Anode Effluent Research Articles

Electrochemical conversion of methane measured by anode out gas monitoring over Ce-Co-Cu anode electrocatalysts

Abstract Solid oxide fuel cells (SOFCs) enable the highly efficient conversion of fuels to electricity, offering notable fuel flexibility. However, conventional nickel-based SOFC anode materials currently available on the market are unable to effectively utilise low-carbon fuels without succumbing to carbon deposition, which degrades the anode rapidly. This study introduces a nickel-free SOFC anode electrocatalyst capable of achieving impressive power densities exceeding 400 mW·cm-2 at 850˚C when operating directly with pure methane. Comparative analysis of three cell types, each with varying amounts of ceria, cobalt, and copper in their anode compositions, was conducted. Gas chromatography was employed to monitor anode effluent gases under electrochemical conditions, complemented by electrochemical impedance assessments using hydrogen as the fuel to identify polarisation sources within these innovative anode configurations.
The findings reveal that tracking chemical and electrochemical reactions in SOFCs provides insights into efficiency and fuel conversion mechanisms, wherein the anode material transforms fuel into useful products while generating electricity and heat. Notably, copper additions influence these behaviours, although Cobalt-rich catalysts exhibit superior performance in facilitating fuel conversion through combined electrochemical and thermochemical reactions. Distribution of relaxation times analysis highlights the necessity of optimising microstructure and mitigating gas diffusion polarisation effects, corroborating the validity of equivalent circuit models aligned with electrochemical impedance spectroscopy data.

Modeling Hydrogen Crossover in Proton Exchange Membrane Water Electrolyzers with and without Recombination Catalyst Interlayers

Low-temperature proton exchange membrane water electrolyzers (PEMWEs) are poised to undergo rapid expansion in the coming decades for clean hydrogen production. Hydrogen has been hailed as the ‘Swiss Army knife’ of decarbonization as it can help mitigate carbon dioxide emissions from ammonia production, metal refining, and heavy-duty vehicle transportation. Proliferation of clean hydrogen production necessitates large reductions in iridium loadings in the anode while also operating at higher current density values. The latter goal can be achieved by adopting thinner proton exchange membranes (PEMs), but the use of thinner membranes exacerbates hydrogen crossover – which leads to unacceptable levels of hydrogen in the anode effluent poising safety concerns (i.e., above the lower explosion limit of 4 vol% hydrogen in oxygen). Notably, the hydrogen content in the anode effluent is high when operating the PEMWE at low current density values (0.1 to 0.5 A cm-2). A PEMWE will sometimes throttle down and operate at low current density because of the intermittent nature of renewable energy sources which are used to power the electrolyzer. Recombination catalyst (RC) interlayers, located within the PEM, can consume hydrogen and mitigate the hydrogen concentration in the anode effluent. This Talk presents our continuum-level modeling approach for hydrogen crossover in PEMWEs with membranes containing RC interlayers. The model accurately captures the hydrogen content in the anode effluent as a function of the PEMWE current density, cathode back pressure, membrane thickness, anode backpressure, RC location, and RC loading. The modeling results, as well as experimental observations in the literature, suggest that RC interlayer effectiveness is limited by oxygen availability at the RC interlayer. The low oxygen concentration at the interlayer relative to hydrogen arises from the lower solubility of oxygen in hydrated PEMs and the lower diffusivity of oxygen in hydrated PEMs. The Talk concludes with future directions to improve the model as well as suggestions for future experiments to aid the accuracy of the model.

Feasibility of a self‐sustaining microbial fuel cell incorporating natural processes of bacteria and microalgae towards a circular bioeconomy

AbstractA microbial fuel cell (MFC) consisting of a bacterial anode chamber and a microalgal cathode chamber was operated under various conditions to assess its technical feasibility. Maximum achievable power density reached up to 7.13 mW m–2. The traditional MFC process of conversion of carbon sources to bioelectricity in the anodic chamber was compared with a system circulating anodic effluent to the cathode chamber. The bacteria and microalgae simultaneously carried out the carbon recycling and recovery of energy and resources synergizing the performance of MFC. Results indicated a comparable chemical oxygen demand removal efficiencies at 50% of the retention time compared to the traditional system. The dissolved oxygen concentration varied between 11.95 and 7.44 mg L–1 with Chlorella vulgaris under alternative light and dark cycles. Despite the variations in electricity output, the system showed its technical feasibility to harness energy for photosynthesis under natural sunlight conditions.

