Co-reporter:Shiting Ren;Mengchen Li;Jianyu Sun
Frontiers of Environmental Science & Engineering 2017 Volume 11( Issue 4) pp:17
Publication Date(Web):05 August 2017
DOI:10.1007/s11783-017-0983-x
To separate and concentrate NH4+ and PO43– from the synthetic wastewater to the concentrated solution through a novel electrochemical reactor with circulated anode and cathode using the difference of the concentration between electrode chamber and middle chamber.In recent years, the research on electrochemical processes have been focused on phosphate and ammonium removal and recovery. Among the wide range of possibilities with regards to electrochemical processes, capacitive deionization (CDI) saves the most energy while at the same time does not have continuity and selectivity. In this study, a new electrochemical reactor with electrolyte cyclic flowing in the electrode chambers was constructed to separate and concentrate phosphate and ammonium continuously and selectively from wastewater, based on the principle of CDI. At the concentration ratio of NaCl solution between the electrode chambers and the middle chamber (r) of 25 to 1, phosphate and ammonium in concentration level of domestic wastewater can be removed and recovered continuously and selectively as struvite. Long-term operation also indicated the ability to continuously repeat the reaction and verified sustained stability. Further, the selective recovery at the certain r could also be available to similar technologies for recovering other kinds of substances.
Co-reporter:Jiao Zhang;Zhen Wei;Haifeng Jia
Frontiers of Environmental Science & Engineering 2017 Volume 11( Issue 4) pp:8
Publication Date(Web):13 May 2017
DOI:10.1007/s11783-017-0943-5
The water quality in a typical urban river segment originated with reclaimed water in Beijing was monitored for two years to investigate the evolution of water quality along the river, and statistical analysis was applied to determine factors influencing water quality of such river recharged by reclaimed water. It was found that no significant change in pollutant concentrations (including COD, NH4+-N, TN and TP) was observed during this time, and their average values were close to those of the original reclaimed water. However, turbidity and algal contents fluctuated temporally in the direction of river flow. Statistical analysis showed that turbidity was strongly positively correlated with algal contents for flow rate <0.1 m•s–1, whereas it was strongly positively correlated with both algal contents and TOC for flow rate > 0.1 m•s–1. It was observed that diatom was the absolute predominant phyla with Melosira as the major species. In terms of algal bloom control, the specific growth rate of algae was strongly correlated to temperature, and was influenced by flow rate as well. Compared with two other rivers originated with reclaimed water and one originated with natural water, the Shannon–Wiener index in the objective river was the lowest, with values between 0.7 and 1.6, indicating a high risk for algal bloom. Statistics showed that Shannon–Wiener index was strongly negatively correlated to nutrient salts and cations.
Co-reporter:Ying Xu, Ningwei Zhu, Jianyu Sun, Peng Liang, Kang Xiao, Xia Huang
Process Biochemistry 2017 Volume 60(Volume 60) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.procbio.2017.05.020
•Aeration intensity, bubble size and diffuser submerged depth affect kLa.•MLSS, EPS and apparent viscosity correlate significantly with α-factor.•Quantitative expressions are proposed to evaluate α-factor for large-scale MBRs.For lack of relevant investigation in the context of large-scale membrane bioreactors (MBRs), evaluation of the oxygen mass transfer parameters is important for the optimized design of the aeration system in an MBR process. In this study, we sampled the actual sludge from several large-scale MBRs (>10,000 m3/d) for the oxygen transfer tests. It was found that specific surface area of bubbles, aeration intensity, and diffuser submerged depth had positive effect on the oxygen transfer coefficient (kLa), while some mixed liquor characteristics such as the mixed liquor suspended solids (MLSS) concentration and apparent viscosity exerted negative function on it. We further proposed quantitative expressions to predict the alpha-factor (α-factor) under typical aeration conditions. The α-factor was found to be above 0.6 when MLSS was roughly less than 12 g/L, which was generally higher than the α-factor predicted in the previous literature, such that overestimation of aeration demand in large-scale MBRs might be avoided.Download high-res image (215KB)Download full-size image
Co-reporter:Shuo Zhang, Jiali Chang, Chao Lin, Yiran Pan, Kangping Cui, Xiaoyuan Zhang, Peng Liang, Xia Huang
Bioresource Technology 2017 Volume 245, Part A(Volume 245, Part A) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.biortech.2017.08.111
•Conductive GAC promoting methanogenesis remarkably.•Promoting methanogenesis by GAC was not by increasing biomass.•Promoting methanogenesis with GAC probably was related with DIET.•GAC may play the role of c-Cyts’ substitution in DIET.To understand how granular activated carbon (GAC) promotes methanogenesis, batch tests of CH4 production potential in anaerobic serum bottles with addition of GAC or not were conducted. Tests showed that GAC promoted methanogenesis remarkably, but the non-conductive zeolite did not. The qPCR demonstrated that the biomass on GAC contributed little to the promotion. High-throughput sequencing data implied that promotion was related with direct interspecies electron transfer between Geobacteraceae and Methanosaetaceae. According to the c-type cytochromes (c-Cyts) response to the supplement of GAC, it was speculated that GAC may play the role of c-Cyts’ substitution. In the undefined cultures, the phenomenon that c-Cyts were repressed by GAC was first observed. This research provided new evidence to microbial mechanism of promoting methanogenesis via GAC.Download high-res image (57KB)Download full-size image
Co-reporter:Shijia Wu, Weihua He, Wulin Yang, Yaoli Ye, Xia Huang, Bruce E. Logan
Journal of Power Sources 2017 Volume 356(Volume 356) pp:
Publication Date(Web):15 July 2017
DOI:10.1016/j.jpowsour.2017.01.041
•A novel composite anode was developed that combined brushes and carbon mesh.•The composite anode had higher power output and CEs than either of the other anodes.•Power overshoot was mitigated with the composite anode MFCs at higher CODs.•MFCs with the composite anode had less cathode biomass growth.•The carbon mesh with biofilms in the composite anode also functioned as a separator.Microbial fuel cells (MFCs) need to have a compact architecture, but power generation using low strength domestic wastewater is unstable for closely-spaced electrode designs using thin anodes (flat mesh or small diameter graphite fiber brushes) due to oxygen crossover from the cathode. A composite anode configuration was developed to improve performance, by joining the mesh and brushes together, with the mesh used to block oxygen crossover to the brushes, and the brushes used to stabilize mesh potentials. In small, fed-batch MFCs (28 mL), the composite anode produced 20% higher power densities than MFCs using only brushes, and 150% power densities compared to carbon mesh anodes. In continuous flow tests at short hydraulic retention times (HRTs, 2 or 4 h) using larger MFCs (100 mL), composite anodes had stable performance, while brush anode MFCs exhibited power overshoot in polarization tests. Both configurations exhibited power overshoot at a longer HRT of 8 h due to lower effluent CODs. The use of composite anodes reduced biomass growth on the cathode (1.9 ± 0.2 mg) compared to only brushes (3.1 ± 0.3 mg), and increased coulombic efficiencies, demonstrating that they successfully reduced oxygen contamination of the anode and the bio-fouling of cathode.
