Simultaneous removal of sediment and water contaminants in a microbial electrochemical system with embedded active electrode by in-situ utilization of electrons.

In the water environment such as lakes, there is a phenomenon that the sediment and overlying water are polluted at the same time. In this study, A microbial electrochemical system with an embedded active electrode was developed for simultaneous removal of polycyclic aromatic hydrocarbons in sediment and antibiotics in overlying water by in-situ utilization of electrons. In the closed-circuit group, the pyrene concentration in sediment decreased from 9.94 to 2.08 mg/L in 96 d, and the sulfamethoxazole concentration in water decreased from 5.12 to 1.12 mg/L in 168 h. These values were 18.71 % and 31.21 % higher, respectively, than those of the open-circuit group. The pyrene degradation pathway may be from polycyclic aromatic substances to low-cyclic aromatic hydrocarbons via successive breakdown of benzene rings. Multiple metabolites produced by reduction verified that SMX or its intermediates were reductively degraded in water. On the active electrode, the relative abundances of Acetobacterium and Piscinibacter, which were genera related to SMX degradation, was promoted, while the electricity-producing genus Pseudomonas was inhibited. ccdA, pksS, torC, and acsE genes related to extracellular electron transport may accelerate electron transport. Electrons could be transferred to SMX under the influence of proteins involved in extracellular electron transport, and SMX could be degraded reductively as an electron acceptor by microbes. Generation of electrons and in-situ utilization for simultaneous removal of solid-liquid two-phase pollutants will provide mechanistic insight into pollutant biodegradation by microbial electrochemistry and promote the development of sustainable bioremediation strategies for surface water.

Enhanced degradation of bisphenol A and ibuprofen by an up-flow microbial fuel cell-coupled constructed wetland and analysis of bacterial community structure.

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.

Enhanced degradation of azo dye by a stacked microbial fuel cell-biofilm electrode reactor coupled system.

In this study, a microbial fuel cell (MFC)-biofilm electrode reactor (BER) coupled system was established for degradation of the azo dye Reactive Brilliant Red X-3B. In this system, electrical energy generated by the MFC degrades the azo dye in the BER without the need for an external power supply, and the effluent from the BER was used as the inflow for the MFC, with further degradation. The results indicated that the X-3B removal efficiency was 29.87% higher using this coupled system than in a control group. Moreover, a method was developed to prevent voltage reversal in stacked MFCs. Current was the key factor influencing removal efficiency in the BER. The X-3B degradation pathway and the types and transfer processes of intermediate products were further explored in our system coupled with gas chromatography-mass spectrometry.

[Effects of Microbial Fuel Cell Coupled Constructed Wetland with Different Support Matrix and Cathode Areas on the Degradation of Azo Dye and Electricity Production].

In this study, microbial fuel cell coupled constructed wetland (CW-MFC) was constructed for azo dye reactive brilliant red X-3B degradation and electricity production. The effects of support matrix and cathode areas on the degradation of X-3B and the electricity production of CW-MFC were investigated in this work to improve the performance of CW-MFC. The highest decolorization efficiency was 92.70% and was obtained when the CW-MFC was constructed with support matrix S3 with particle size of 10 mm and porosity of 30%. Small particle size increased the microbial biomass of the bottom layer of CW-MFC, which would promote the decolorization of X-3B in the bottom layer. However, it may cause the lack of nutrition in electrode layer and the increase in resistance of mass transfer, which would lead to the decline of electricity production. The decolorization efficiency and the power density of CW-MFC increased concomitantly with the increase of cathode areas, and the CW-MFC got the highest decolorization efficiency of 99.41% when the cathode area was 594 cm2. The electricity production performance became stable when the cathode area continued to increase, while the decolorization efficiency declined. This may be attributed to that more electrons were transferred to the cathode to produce current instead of used in degradation of X-3B.

Simultaneous degradation of toxic refractory organic pesticide and bioelectricity generation using a soil microbial fuel cell.

In this study, the soil microbial fuel cells (MFCs) were constructed in the topsoil contaminated with toxic refractory organic pesticide, hexachlorobenzene (HCB). The performance of electricity generation and HCB degradation in the soil-MFCs were investigated. The HCB degradation pathway was analyzed based on the determination of degradation products and intermediates. Experimental results showed that the HCB removal efficiencies in the three groups (soil MFCs group, open circuit control group and no adding anaerobic sludge blank group) were 71.15%, 52.49% and 38.92%, respectively. The highest detected power density was 77.5 mW/m(2) at the external resistance of 1000 Ω. HCB was degraded via the reductive dechlorination pathway in the soil MFC under anaerobic condition. The existence of the anode promoted electrogenic bacteria to provide more electrons to increase the metabolic reactions rates of anaerobic bacteria was the main way which could promote the removal efficiencies of HCB in soil MFC.