Mechanistic Insight from Acetate Oxidation in Three-Electrode Cells and Flow Cells

Recent years has seen a tremendous growth in finding electrochemical pathways to produce chemicals and fuels because it is believed that pairing low-carbon electricity (solar, wind, nuclear) with renewable carbon sources and electrochemical processes will lead to a reduction in greenhouse gas emissions. One of the possible sources renewable carbon is biomass. During biomass upgrading, one of the byproducts is bio-oil, which contains a large amount of acetic acid. Acetic acid itself is a relatively low value product. Upgrading acetic acid (or its alkaline counterpart acetate) to a wider range of valuable products (e.g., methanol, ethylene) is extremely attractive. This can be done through thermochemical or electrochemical partial oxidation.Though acetic acid reactions have been studied for many years, details about its overall reaction mechanism still remain unknown. The most known and defended pathway in the literature is Kolbe electrolysis, where C-C bonds are formed from dimerization of methyl radicals as shown in Equation 1.2CH3COOH → 2CO2 + C2H6 + 2H+ + 2e- (Equation 1)However, aqueous environments have shown deviations from this dimerization. It is often overlooked that these reactions occur at high potentials and the state and role of the formed surface oxide are not well described in the literature. It is even not known what water-oxide mechanism dominates for the formation of alcohol-based products. Although prior work has shown that a three-electrode batch cell can produce the typical Kolbe products (ethane and carbon dioxide) at high faradaic efficiencies and steady state when the electrolyte bath is held at the pKa (4.7) and high voltage (>3.0V vs. RHE) – our previous studies have shown that the reaction environment (e.g. concentration, addition of supporting electrolyte, pH) can vary the effluent composition and reaction rate considerably. Also, our recent work has shown that transitioning the same catalyst to a lower-water environment in a flow cell can yield a completely different product profile than in aqueous media.Therefore, the purpose of this study is to demonstrate how the catalyst and reacting environment affect the formation of various C1 and C2 products from acetate electrochemical oxidation. To do this, custom-made two-electrode (similar to an alkaline exchange membrane electrolyzer) and three-electrode cells are used. Another variable that is manipulated is the voltage profile, where both constant voltage and pulsed experiments are performed. In the flow cell, several anode electrocatalysts (e.g., Pt, PtRu, NiO, IrOx) were dispersed in inks and sprayed onto porous transport layers. The anode feed was 0.5M potassium acetate. No gases were fed to the cathode, but hydrogen was collected from the exhaust. The anode effluent (gas and liquid mixture) was separated downstream in a simple vessel with UHP helium flowing through the incoming effluent to carry the gas for GC/MS analysis. Liquid samples were analyzed by ex situ and NMR with D2O solvent. Two-electrode and three-electrode results will be combined to provide new insights into acetate oxidation and pathways for future research and development will be discussed.

Azo dye containing wastewater treatment in earthen membrane based unplanted two chambered constructed wetlands-microbial fuel cells: A new design for enhanced performance