Co-reporter:Kuichang Zuo, Jiali Chang, Fubin Liu, Xiaoyuan Zhang, Peng Liang, Xia Huang
Desalination 2017 Volume 423(Volume 423) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.desal.2017.09.018
•A multistage microbial desalination cell was used to treat industrial wastewater.•High strength organics were removed in alternative anaerobic/oxic electrodes.•Nitrogen was removed by coefficient electrical migration and bio-denitrification.•Desalination and organics removal was enhanced by adding 1.0 V external voltage.Conventional microbial desalination cells (MDCs) extract organic energy from wastewater for in situ desalination of saline water, but cannot treat industrial wastewater containing high strength organics that may cause blocking in the thin membrane stack. In this study, a multi-stage MDC (M-MDC) was fabricated and operated for simultaneous treatment and desalination of diluted industrial wastewater. With wastewater (COD: 8723 ± 456 mg/L, conductivity: 24,612 ± 772 μS/cm) flowing serially from anode-1 → cathode-1 → anode-2 → cathode-2, the maximum power density of the M-MDC reached 566.1 mW/m2, with removal efficiencies of COD, TN, NH4+-N, and conductivity reaching 97.8%, 90.6%, 98.4%, and 31.6% respectively with addition of 1 V external voltage. The high strength organics were significantly removed due to alternative anaerobic/oxic conditions, the nitrogen removal was enhanced by simultaneous electrical migration and biological nitrification/denitrification. Moreover, the addition of external voltage enhanced current generation (67.4 ± 3.9 mA), desalination efficiency, coulombic efficiency (14.1%), and organics removal in two anodes (47.3%), producing an effluent (COD < 500 mg/L, TN < 15 mg/L) qualified to be discharged into municipal wastewater pipe systems. These results indicated great potential of M-MDC to work as a pretreatment technology for high strength industrial wastewater.Download high-res image (187KB)Download full-size image
Co-reporter:Yonghua Yao and Xia Huang
Chemical Communications 2016 vol. 52(Issue 16) pp:3324-3327
Publication Date(Web):15 Jan 2016
DOI:10.1039/C5CC09887D
By using an electrochemical strategy, we demonstrated that ferrous ions are capable of decreasing bacterial EET activity in a certain potential range where the conduction-band edge of natural abundant iron(III) oxides is located. It is proposed that ferrous ions enable alteration of the formal potential of outer membrane c-type cytochromes, a crucial protein involved in the EET process.
Co-reporter:Xi Chen, Haotian Sun, Peng Liang, Xiaoyuan Zhang, Xia Huang
Journal of Power Sources 2016 Volume 324() pp:79-85
Publication Date(Web):30 August 2016
DOI:10.1016/j.jpowsour.2016.05.065
•The number of MDC desalination cells was optimized between 6 and 14.•The 10-desalination-cell reactor achieved the highest TDR (423 mg/h) and CTE (836%).•TDR is a factor which decreased with time during the desalination process.•CTE is a factor which was primarily determined by the membrane stack configuration.•Junction potential significantly increased during the desalination process.Microbial desalination cells are considered a low-energy-consumption, clean technology to simultaneously purify wastewater and desalinate saline water by utilizing the in situ energy source contained in wastewater. To enhance desalination performance and achieve an optimal membrane stack configuration, an enlarged stacked microbial desalination cell (SMDC) has been developed and tested with 6–14 desalination cells. The cross-membrane area of the enlarged SMDC is 100 cm2. The anode and cathode volumes are both 200 mL. To reduce internal resistance, the width of desalination cells is kept as <0.5 mm. The optimal configuration with 10 desalination cells achieves the highest total desalination rate (TDR) of 423 mg/h and the highest charge transfer efficiency (CTE) of 836% when treating the 20 g/L NaCl solution. During this process, the junction potential across membranes increases from 0 to 374 mV, and occupies up to 74% of the total potential loss inside the SMDC. This shows that the SMDC used in this work achieves the highest TDR and CTE among the reported studies, and the junction potential should be effectively controlled to achieve the desired desalination performance in future practical applications.
Co-reporter:Kuichang Zuo, Zhen Wang, Xi Chen, Xiaoyuan Zhang, Jiaolan Zuo, Peng Liang, and Xia Huang
Environmental Science & Technology 2016 Volume 50(Issue 13) pp:7254-7262
Publication Date(Web):June 8, 2016
DOI:10.1021/acs.est.6b00520
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.
Co-reporter:Kuichang Zuo, Han Liu, Qiaoying Zhang, Peng Liang, Chad D. Vecitis, Xia Huang
Electrochimica Acta 2016 Volume 211() pp:199-206
Publication Date(Web):1 September 2016
DOI:10.1016/j.electacta.2016.05.104
In this study, nitrogen-doped carbon nanotube (N-CNT) membrane compared with Pt-coated CNT (Pt-CNT) membrane and pristine CNT membrane were utilized as air cathode as well as filtration material of microbial fuel cells (MFCs). The MFCs were continuously operated for 39 days to investigate their power generation, organics removal, proton transfer, and fouling behavior under various influent concentrations and hydraulic retention times (HRTs). During operation, the N-CNT filtration MFC achieved the best effluent quality and power generation, with efficient removal of total organic carbon (TOC) (95.2%) and NH4+-N (97.7%), and maximum power density and current density of 408 mW/m2 and 2.36 A/m2 respectively. The excellent performance of the N-CNT MFC was mainly attributed to its special morphology and rich N-functional groups. The N-CNT membrane has a nanotube diameter of 37 ± 4 nm, pore size of 95 ± 33 nm, and porosity of 79.9%, which was even better than traditional microfiltration membrane as a filtration material for pollutant removal. The high nitrogen content (2.12 at%) and high specific surface area (93.5 m2/g) due to its network structure also enhanced O2 reduction. In addition to the excellent performance of N-CNT cathode, the filtration operation enhanced cathode O2 reduction by increasing mass transfer in cathode micro-pore and improving proton transfer with water flowing from anode to cathode. Moreover, a separate experiment also demonstrated that the cathode fouling could be mitigated under high current operation.