Electricity production from Azo dye wastewater using a microbial fuel cell coupled constructed wetland operating under different operating conditions.

Microbial fuel cells (MFCs) have got tremendous attention for their capability to enhance the degradation of some recalcitrant pollutants and simultaneous electricity production. A microbial fuel cell coupled constructed wetland (CW-MFC) is a new device to treat the wastewater and produce energy which has more wastewater treatment volume and more easily to maintenance than others MFCs. The studies on the performance of CW-MFCs are necessary. In this work, the effects of hydraulic residence time (HRT), reactive brilliant red X-3B (ABRX3) proportion and COD concentration on the electricity production of CW-MFC and the degradation characteristics of ABRX3 were investigated. The decolorization rate and the electricity production increased to a peak before slowing down with the elongation of HRT. The highest decolorization rate and electricity production were obtained when HRT was 3 days. The ABRX3 proportion (calculated as COD) in the wastewater played an important role in decolorization and electricity production, which may influence the distribution of electrons in the system. The power density of CW-MFC and the decolorization rate decreased concomitantly with an increasing ABRX3 proportion. The COD concentration influenced the CW-MFC performance slightly. The highest decolorization rate and power density reached 95.6% and 0.852 W/m(3), respectively, when the COD concentration was 300 mg/L while the ABRX3 proportion was 30%. The coulombic efficiency of the CW-MFC depended on glucose and ABRX3 proportions in the wastewater. ABRX3 acquired more electrons than the anode. Further investigations are needed to optimize CW-MFC performance and explain the mechanism of biorefractory compounds degradation and electron motion in CW-MFCs.

Performance of microbial fuel cell coupled constructed wetland system for decolorization of azo dye and bioelectricity generation.

A microbial fuel cell coupled constructed wetland (planted with Ipomoea aquatica) system (planted CW-MFC) was used for azo dye decolorization. Electricity was simultaneously produced during the co-metabolism process of glucose and azo dye. A non-planted and an open-circuit system were established as reference to study the roles of plants and electrodes in azo dye decolorization and electricity production processes, respectively. The results indicated that plants grown in cathode enhanced the cathode potential and slightly promoted dye decolorization efficiency. The electrodes promoted the dye decolorization efficiency in the anode. The planted CW-MFC system achieved the highest decolorization rate of about 91.24% and a voltage output of about 610 mV. The connection of external circuit promoted the growth of electrogenic bacteria Geobacter sulfurreducens and Beta Proteobacteria, and inhibited the growth of Archaea in anode.

[Removal pathway and influence factors of hydroponic bio-filter method for nitrogen and phosphorus].

Study was made on the use of hydroponic bio-filter method (HBFM) for eutrophic surface water. Results show that HBFM can remove 16.8% of TN and 30.8% of TP at the hydraulic loading rate (HLR) of 3.0 m3/(m2 x d). The removal loading rate of TN and TP can accordingly reach 1.0 and 0.1 g/(m2 x d) respectively. The sedimentation of particulate nitrogen and particulate phosphorus plays a major role in nitrogen and phosphorus removal, and its contribution is 62.2% and 75.9% respectively. The optimal HLR of HBFM ranges from 3.0 to 4.0 m3/(m x d). The intension of secateur for Nasturtium officinale has some effect on its uptake rate, thus the length of cut when harvesting should be less than 10 cm. The harvesting frequency of once a month for Nasturtium officinale has no effect on nitrogen and phosphorus removal of HBFM.

[Characteristic of combined floating bed ecosystem for water purification under dynamic condition].

A new type of ecological floating bed was developed that combined hydrophyte, aquatic animal and biofilm. The dynamic pilot study on purification characteristic and mechanism of the floating bed for eutrophic was carried out. Result shows that the removal efficiencies of TN, TP and COD(Mn), are 53.8%, 86.0% and 35.4% respectively under the water exchange period of 7 days. Main purification role is played by artificial medium and aquatic macrophyte in pollutants removal, but the Corbicula fluminea introduced to food chain of combined floating bed enhances the purification effect through the ways as follows: improving the resolvability, ammonification and biodegradability of particulate organic matters, meliorating the substrate supply condition for absorption of plant and degradation of microorganism attached on artificial medium, hastening the growth and activity of microorganism.