This investigation is the first of its kind to enhance detoxification of azo dye and other pollutants containing wastewater using an innovative earthen membrane-based two-chambered constructed wetland cum microbial fuel cell (CW-MFC). The present innovative design simulates the core of a shallow unplanted CW-MFC, which runs the sequential anaerobic and aerobic regimes without mixing of the cathodic and anodic wastewater. The obtained results revealed 94.04 ± 2.87% chemical oxygen demand (COD) and 94.22 ± 1.33% azo dye removal from the synthetic wastewater containing 550 mg/L initial COD and 50 mg/L Methyl orange (MO) azo dye, along with the current density and power density production of 544.6 mA/m3 and 148.29 mW/m3, respectively. The UV-visible spectrum demonstrated azo bond degradation in the anodic region, which was confirmed by the presence of sulphanilic acid as an intermediate of the azo dye degradation in the anodic effluent. The gas chromatography-mass spectrometry (GC-MS) analysis of anodic effluent proved the presence of an another intermediate, N.N-dimethyl-p-phenylenediamine (DMPD) and further confirms mineralization in the cathodic effluent with the elution of several mineralized polar compounds. Phytotoxicity study with Vigna radiata, Triticum aestivum, and Cicer arietinum indicated higher root growth rates (in comparison to control) of 30.72%, 13.53%, and 11.62% in the anodic effluent, whereas 69.70%, 60.28%, and 34.27% in the cathodic effluent, respectively, indicating decreased toxicity. The microbial analysis revealed a shift in microbial community of CW-MFC; the inoculum was abundant with Methanomicrobia class (18.55%), which shifted to class Bacteroidetes (13.99%) in the anodic region which was attributed to azo dye degrading bacteria. Whereas, cathodic microbial community consists of Alpha and Gamma Proteobacteria (59.50%), which are considered as the aromatic ring-degrading microbes.

Syngas production through CH4-assisted co-electrolysis of H2O and CO2 in La0.8Sr0.2Cr0.5Fe0.5O3-δ-Zr0.84Y0.16O2-δ electrode-supported solid oxide electrolysis cells

High temperature co-electrolysis of H2O/CO2 allows for clean production of syngas using renewable energy, and the novel fuel-assisted electrolysis can effectively reduce consumption of electricity. Here, we report on symmetric cells YSZ-LSCrF | YSZ | YSZ-LSCrF, impregnated with Ni-SDC catalysts, for CH4-assisted co-electrolysis of H2O/CO2. The required voltages to achieve an electrolysis current density of −400 mA·cm−2 at 850 °C are 1.0 V for the conventional co-electrolysis and 0.3 V for the CH4-assisted co-electrolysis, indicative of a 70% reduction in the electricity consumption. For an inlet of H2O/CO2 (50/50 vol), syngas with a H2:CO ratio of ≈2 can be always produced from the cathode under different current densities. In contrast, the anode effluent strongly depends upon the electrolysis current density and the operating temperature, with syngas favorably produced under moderate current densities at higher temperatures. It is demonstrated that syngas with a H2:CO ratio of ≈2 can be produced from the anode at a formation rate of 6.5·mL min−1·cm−2 when operated at 850 °C with an electrolysis current density of −450 mA·cm−2.

Circulation of anodic effluent to the cathode chamber for subsequent treatment of wastewater in photosynthetic microbial fuel cell with generation of bioelectricity and algal biomass

Synthetic wastewater containing 1500 mg L−1 of COD was treated in the anode chamber for 5, 10, and 20 d. An anode chamber was conducted under anaerobic conditions with mixed culture bacteria inoculum attached to the anode. Anodic effluent was transferred to the cathode chamber for further treatment for 5, 10, and 20 d as the growth medium of Chlorella vulgaris. The microalgal photosynthesis process provided oxygen for the cathodic reaction. In 5 d of anodic hydraulic retention time (HRT), the effluent contained high COD, resulting in low power generation in the P-MFC due to the heterotrophic metabolism carried out by microalgae diminishing photosynthesis. However, high biomass productivity up to 0.649 g L−1 d−1 was obtained in the subsequent treatment of 5 d in the cathode chamber. An anodic HRT of 10 d resulted in higher power generation (0.0254 kWh kg−1 COD), and higher COD removal efficiency up to 60%. A further 10 d treatment in the cathode chamber increased the COD removal efficiency up to 74%. Anode and cathode chambers combined removed 79% of NH4+–N concentration from the original synthetic wastewater within 20 d. This study demonstrated that the anodic effluent of the P-MFC can be utilized in the cathode chamber as a growth medium for microalgae if conducted with appropriate HRT in the anode. P-MFC provides a promising sustainable solution for wastewater treatment while generating electricity and algal biomass as by-products.