Co-reporter:Kang Xiao, Jian-Yu Sun, Yue-Xiao Shen, Shuai Liang, Peng Liang, Xiao-Mao Wang and Xia Huang
RSC Advances 2016 vol. 6(Issue 29) pp:24050-24059
Publication Date(Web):22 Feb 2016
DOI:10.1039/C5RA23167A
Dissolved organic matter (DOM) plays a substantial role in wastewater treatment systems. Fluorescence is an important property of DOM and its use is promising for DOM characterization, but has rarely been extended to probing the basic physicochemical properties such as hydrophobicity and molecular weight. This study explores the possible linkages between the fluorescence properties and hydrophobicity/molecular weight of DOM, through case studies from three wastewater treatment plants (two membrane bioreactors and one oxidation ditch). The fluorescence properties of different hydrophobic/hydrophilic and molecular-weight fractions of DOM were obtained using excitation–emission matrix (EEM) spectroscopy and size-exclusion chromatography with fluorescence detection. The EEM spectra were interpreted using techniques of fluorescence regional integration, parallel factor analysis, fluorescence spectroscopic indices, and a novel energetic mapping based on fluorophore energy levels. It was found that for all the three plants, the hydrophobic fractions of DOM had a higher fluorescence intensity per UV absorbance (indicating a higher quantum yield) as well as a larger Stokes shifts than the hydrophilic fraction. The lower-molecular-weight fractions generally exhibited a higher fluorescence intensity per total organic carbon (indicating a higher fluorophore density), with the fluorescence distribution at slightly smaller excitation and emission wavelengths. These phenomena were explained via analysis of the fluorophore energy state during the excitation/emission process. The scale of the π-conjugated system in DOM molecules may serve as an intermediate factor in the correlations between the hydrophobicity/molecular weight and the fluorescence properties. These correlations may assist in developing fluorescent probes for the DOM characteristics during the process monitoring of wastewater treatment plants.
Co-reporter:Nuerla Ailijiang;Jiali Chang;Qing Wu;Peng Li;Peng Liang
Water, Air, & Soil Pollution 2016 Volume 227( Issue 7) pp:
Publication Date(Web):2016 July
DOI:10.1007/s11270-016-2924-x
The effect of direct current (DC) on phenol biodegradation under aerobic/anaerobic condition was investigated in this study using a bioelectrochemical reactor. It was found that phenol biodegradation was inhibited with current ranged from 10 to 40 mA. The growth of biomass was reduced to 43.2 ± 6.6 % for aerobic sludge and 38.6 ± 7.3 % for anaerobic sludge, but the loosely bound extracellular polymer substances (LB–EPS) were increased 91.2 ± 1.3 % for aerobic sludge and 62.8 ± 0.8 % for anaerobic sludge as the current increased from 10 to 40 mA. Adenosine triphosphate (ATP) content of aerobic sludge was also reduced 0.481 ± 0.04-fold and 0.512 ± 0.05-fold lower and 1.34 ± 0.13-fold higher than that of the control when the current was increased from 10 to 40 mA. The results of phosphate buffer saline adding treatment indicated that lower pH caused by a DC above 10 mA was responsible for the reduced phenol biodegradation, leading to the reduction of biomass. However, lower intensity of current (5 mA) had no significant impact on phenol degradation rate, pH, LB–EPS, ATP content, and cell growth of aerobic/anaerobic sludge. These results give us a more detailed understanding of the effects of electricity on the treatment of phenol containing wastewater.
Co-reporter:Shijia Wu, Peng Liang, Changyong Zhang, Hui Li, Kuichang Zuo, Xia Huang
Electrochimica Acta 2015 Volume 161() pp:245-251
Publication Date(Web):10 April 2015
DOI:10.1016/j.electacta.2015.02.028
•GAC-MFC delivered much better performance than GG-MFC at low COD concentrations.•Increasing circulation flow rate caused more improvement in GAC-MFC’s performance.•GAC adsorption greatly promoted anode mass transfer at low COD concentrations.•GAC adsorption helped to mitigate the impact of COD concentrations’ perturbation.In this study, a microbial fuel cell (MFC) with granular activated carbon packed anode (GAC-MFC) is developed and compared with a MFC with granular graphite packed anode (GG-MFC), to evaluate the adsorptive effect of the granular activated carbon anode on MFC’s performance. The current output of GAC-MFC (11.1 mA, 18.1 mA and 21.6 mA) is much higher than that of GG-MFC (4.87 mA, 12.5 mA and 17.9 mA) at low substrate COD concentrations (∼50, ∼100 and ∼200 mg/L) when a low external resistance (20 Ω) and high circulation flow rate (20 mL/min) are applied. The half-saturation constant (Ks) of GAC-MFC is about half as much as that of GG-MFC, suggesting that GAC-MFC has more affinity for anode substrate and deliver better kinetic performance than GG-MFC. Internal resistance distribution shows that mass diffusion resistance of GAC-MFC is at least 50% lower than that of GG-MFC when the substrate COD is ∼50 mg/L, indicating that the adsorptive effect of granular activated carbon packed anode helps to effectively facilitate mass transfer at low COD concentrations. Otherwise, the substrates adsorbed on GAC surface also serve to buffer the impact of COD concentration plummeting in bulk solution.
