. In general, contaminants can be ...removed either as an electron donor via microbial catalyzed oxidization at the anode or removed at the cathode as electron acceptors through reduction. Some contaminants can also function as electron mediators at the anode or cathode. While previous studies have done a thorough assessment of electron donors, cathodic electron acceptors and mediators have not been as well described. Oxygen is widely used as an electron acceptor due to its high oxidation potential and ready availability. Recent studies, however, have begun to assess the use of different electron acceptors because of the (1) diversity of redox potential, (2) needs of alternative and more efficient cathode reaction, and (3) expanding of MFC based technologies in different areas. The aim of this review was to evaluate the performance and applicability of various electron acceptors and mediators used in MFCs. This review also evaluated the corresponding performance, advantages and disadvantages, and future potential applications of select electron acceptors (e.g., nitrate, iron, copper, perchlorate) and mediators.
A submersible microbial fuel cell (SBMFC) was developed as a biosensor for in situ and real time monitoring of dissolved oxygen (DO) in environmental waters. Domestic wastewater was utilized as a ...sole fuel for powering the sensor. The sensor performance was firstly examined with tap water at varying DO levels. With an external resistance of 1000Ω, the current density produced by the sensor (5.6±0.5–462.2±0.5mA/m2) increased linearly with DO level up to 8.8±0.3mg/L (regression coefficient, R2=0.9912), while the maximum response time for each measurement was less than 4min. The current density showed different response to DO levels when different external resistances were applied, but a linear relationship was always observed. Investigation of the sensor performance at different substrate concentrations indicates that the organic matter contained in the domestic wastewater was sufficient to power the sensing activities. The sensor ability was further explored under different environmental conditions (e.g. pH, temperature, conductivity, and alternative electron acceptor), and the results indicated that a calibration would be required before field application. Lastly, the sensor was tested with different environmental waters and the results showed no significant difference (p>0.05) with that measured by DO meter. The simple, compact SBMFC sensor showed promising potential for direct, inexpensive and rapid DO monitoring in various environmental waters.
► A new approach for monitoring DO by means of microbial fuel cell technology. ► Microbial mediated current generation as a function of DO levels. ► External resistance and substrate concentration affect the sensor sensitivity. ► Environmental conditions need to be taken into account for sensor calibration. ► Direct, inexpensive and rapid DO monitoring in various environmental waters.
Motion is an important aspect of visual information. The directions of visual motion are encoded in the retina by direction-selective ganglion cells (DSGCs). ON-OFF DSGCs and ON DSGCs co-stratify ...with starburst amacrine cells (SACs) in the inner plexiform layer and depend on SACs for their direction selectivity. J-type retinal ganglion cells (J-RGCs), a type of OFF DSGCs in the mouse retina, on the other hand, do not co-stratify with SACs, and how direction selectivity in J-RGCs emerges has not been understood. Here, we report that both the excitatory and inhibitory synaptic inputs to J-RGCs are direction-selective (DS), with the inhibitory inputs playing a more important role for direction selectivity. The DS inhibitory inputs come from SACs, and the functional connections between J-RGCs and SACs are spatially asymmetric. Thus, J-RGCs and SACs form functionally important synaptic contacts even though their dendritic arbors show little overlap. These findings underscore the need to look beyond the neurons’ stratification patterns in retinal circuit studies. Our results also highlight the critical role of SACs for retinal direction selectivity.
Combined checkpoint blockade (e.g., PD1/PD-L1) with traditional clinical therapies can be hampered by side effects and low tumour-therapeutic outcome, hindering broad clinical translation. Here we ...report a combined tumour-therapeutic modality based on integrating nanosonosensitizers-augmented noninvasive sonodynamic therapy (SDT) with checkpoint-blockade immunotherapy. All components of the nanosonosensitizers (HMME/R837@Lip) are clinically approved, wherein liposomes act as carriers to co-encapsulate sonosensitizers (hematoporphyrin monomethyl ether (HMME)) and immune adjuvant (imiquimod (R837)). Using multiple tumour models, we demonstrate that combining nanosonosensitizers-augmented SDT with anti-PD-L1 induces an anti-tumour response, which not only arrests primary tumour progression, but also prevents lung metastasis. Furthermore, the combined treatment strategy offers a long-term immunological memory function, which can protect against tumour rechallenge after elimination of the initial tumours. Therefore, this work represents a proof-of-concept combinatorial tumour therapeutics based on noninvasive tumours-therapeutic modality with immunotherapy.
•First scaled-up bio-electro-Fenton process for textile wastewater treatment.•High removal efficiency with low electric energy consumption in 20 L reactor.•Identified operating factors that can ...affect treatment performance at pilot-scale.•Successfully validated with six different dyes wastewaters in continuous mode.•Offers insight into development of bio-electro-Fenton process at industrial scale.
Textile wastewater entering natural water bodies could cause serious environment and health issues. Bio-electro-Fenton (BEF) as an efficient and energy saving wastewater treatment technology has recently attracted widespread attention. So far, there is no research available on the scaling-up of BEF process. In this work, an innovative 20 L up-scaled BEF system was constructed for the treatment of methylene blue (MB) containing wastewater. The system was first tested in batch mode. The results showed that the system performance was majorly related to the operating parameters including initial MB concentration, catholyte pH and concentration, cathodic aeration rate, Fe2+ dosage, and applied voltage. At the optimal condition, 20 mg L−1 of MB was efficiently removed following the apparent first order kinetics. The corresponding rate constants for the decolorization and mineralization were 0.68 and 0.20 h−1, respectively. Furthermore, MB decolorization efficiency of 99% and mineralization efficiency of 74% were observed when the hydraulic retention time was 28 h in continuous mode. This work demonstrates the scaling-up potential of BEF for recalcitrant wastewater treatment.
PDF