Excessive extracellular polymeric substances induced by organic shocks accelerate electron transfer of oxygen reducing biocathode

Electrotrophic bacteria on cathodes are promising substitutes to precious metals as oxygen reduction reaction catalysts in bioelectrochemical systems (BESs). Leading the anodic effluent to the biocathode has additional benefits of neutralizing pH and removing residual pollutants. However, the overflow of excessive organic pollutants inhibits the activity of autotrophic biocathodes. Adding glucose as an organic shock, we confirm that the startup time of biocathodes is initially prolonged by 1.2 times with a decrease in current. However, the currents inversely surpass the control in glucose-added BESs when the biofilm is mature, and the maximum current density increase by 5.5 times with a relatively stable performance. This increase is mainly attributed to the production of agglomerates dominated by polysaccharides and proteins as extracellular polymeric substances. These agglomerates wrap additional redox shuttles that accelerated the electron transfer between electrotrophic bacteria and the cathode. This study demonstrates for the first time that organic shocks enhance the electroactivity of autotrophic biocathodes and provides insights into the feedback mechanisms of electrotrophic microbial community to environmental changes.

Simultaneous treatment of lipid rich ghee industry wastewater and power production in algal biocathode based microbial fuel cell

ABSTRACT Microbial fuel cells have been constantly explored as robust technology for complex industrial wastewater treatment. The partial treatment of wastewater in anode chamber of MFC discourages its ability to thrive as stand-alone treatment process and further necessitates secondary treatment, prior to disposal. In our study, we have evaluated sequential treatment of ghee industry wastewater in the anode (primary) and later in microalgae-based biocathode chamber (secondary) to improve the treatment efficiency of bioelectrochemical system. The wastewater collected from ghee manufacturing unit was biochemically treated in the anode chamber after primary sedimentation and at the end of each batch, the anode effluent was transferred to a transient beaker and was used as a source for microalgal growth in cathode chamber without any modification. On comparison with conventional anaerobic treatment, microbial fuel cell could render higher COD removal with lower batch time. The highest power density and current density of 13.7 mW m−2 and 53.5 mA m−2 was produced with abiotic cathode. Though the power production was low in photo-bioelectrochemical system (3.33 mW m−2, 13.45 mA m−2) compared to abiotic cathode the treatment efficiency improved to 96%. Further, the photo-bioelectrochemical reactors enabled eco-friendly and efficient wastewater treatment with considerable power production.

Application of swirling bed electrochemical process in industrial wastewater treatment

Based on the self-made electrochemical device, by measuring the hardness removal rate, bicarbonate removal rate, energy consumption, pH value, etc., during the device operation, the effect of three electrochemical devices on the treatment of actual industrial wastewater, including no filling, filling swirl sheet, filling swirl sheet and mixed resin, was systematically studied. The results show that the removal efficiency of hardness and bicarbonate of industrial wastewater is the best when the swirl metal sheet was added into the electrochemical device. After 5 h, the removal rate of hardness and bicarbonate of cathode and anode was 38.6 and 21.8%, respectively, and the removal rate of bicarbonate of cathode and anode was 62.4 and 100%, respectively. The maximum difference of pH value of anode and cathode effluent just demonstrated that the electrolysis effect was the best. The structure of this device was very conducive to the application in industrial wastewater. In addition, the influence of operational voltage on the electrochemical device filled with swirl sheet was appropriately discussed from the perspective of hardness, current and electric power of the effluent. The analysis results show that 10 V was the best operational voltage. At this time, the current density was 8.11 A/m2, and the hardness removal rate was 89.4%. This study could expand the practical application of electrochemical technology in industrial wastewater treatment and adds some meaningful basic theoretical data.

Concomitant production of bioelectricity and hydrogen peroxide leading to the holistic treatment of wastewater in microbial fuel cell

Microbial fuel cell (MFC) can commendably treat wastewater in anodic chamber with the concurrent production of bioelectricity. If the anodic effluent can be further treated in cathodic chamber through the H2O2 produced in this chamber, it can provide holistic treatment to the wastewater. In this regard, the present investigation focused on the application of Ni and Ni-Pd as cathode catalysts in MFC, which resulted in 2.2 and 2.6 times higher production of H2O2 leading to 15% and 29% higher chemical oxygen demand removal, respectively. Thus, MFCs can be effectively applied as a performant technology for providing comprehensive treatment to wastewater.