Co-reporter:Kuichang Zuo;Han Liu;Qiaoying Zhang; Peng Liang; Xia Huang; Chad D. Vecitis
ChemSusChem 2015 Volume 8( Issue 12) pp:2035-2040
Publication Date(Web):
DOI:10.1002/cssc.201500258
Abstract
The traditional chamber-based microbial fuel cell (MFC) often has the disadvantages of high ohmic resistance, large volume requirements, and delayed start-up. In this study, paper-shaped MFCs utilizing a porous carbon anode, a solid Ag2O-coated carbon cathode, and a micrometer-thin porous polyvinylidene fluoride (PVDF) separator are investigated to address the classical MFC issues. The Ag2O-coated cathode has a low overpotential of 0.06 V at a reducing current of 1 mA compared to a Pt–air cathode. Rapid inoculation by filtration results in an instantaneous power density of 92 mW m−2 with an internal resistance of 162 Ω. Integrated current over the first 30 min of operation has a linear relation with microbial concentration.
Co-reporter:Peng Li, Nuerla Ailijiang, Xiaoxin Cao, Ting Lei, Peng Liang, Xiaoyuan Zhang, Xia Huang, Jilin Teng
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2015 Volume 482() pp:177-183
Publication Date(Web):5 October 2015
DOI:10.1016/j.colsurfa.2015.05.006
•Three adsorbents were used to pretreat coal gasification wastewater.•Pore size distribution of different adsorbents was investigated.•Activated carbon (coal) had a better COD adsorption performance.•Activated coke had a prior adsorption to aromatic refractory compounds.•Mesopores percentage of activated coke was 63%.Powdered (below 125 μm) activated carbons made by wood (WAC) and coal (CAC) and activated coke (AC), whose BET surface areas were 551, 335 and 484 m2/g, respectively, were studied to adsorb organic pollutants from coal gasification wastewater (CGWW). This study initially focused on the equilibrium sorption isotherms of adsorbents for the removal of chemical oxygen demand (COD) from CGWW. Molecular weight (MW) distribution and fluorescence excitation emission matrix (FEEM) were used to determine the difference of CGWW quality. Water qualities of CGWW before and after adsorption by adsorbents were also investigated. The isotherm results showed that Langmuir model fit the adsorption isotherms of activated carbons, while Freundlich model was better for that of AC. CAC and AC had a higher adsorption capacity under lower and higher COD concentration, respectively. It was also found from MW distribution and FEEM results that AC had a prior adsorption to high MW aromatic, refractory compounds in CGWW, which is good for the following biological treatment and suitable for pretreatment. This was because that the mesopores percentage of AC was 63%, which was higher than WAC and CAC.
Co-reporter:Xi Luo, Fang Zhang, Jia Liu, Xiaoyuan Zhang, Xia Huang, and Bruce E. Logan
Environmental Science & Technology 2014 Volume 48(Issue 15) pp:8911-8918
Publication Date(Web):July 2, 2014
DOI:10.1021/es501979z
The utilization of bioelectrochemical systems for methane production has attracted increasing attention, but producing methane in these systems requires additional voltage to overcome large cathode overpotentials. To eliminate the need for electrical grid energy, we constructed a microbial reverse-electrodialysis methanogenesis cell (MRMC) by placing a reverse electrodialysis (RED) stack between an anode with exoelectrogenic microorganisms and a methanogenic biocathode. In the MRMC, renewable salinity gradient energy was converted to electrical energy, thus providing the added potential needed for methane evolution from the cathode. The feasibility of the MRMC was examined using three different cathode materials (stainless steel mesh coated with platinum, SS/Pt; carbon cloth coated with carbon black, CC/CB; or a plain graphite fiber brush, GFB) and a thermolytic solution (ammonium bicarbonate) in the RED stack. A maximum methane yield of 0.60 ± 0.01 mol-CH4/mol-acetate was obtained using the SS/Pt biocathode, with a Coulombic recovery of 75 ± 2% and energy efficiency of 7.0 ± 0.3%. The CC/CB biocathode MRMC had a lower methane yield of 0.55 ± 0.02 mol-CH4/mol-acetate, which was twice that of the GFB biocathode MRMC. COD removals (89–91%) and Coulombic efficiencies (74–81%) were similar for all cathode materials. Linear sweep voltammetry and electrochemical impedance spectroscopy tests demonstrated that cathodic microorganisms enhanced electron transfer from the cathode compared to abiotic controls. These results show that the MRMC has significant potential for production of nearly pure methane using low-grade waste heat and a source of waste organic matter at the anode.
Co-reporter:Kuichang Zuo, Jiaxiang Cai, Shuai Liang, Shijia Wu, Changyong Zhang, Peng Liang, and Xia Huang
Environmental Science & Technology 2014 Volume 48(Issue 16) pp:9917-9924
Publication Date(Web):July 30, 2014
DOI:10.1021/es502075r
The architecture and performance of microbial desalination cell (MDC) have been significantly improved in the past few years. However, the application of MDC is still limited in a scope of small-scale (milliliter) reactors and high-salinity-water desalination. In this study, a large-scale (>10 L) stacked MDC packed with mixed ion-exchange resins was fabricated and operated in the batch mode with a salt concentration of 0.5 g/L NaCl, a typical level of domestic wastewater. With circulation flow rate of 80 mL/min, the stacked resin-packed MDC (SR-MDC) achieved a desalination efficiency of 95.8% and a final effluent concentration of 0.02 g/L in 12 h, which is comparable with the effluent quality of reverse osmosis in terms of salinity. Moreover, the SR-MDC kept a stable desalination performance (>93%) when concentrate volume decreased from 2.4 to 0.1 L (diluate/concentrate volume ratio increased from 1:1 to 1:0.04), where only 0.875 L of nonfresh water was consumed to desalinate 1 L of saline water. In addition, the SR-MDC achieved a considerable desalination rate (95.4 mg/h), suggesting a promising application for secondary effluent desalination through deriving biochemical electricity from wastewater.
Co-reporter:Jianyu Sun, Kang Xiao, Yinghui Mo, Peng Liang, Yuexiao Shen, Ningwei Zhu, Xia Huang
Journal of Membrane Science 2014 453() pp: 168-174
Publication Date(Web):
DOI:10.1016/j.memsci.2013.11.003
Co-reporter:Shuai Liang, Genggeng Qi, Kang Xiao, Jianyu Sun, Emmanuel P. Giannelis, Xia Huang, Menachem Elimelech
Journal of Membrane Science 2014 463() pp: 94-101
Publication Date(Web):
DOI:10.1016/j.memsci.2014.03.037
Co-reporter:Kang Xiao, Yue-xiao Shen, Shuai Liang, Peng Liang, Xiao-mao Wang, Xia Huang
Journal of Membrane Science 2014 467() pp: 206-216
Publication Date(Web):
DOI:10.1016/j.memsci.2014.05.030
Co-reporter:Kang Xiao;Ying Xu;Shuai Liang;Ting Lei
Frontiers of Environmental Science & Engineering 2014 Volume 8( Issue 6) pp:805-819
Publication Date(Web):2014 December
DOI:10.1007/s11783-014-0756-8
China has been the forerunner of large-scale membrane bioreactor (MBR) application. Since the first large-scale MBR (⩾ 10 000 m3·d−1) was put into operation in 2006, the engineering implementation of MBR in China has attained tremendous development. This paper outlines the commercial application of MBR since 2006 and provides a variety of engineering statistical data, covering the fields of municipal wastewater, industrial wastewater, and polluted surface water treatment. The total treatment capacity of MBRs reached 1 × 106 m3·d−1 in 2010, and has currently exceeded 4.5 × 106 m3·d−1 with ∼75% of which pertaining to municipal wastewater treatment. The anaerobic/anoxic/aerobic-MBR and its derivative processes have been the most popular in the large-scale municipal application, with the process features and typical ranges of parameters also presented in this paper. For the treatment of various types of industrial wastewater, the configurations of the MBR-based processes are delineated with representative engineering cases. In view of the significance of the cost issue, statistics of capital and operating costs are also provided, including cost structure and energy composition. With continuous stimulation from the environmental stress, political propulsion, and market demand in China, the total treatment capacity is expected to reach 7.5 × 106 m3·d−1 by 2015 and a further expansion of the market is foreseeable in the next five years. However, MBR application is facing several challenges, such as the relatively high energy consumption. Judging MBR features and seeking suitable application areas should be of importance for the long-term development of this technology.
Co-reporter:Shuai Liang, Kang Xiao, Jinling Wu, Peng Liang, Xia Huang
Journal of Membrane Science 2014 454() pp: 111-118
Publication Date(Web):
DOI:10.1016/j.memsci.2013.11.037
Co-reporter:Shuai Liang, Yan Kang, Alberto Tiraferri, Emmanuel P. Giannelis, Xia Huang, and Menachem Elimelech
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 14) pp:6694
Publication Date(Web):June 24, 2013
DOI:10.1021/am401462e
Polyvinylidene fluoride (PVDF) has drawn much attention as a predominant ultrafiltration (UF) membrane material due to its outstanding mechanical and physicochemical properties. However, current applications suffer from the low fouling resistance of the PVDF membrane due to the intrinsic hydrophobic property of the membrane. The present study demonstrates a novel approach for the fabrication of a highly hydrophilic PVDF UF membrane via postfabrication tethering of superhydrophilic silica nanoparticles (NPs) to the membrane surface. The pristine PVDF membrane was grafted with poly(methacrylic acid) (PMAA) by plasma induced graft copolymerization, providing sufficient carboxyl groups as anchor sites for the binding of silica NPs, which were surface-tailored with amine-terminated cationic ligands. The NP binding was achieved through a remarkably simple and effective dip-coating technique in the presence or absence of the N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) cross-linking process. The properties of the membrane prepared from the modification without EDC/NHS cross-linking were comparable to those for the membrane prepared with the EDC/NHS cross-linking. Both modifications almost doubled the surface energy of the functionalized membranes, which significantly improved the wettability of the membrane and converted the membrane surface from hydrophobic to highly hydrophilic. The irreversibly bound layer of superhydrophilic silica NPs endowed the membranes with strong antifouling performance as demonstrated by three sequential fouling filtration runs using bovine serum albumin (BSA) as a model organic foulant. The results suggest promising applications of the postfabrication surface modification technique in various membrane separation areas.Keywords: antifouling; fouling; membrane functionalization; nanoparticles; PVDF; superhydrophilic; ultrafiltration;
Co-reporter:Xue Xia, Fang Zhang, Xiaoyuan Zhang, Peng Liang, Xia Huang, and Bruce E. Logan
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 16) pp:7862
Publication Date(Web):July 31, 2013
DOI:10.1021/am4018225
Activated carbon (AC) is a cost-effective catalyst for the oxygen reduction reaction (ORR) in air-cathode microbial fuel cells (MFCs). To enhance the catalytic activity of AC cathodes, AC powders were pyrolyzed with iron ethylenediaminetetraacetic acid (FeEDTA) at a weight ratio of FeEDTA:AC = 0.2:1. MFCs with FeEDTA modified AC cathodes and a stainless steel mesh current collector produced a maximum power density of 1580 ± 80 mW/m2, which was 10% higher than that of plain AC cathodes (1440 ± 60 mW/m2) and comparable to Pt cathodes (1550 ± 10 mW/m2). Further increases in the ratio of FeEDTA:AC resulted in a decrease in performance. The durability of AC-based cathodes was much better than Pt-catalyzed cathodes. After 4.5 months of operation, the maximum power density of Pt cathode MFCs was 50% lower than MFCs with the AC cathodes. Pyridinic nitrogen, quaternary nitrogen and iron species likely contributed to the increased activity of FeEDTA modified AC. These results show that pyrolyzing AC with FeEDTA is a cost-effective and durable way to increase the catalytic activity of AC.Keywords: activated carbon; catalyst; iron ethylenediaminetetraacetic acid; microbial fuel cell; oxygen reduction reaction;
Co-reporter:Xue Xia, Justin C. Tokash, Fang Zhang, Peng Liang, Xia Huang, and Bruce E. Logan
Environmental Science & Technology 2013 Volume 47(Issue 4) pp:2085
Publication Date(Web):January 29, 2013
DOI:10.1021/es3027659
Oxygen-reducing biocathodes previously developed for microbial fuel cells (MFCs) have required energy-intensive aeration of the catholyte. To avoid the need for aeration, the ability of biocathodes to function with passive oxygen transfer was examined here using air cathode MFCs. Two-chamber, air cathode MFCs with biocathodes produced a maximum power density of 554 ± 0 mW/m2, which was comparable to that obtained with a Pt cathode (576 ± 16 mW/m2), and 38 times higher than that produced without a catalyst (14 ± 3 mW/m2). The maximum current density with biocathodes in this air-cathode MFC was 1.0 A/m2, compared to 0.49 A/m2 originally produced in a two-chamber MFC with an aqueous cathode (with cathode chamber aeration). Single-chamber, air-cathode MFCs with the same biocathodes initially produced higher voltages than those with Pt cathodes, but after several cycles the catalytic activity of the biocathodes was lost. This change in cathode performance resulted from direct exposure of the cathodes to solutions containing high concentrations of organic matter in the single-chamber configuration. Biocathode performance was not impaired in two-chamber designs where the cathode was kept separated from the anode solution. These results demonstrate that direct-air biocathodes can work very well, but only under conditions that minimize heterotrophic growth of microorganisms on the cathodes.