Improvement of bioelectricity generation and microalgal productivity with concomitant wastewater treatment in flat-plate microbial carbon capture cell

The unprecedented increase in global population has triggered the energy crisis, climate change and waste disposal issues which are necessitated the advancements in waste to energy technologies. The present study is directed towards evaluating the potential of microbial carbon capture cells (MCC) for simultaneous power generation, wastewater treatment and microalgal biomass production. Chlorella sorokiniana was used to establish the biocathode using anodic effluent as feed. The developed MCC was affected by physico-chemical parameters such as inlet pH, light intensity and photoperiod. The inoculum age of 12 h, inoculum size of 20%v/v, inlet pH 7.5, light intensity of 140 µmol m−2 s−1 and photoperiod of 12:12 (Light:dark) were asserted as most suitable conditions for achieving high performance of biocathode. The electricity generation was dependent upon the O2 availability at cathode and a drastic drop in voltage was observed under O2 limited conditions. Supplementation of anodic off-gas alone to cathode was not sufficient to sustain the growth of microalgae. However, combining internal anodic CO2 channelling with external CO2 pumping at cathode enhanced the performance of MCC. The experimental results revealed maximum open circuit voltage of 637 mV with a maximum power density of 2.32 W m−3. The maximum microalgal dry cell mass of 812 mg L−1 was achieved with an overall COD removal efficiency and energy recovery of 92–95% and 59%, respectively. These sustainability studies show that such a strategy can be applied for real time industrial flue gas treatment along with wastewater treatment in the future.

Microbial electrolysis followed by chemical precipitation for effective nutrients recovery from digested sludge centrate in WWTPs

A two-step sidestream process was investigated for nitrogen (N) and phosphorus (P) recovery from digested sludge centrate. In the first step, a dual-chamber microbial electrolysis cell (MEC) was used for N recovery on the cathode. In the second step, P was recovered as solid precipitates by the addition of Ca2+ or Mg2+ salts in the anodic effluent. The operation of MEC with centrate indicate that N transport from the anode to the cathode chamber is primarily driven by anodic electron transport rather than diffusional transport. Low concentration of readily biodegradable organics in centrate significantly hindered current density (<0.15 A/m2) and led to trivial N recovery on the cathode chamber. The addition of primary sludge fermentation liquor (25 vol%) with centrate as an exogenous source of readily biodegradable organics substantially increased current density up to 6.4 A/m2, along with high TAN removal efficiency of 53 ± 5%. The energy requirement was calculated at 5.8 ± 0.1 kWh/kg-TAN; however, the recovered H2 gas from the cathode was adequate to offset this energy input completely. The addition of Ca2+ salt at a Ca:P molar ratio of 3:1 was optimum for P recovery from the anodic effluent; Mg:P molar ratio of 2:1 was found to be optimum for Mg2+ salt addition. However, optimum doses of both salts resulted in maximum P recovery efficiency of ∼85%, while Mg2+ addition provided an additional 38% TAN removal. These results demonstrate that microbial electrolysis followed by chemical precipitation can promote sustainable nutrients recovery from centrate at municipal wastewater treatment plants where sludge fermentation has already been adopted to provide readily biodegradable carbon source in the biological nutrient removal process.

Feasibility study on a double chamber microbial fuel cell for nutrient recovery from municipal wastewater

Microbial fuel cell (MFC) is currently considered a promising technology for wastewater treatment. This study aims to evaluate the feasibility of a double-chamber MFC in terms of: (i) operating mode (batch mode, self-circulation mode, single-continuous mode) of anolyte on the nutrient accumulation in the catholyte, (ii) aeration conditions (anode effluent with aeration supplied in catholyte; anode effluent without aeration supplied in catholyte; cathode effluent with aeration supplied in catholyte and cathode effluent without aeration supplied in catholyte) on the nutrient recovery and (iii) types of separators (cation exchange membrane (CEM), forward osmosis (FO), and nonwoven (NW)) to remove nutrients toward their recovery from municipal wastewater. Results showed that there was no negligible increase in the phosphate concentration of the catholyte at the three different modes but accumulation of ammonium. At different aeration conditions, nutrients can be recovered by chemical precipitation at high pH generated by the MFC itself. Basically, phosphate was removed by microbial absorption and recovered by chemical precipitation while ammonium was accumulated by current generation and recovered as precipitates. It was found that double-chamber MFC with the CEM as the separator reported the best nutrients removal with >97.58% of NH4+-N and >94.9% of PO43−-P removed/recovered, followed by the MFC with the nonwoven and FO membrane, respectively. Thus, the double-chamber MFC is feasible for recovering nutrients in a comprehensive bioelectrochemical system.