Co-reporter:Kang Xiao, Yuexiao Shen, Xia Huang
Journal of Membrane Science 2013 427() pp: 139-149
Publication Date(Web):
DOI:10.1016/j.memsci.2012.09.049
Co-reporter:Peng Liang;Jincheng Wei;Ming Li
Frontiers of Environmental Science & Engineering 2013 Volume 7( Issue 6) pp:913-919
Publication Date(Web):2013 December
DOI:10.1007/s11783-013-0583-3
A scaled up microbial fuel cell (MFC) of a 50 L volume was set up with an oxic-anoxic two-stage biocathode and activated semicoke packed electrodes to achieve simultaneous power generation and nitrogen and organic matter removals. An average maximum power density of 43.1 W·m−3 was obtained in batch operating mode. By adjusting the two external resistances, the denitrification in the A-MFC and power production in the O-MFC could be enhanced. In continuous mode, when the hydraulic retention times were set at 6 h, 8 h and 12 h, the removal efficiencies of COD, NH4+-N and total nitrogen (TN) were higher than 95%, 97%, and 84%, respectively. Meanwhile the removal loads for COD, NH4+-N and TN were10, 0.37 and 0.4 kg·(m3·d)−1, respectively.
Co-reporter:Yue-xiao Shen, Kang Xiao, Peng Liang, Jian-yu Sun, Shi-jie Sai, Xia Huang
Journal of Membrane Science 2012 Volumes 415–416() pp:336-345
Publication Date(Web):1 October 2012
DOI:10.1016/j.memsci.2012.05.017
In order to fill the knowledge gaps between lab/pilot-scale and full-scale operations and contribute basic information to long-term and stable operation of large-scale membrane bioreactors (MBRs), a systematic investigation was first conducted focused on soluble microbial products (SMPs) in 10 large-scale MBRs (capacity over 10,000 m3/d) for municipal wastewater treatment distributed in 4 different areas of China from fall to winter. The majority of these MBR plants had been operated stably for at least 1 year. Fundamental properties of SMPs were investigated, including composition, molecular weight distribution, hydrophobicity, fluorescent characteristics and fouling potential. The results showed that the concentration of SMPs ranged roughly from 5 to 25 mg TOC/L, with the major component being polysaccharides (ca. 3–18 mg/L) followed by humic substances (ca. 2–10 mg/L); while the protein concentration was relatively low (<5 mg/L). The SMPs presented a broad molecular weight distribution from smaller than 1 kDa to over 100 kDa. About half of the SMPs were hydrophilic substances mainly contributed by polysaccharides; humic substances were concentrated in hydrophobic fractions while proteins showed a relatively wide distribution. The fluorescent properties were found to be affected appreciably by the influent quality. The batch fouling tests indicated that the initial fouling rate correlated significantly with SMPs concentrations, which was particularly the case for hydrophilic and large-molecular-weight fractions. These findings may contribute to better understanding of membrane fouling in engineering conditions and assist in long-term and stable operation of full-scale MBRs.Highlights▸ Soluble microbial products (SMPs) in 10 membrane bioreactors (MBRs) were studied. ▸ We found low values of SMPs in the monitored MBRs during fall and winter seasons. ▸ SMPs differed with lab/pilot studies in molecular weight and fluorescent properties. ▸ The current results could add basic knowledge for large-scale MBR's application.
Co-reporter:Shuai Liang, Kang Xiao, Yinghui Mo, Xia Huang
Journal of Membrane Science 2012 Volumes 394–395() pp:184-192
Publication Date(Web):15 March 2012
DOI:10.1016/j.memsci.2011.12.040
Irreversible membrane fouling is harmful for long-term operation of filtration. In this study, a novel anti-irreversible fouling polyvinylidene fluoride (PVDF) membrane was successfully fabricated using the wet phase separation methods. Nano-ZnO, with different dosages ranging from 6.7% to 26.7% (percentage of PVDF weight), was blended as an additive into the membrane matrix for the modification of the internal surfaces of membrane pores. A series of tests, such as filtration experiments, contact angle measurements, scanning electron microscope (SEM)/energy dispersive X-ray spectrometer (EDS) analyses and mechanical tests, were performed to characterize the modified membranes. The multi-cycle filtration experiments showed that the modified PVDF membranes demonstrated significant anti-irreversible fouling property. All the modified membranes achieved almost 100% water flux recovery after physical cleaning, whereas the raw membrane only reached 78% recovery. This promotion might be related to the increase of membrane hydrophilicity. The implantation of nano-ZnO into membrane inner surface (i.e., pore wall), as indicated by SEM/EDS tests, might be responsible for the enhancement of anti-irreversible fouling property. The water permeability of the modified membrane almost doubled by adding 6.7% nano-ZnO which was determined as the optimum dosage (within the dosage range in this study) for PVDF membrane modification. Additionally, the mechanical strength was found reinforced for modified membranes, which should also benefit the filtration application.Graphical abstractHighlights► Nano-ZnO modified PVDF membrane reached 100% water flux recovery. ► The initial flux of modified membrane maintained stable in the long-term operation. ► Moderate modification almost doubled the water permeability. ► Modified internal pores might render enhanced anti-irreversible fouling property.