Sanitation of blackwater via sequential wetland and electrochemical treatment

The discharge of untreated septage is a major health hazard in countries that lack sewer systems and centralized sewage treatment. Small-scale, point-source treatment units are needed for water treatment and disinfection due to the distributed nature of this discharge, i.e., from single households or community toilets. In this study, a high-rate-wetland coupled with an electrochemical system was developed and demonstrated to treat septage at full scale. The full-scale wetland on average removed 79 ± 2% chemical oxygen demand (COD), 30 ± 5% total Kjeldahl nitrogen (TKN), 58 ± 4% total ammoniacal nitrogen (TAN), and 78 ± 4% ortho-phosphate. Pathogens such as coliforms were not fully removed after passage through the wetland. Therefore, the wetland effluent was subsequently treated with an electrochemical cell with a cation exchange membrane where the effluent first passed through the anodic chamber. This lead to in situ chlorine or other oxidant production under acidifying conditions. Upon a residence time of at least 6 h of this anodic effluent in a buffer tank, the fluid was sent through the cathodic chamber where pH neutralization occurred. Overall, the combined system removed 89 ± 1% COD, 36 ± 5% TKN, 70 ± 2% TAN, and 87 ± 2% ortho-phosphate. An average 5-log unit reduction in coliform was observed. The energy input for the integrated system was on average 16 ± 3 kWh/m3, and 11 kWh/m3 under optimal conditions. Further research is required to optimize the system in terms of stability and energy consumption.

Electricity and biomass production in a bacteria- Chlorella based microbial fuel cell treating wastewater

Abstract The chlorophyte microalga Chlorella vulgaris has been exploited within bioindustrial settings to treat wastewater and produce oxygen at the cathode of microbial fuel cells (MFCs), thereby accumulating algal biomass and producing electricity. We aimed to couple these capacities by growing C. vulgaris at the cathode of MFCs in wastewater previously treated by anodic bacteria. The bioelectrochemical performance of the MFCs was investigated with different catholytes including phosphate buffer and anode effluent, either in the presence or absence of C. vulgaris . The power output fluctuated diurnally in the presence of the alga. The maximum power when C. vulgaris was present reached 34.2 ± 10.0 mW m −2 , double that observed without the alga (15.6 ± 9.7 mW m −2 ), with a relaxation of 0.19 gL −1 d −1 chemical oxygen demand and 5 mg L −1 d −1 ammonium also removed. The microbial community associated with the algal biofilm included nitrogen-fixing ( Rhizobiaceae ), denitrifying ( Pseudomonas stutzeri and Thauera sp., from Pseudomonadales and Rhodocyclales orders, respectively), and nitrate-reducing bacteria ( Rheinheimera sp. from the Alteromonadales ), all of which likely contributed to nitrogen cycling processes at the cathode. This paper highlights the importance of coupling microbial community screening to electrochemical and chemical analyses to better understand the processes involved in photo-cathode MFCs.

Bioelectrochemical approach for reductive and oxidative dechlorination of chlorinated aliphatic hydrocarbons (CAHs)

A sequential reductive-oxidative treatment was developed in this study in a continuous-flow bioelectrochemical reactor to address bioremediation of groundwater contaminated by trichloroethene (TCE) and less-chlorinated but still harmful intermediates, such as vinyl chloride. In order to optimize the anodic compartment, whereby the oxygen-driven microbial oxidation of TCE-daughter products occurs, abiotic batch experiments were performed with various anode materials poised at +1.20 V vs. SHE (i.e., graphite rods and titanium mesh anode coated with mixed metal oxides (MMO)) and setups (i.e., electrodes embedded within a bed of silica beads or graphite granule). The MMO anode displayed higher efficiency (>90%) for oxygen generation compared to the graphite electrodes. Additionally, the graphite bed presence adversely affects oxygen generation, likely due to the oxygen scavenging. This effect was completely eliminated by replacing the graphite granules with silica beads. The anodic setups were thereafter verified in a mentioned reactor at an applied TCE loading rate of approximately 20 μM d−1 and a hydraulic retention time of 1.4 d in each compartment. The cathode consisted of a bed of graphite granules and was potentiostatically controlled at −0.65 V vs. SHE. The best reactor performance in terms of removal efficiency (i.e., >97%), removal rate (i.e., 121.8 ± 2.7 μeq L−1 d−1), and the residual concentration (i.e., 5.03 ± 0.63 μeq L−1) of chlorinated contaminants was achieved with the MMO anode placed in a silica bed. Ecotoxicity tests performed with algae confirmed these results by showing progressive toxicity reduction from inlet to cathodic and anodic effluent using this reactor configuration.

Self-Driven Desalination and Advanced Treatment of Wastewater in a Modularized Filtration Air Cathode Microbial Desalination Cell.

Microbial desalination cells (MDCs) extract organic energy from wastewater for in situ desalination of saline water. However, to desalinate salt water, traditional MDCs often require an anolyte (wastewater) and a catholyte (other synthetic water) to produce electricity. Correspondingly, the traditional MDCs also produced anode effluent and cathode effluent, and may produce a concentrate solution, resulting in a low production of diluate. In this study, nitrogen-doped carbon nanotube membranes and Pt carbon cloths were utilized as filtration material and cathode to fabricate a modularized filtration air cathode MDC (F-MDC). With real wastewater flowing from anode to cathode, and finally to the middle membrane stack, the diluate volume production reached 82.4%, with the removal efficiency of salinity and chemical oxygen demand (COD) reached 93.6% and 97.3% respectively. The final diluate conductivity was 68 ± 12 μS/cm, and the turbidity was 0.41 NTU, which were sufficient for boiler supplementary or industrial cooling. The concentrate production was only 17.6%, and almost all the phosphorus and salt, and most of the nitrogen were recovered, potentially allowing the recovery of nutrients and other chemicals. These results show the potential utility of the modularized F-MDC in the application of municipal wastewater advanced treatment and self-driven desalination.

Recovery of nitrogen and water from landfill leachate by a microbial electrolysis cell–forward osmosis system

A microbial electrolysis cell (MEC)–forward osmosis (FO) system was previously reported for recovering ammonium and water from synthetic solutions, and here it has been advanced with treating landfill leachate. In the MEC, 65.7±9.1% of ammonium could be recovered in the presence of cathode aeration. Without aeration, the MEC could remove 54.1±10.9% of ammonium from the leachate, but little ammonia was recovered. With 2M NH4HCO3 as the draw solution, the FO process achieved 51% water recovery from the MEC anode effluent in 3.5-h operation, higher than that from the raw leachate. The recovered ammonia was used as a draw solute in the FO for successful water recovery from the treated leachate. Despite the challenges with treating returning solution from the FO, this MEC–FO system has demonstrated the potential for resource recovery from wastes, and provide a new solution for sustainable leachate management.

Self-Supplied Ammonium Bicarbonate Draw Solute for Achieving Wastewater Treatment and Recovery in a Microbial Electrolysis Cell-Forward Osmosis-Coupled System

This study has presented a proof-of-concept system for the self-sustained supply of ammonium-based draw solute for wastewater treatment through coupling a microbial electrolysis cell (MEC) and forward osmosis (FO). The MEC produced an ammonium bicarbonate draw solute via recovering ammonia from a synthetic organic solution, which was then applied in the FO for extracting water from the MEC anode effluent. The recovered ammonium could reach a concentration of 0.86 mol L–1, and with this draw solution, the FO extracted 50.1 ± 1.7% of the MEC anode effluent. The lost ammonium during heat regeneration could be supplemented with additional recovered ammonium in the MEC. The MEC achieved continuing treatment of both organic and ammonium in the returned feed solution mixed with fresh anolyte, although at lower efficiency compared to that with completely fresh anolyte. These results encourage further investigation to optimize the coordination between MEC and FO with improved performance.