Co-reporter:Xi Luo, Xiaoxin Cao, Yinghui Mo, Kang Xiao, Xiaoyuan Zhang, Peng Liang, Xia Huang
Electrochemistry Communications 2012 Volume 19() pp:25-28
Publication Date(Web):June 2012
DOI:10.1016/j.elecom.2012.03.004
Utilization of waste heat has attracted increasing attentions due to energy crisis and environmental problems. Efficiency of traditional thermodynamic cycles for waste heat conversion is limited by the temperature of heat sources. We propose here the concept of a novel waste heat conversion system, namely a thermal-driven electrochemical generator (TDEG), which comprises a reverse electrodialysis (RED) stack and a distillation column. By using thermally instable ammonium bicarbonate solutions as working fluids, waste heat can be converted to electricity. The feasibility of NH4HCO3 to generate electricity for TDEG was validated in a RED stack for the first time. Two important operating conditions influencing power output of RED stack, i.e. concentration of low concentration solution and flow rate of feed solutions were optimized to be 0.02 M and 800 mL/min, respectively. A maximum power density of 0.33 W/m2 was obtained for the specific RED stack. Ionic flux efficiency and energy efficiency under the optimal condition were 88% and 31%, respectively. The study lays a foundation for the establishment of the promising TDEG.Highlights► The concept of a novel waste heat conversion system was proposed. ► Feasibility of NH4HCO3 to generate electricity in RED was proved for the first time. ► Two important operating conditions were optimized to obtain a maximum power density. ► Coupling NH4HCO3 with RED is promising for energy utilization.
Co-reporter:Yinghui Mo, Alberto Tiraferri, Ngai Yin Yip, Atar Adout, Xia Huang, and Menachem Elimelech
Environmental Science & Technology 2012 Volume 46(Issue 24) pp:13253-13261
Publication Date(Web):December 3, 2012
DOI:10.1021/es303673p
Carboxyls are inherent functional groups of thin-film composite polyamide nanofiltration (NF) membranes, which may play a role in membrane performance and fouling. Their surface presence is attributed to incomplete reaction of acyl chloride monomers during the membrane active layer synthesis by interfacial polymerization. In order to unravel the effect of carboxyl group density on organic fouling, NF membranes were fabricated by reacting piperazine (PIP) with either isophthaloyl chloride (IPC) or the more commonly used trimesoyl chloride (TMC). Fouling experiments were conducted with alginate as a model hydrophilic organic foulant in a solution, simulating the composition of municipal secondary effluent. Improved antifouling properties were observed for the IPC membrane, which exhibited lower flux decline (40%) and significantly greater fouling reversibility or cleaning efficiency (74%) than the TMC membrane (51% flux decline and 40% cleaning efficiency). Surface characterization revealed that there was a substantial difference in the density of surface carboxyl groups between the IPC and TMC membranes, while other surface properties were comparable. The role of carboxyl groups was elucidated by measurements of foulant-surface intermolecular forces by atomic force microscopy, which showed lower adhesion forces and rupture distances for the IPC membrane compared to TMC membranes in the presence of calcium ions in solution. Our results demonstrated that a decrease in surface carboxyl group density of polyamide membranes fabricated with IPC monomers can prevent calcium bridging with alginate and, thus, improve membrane antifouling properties.
Co-reporter:Jincheng Wei;Dr. Peng Liang;Kuichang Zuo;Dr. Xiaoxin Cao ; Xia Huang
ChemSusChem 2012 Volume 5( Issue 6) pp:1065-1070
Publication Date(Web):
DOI:10.1002/cssc.201100718
Abstract
A simple and low-cost modification method was developed to improve the power generation performance of inexpensive semicoke electrode in microbial fuel cells (MFCs). After carbonization and activation with water vapor at 800–850 °C, the MFC with the activated coke (modified semicoke) anode produced a maximum power density of 74 W m−3, 17 W m−3, and 681 mW m−2 (normalized to anodic liquid volume, total reactor volume, and projected membrane surface area, respectively), which was 124 % higher than MFCs using a semicoke anode (33 W m−3, 8 W m−3, and 304 mW m−2). When they were used as biocathode materials, activated coke produced a maximum power density of 177 W m−3, 41 W m−3, and 1628 mW m−2 (normalized to cathodic liquid volume, total reactor volume, and projected membrane surface area, respectively), which was 211 % higher than that achieved by MFCs using a semicoke cathode (57 W m−3, 13 W m−3, and 524 mW m−2). A substantial increase was also noted in the conductivity, C/O mass ratio, and specific area for activated coke, which reduced the ohmic resistance, increased biomass density, and promoted electron transfer between bacteria and electrode surface. The activated coke anode also produced a higher Coulombic efficiency and chemical oxygen demand removal rate than the semicoke anode.
Co-reporter:Peng Liang, Wenlong Wu, Jincheng Wei, Lulu Yuan, Xue Xia, and Xia Huang
Environmental Science & Technology 2011 Volume 45(Issue 15) pp:6647-6653
Publication Date(Web):June 28, 2011
DOI:10.1021/es200759v
A bioelectrochemical system (BES) can be operated in both “microbial fuel cell” (MFC) and “microbial electrolysis cell” (MEC) modes, in which power is delivered and invested respectively. To enhance the electric current production, a BES was operated in MFC mode first and a capacitor was used to collect power from the system. Then the charged capacitor discharged electrons to the system itself, switching into MEC mode. This alternate charging and discharging (ACD) mode helped the system produce 22–32% higher average current compared to an intermittent charging (IC) mode, in which the capacitor was first charged from an MFC and then discharged to a resistor, at 21.6 Ω external resistance, 3.3 F capacitance and 300 mV charging voltage. The effects of external resistance, capacitance and charging voltage on average current were studied. The average current reduced as the external resistance and charging voltage increased and was slightly affected by the capacitance. Acquisition of higher average current in the ACD mode was attributed to the shorter discharging time compared to the charging time, as well as a higher anode potential caused by discharging the capacitor. Results from circuit analysis and quantitatively calculation were consistent with the experimental observations.
Co-reporter:Xi Chen, Xue Xia, Peng Liang, Xiaoxin Cao, Haotian Sun, and Xia Huang
Environmental Science & Technology 2011 Volume 45(Issue 6) pp:2465-2470
Publication Date(Web):February 15, 2011
DOI:10.1021/es103406m
Microbial desalination cell (MDC) is a new method to obtain clean water from brackish water using electricity generated from organic matters by exoelectrogenic bacteria. Anions and cations, derived from salt solution filled in the desalination chamber between the anode and cathode, move to the anode and cathode chambers under the force of electrical field, respectively. On the basis of the primitive single-desalination-chambered MDC, stacked microbial desalination cells (SMDCs) were developed in order to promote the desalination rate in the present study. The effects of desalination chamber number and external resistance were investigated. Results showed that a remarkable increase in the total desalination rate (TDR) could be obtained by means of increasing the desalination cell number and reducing the external resistance, which caused the charge transfer efficiency increased since the SMDCs enabled more pairs of ions separated while one electron passed through the external circuit. The maximum TDR of 0.0252 g/h was obtained using a two-desalination-chambered SMDC with an external resistance of 10 Ω, which was 1.4 times that of single-desalination-chambered MDC. SMDCs proved to be an effective approach to increase the total water desalination rate if provided a proper desalination chamber number and external resistance.
Co-reporter:Yinghui Mo, Kang Xiao, Yuexiao Shen, Xia Huang
Separation and Purification Technology 2011 Volume 82() pp:121-127
Publication Date(Web):27 October 2011
DOI:10.1016/j.seppur.2011.08.033
It is believed that the presence of calcium ions causes more severe organic fouling during nanofiltration, since they serve as bridges near the membrane surface between foulants and the surface through complexation. However, complexation can also occur in the solution (bulk complexation), leading to the formation of aggregates. This study used alginate as a model foulant to investigate the potential for bulk complexation to lower organic fouling. Results demonstrated that two regimes existed with regard to initial fouling, i.e., flux decline. As the concentration of calcium increases from zero, the initial rate of fouling increased until a critical calcium concentration was reached. Increasing the calcium concentration above this point decreased the initial rate of fouling. Analysis of the size distribution in the alginate solution revealed that at very high calcium concentrations, significant formation of aggregates occurred and reduced the amount of dissolved organic carbon. Thus, effective transportation of alginate toward the membrane and the fouling it causes occur more slowly. The accumulative total organic carbon at the membrane surface was similar to the initial fouling with respect to the concentration of calcium. This strengthens the slower effective transportation of alginate at very high calcium concentrations. Moreover, the stabilized flux and specific resistance of the fouling layer varied monotonically with calcium concentrations over all concentrations tested. Both depend on intermolecular forces between foulants, which is enhanced at increased calcium concentration.Graphical abstractHighlights► Significant aggregation of alginate occurred when Ca2+ was above 3 mM. ► Initial fouling of NF membranes by alginate reduced when Ca2+ was above 3 mM. ► Accumulative TOC at the NF membrane surface reduced when Ca2+ was above 4 mM. ► Stirring the solution has little influence on the aggregation of alginate and Ca2+.
Co-reporter:Peng Liang, Huiyong Wang, Xue Xia, Xia Huang, Yinghui Mo, Xiaoxin Cao, Mingzhi Fan
Biosensors and Bioelectronics 2011 Volume 26(Issue 6) pp:3000-3004
Publication Date(Web):15 February 2011
DOI:10.1016/j.bios.2010.12.002
Carbon nanotube (CNT) is a promising electrode material and has been used as an anode modifier in microbial fuel cells (MFCs). In this study, a new method of simultaneously adding CNT powders and Geobacter sulfurreducens into the anode chamber of a MFC was used, aiming to form a composite biofilm on the anode. The performance of MFCs such as startup time and steady-state power generation was investigated under conditions of different CNT powders dosages. Results showed that both the startup time and the anodic resistance were reduced. The optimal dosage of CNT powders pre-treated by acid was 4 mg/mL for the anode chamber with an effective volume of 25 mL. The anodic resistance and output voltage of the MFC with CNT powders addition were maintained around 180 Ω and 650 mV during 40 days operation, while those of the MFC without CNT powders addition increased from 250 Ω to 540 Ω and decreased from 630 mV to 540 mV, respectively, demonstrating that adding CNT powders helped stabilize the anodic resistance, thus the internal resistance and power generation during long-term operation. Based on cyclic voltammogram, the electrochemical activity of anodic biofilm was enhanced by adding CNT powders, though no significant increase of the biomass in anodic biofilm was detected by phospholipids analysis. There was no remarkable change of ohmic resistance with an addition of CNT powders revealed by current interrupt method, which indicated that the rate of mass transfer might be promoted by the presence of CNT powders.
Co-reporter:Xiaoyuan Zhang, Haotian Sun, Peng Liang, Xia Huang, Xi Chen, Bruce E. Logan
Biosensors and Bioelectronics 2011 30(1) pp: 267-271
Publication Date(Web):
DOI:10.1016/j.bios.2011.09.023
Co-reporter:Kang Xiao, Xiaomao Wang, Xia Huang, T. David Waite, Xianghua Wen
Journal of Membrane Science 2011 373(1–2) pp: 140-151
Publication Date(Web):
DOI:10.1016/j.memsci.2011.02.041
Co-reporter:Yuexiao Shen, Wentao Zhao, Kang Xiao, Xia Huang
Journal of Membrane Science 2010 Volume 346(Issue 1) pp:187-193
Publication Date(Web):1 January 2010
DOI:10.1016/j.memsci.2009.09.040
Soluble microbial products (SMPs) contained in membrane bioreactor (MBR) supernatant have been proved to be main foulants. To obtain a comprehensive understanding of the fouling potential of SMPs on the basis of both hydrophilic/hydrophobic properties and molecular size, MBR supernatant of a pilot-scaled system treating municipal wastewater was partitioned into different hydrophilic/hydrophobic fractions by DAX-8 resins, with joint size partition of hydrophilic fraction also undertaken. A series of stirred dead-end filtration tests were conducted to investigate the flux decline. Hydrophilic fraction was found the dominant foulant responsible for flux deterioration, which was mainly attributed to the subclass of molecular weight above 100 kDa. The molecular weight distribution and atomic force microscopy images indicated that large molecules in hydrophilic fraction plugged the membrane pores. The backwash tests showed the flux decline caused by hydrophilic fraction was much less recoverable by hydraulic cleaning. It can be inferred that steric factor, i.e. size exclusion was the primary cause in the initial stage of fouling, while the role of hydrophobic interaction was of less significance. Additional modeling work indicates that the main fouling mechanism was complete blocking, further confirming the predominance of size exclusion contributing to membrane fouling by SMPs in MBR supernatant.
Co-reporter:Jincheng Wei, Peng Liang, Xiaoxin Cao and Xia Huang
Environmental Science & Technology 2010 Volume 44(Issue 8) pp:3187-3191
Publication Date(Web):March 26, 2010
DOI:10.1021/es903758m
The anode potential in microbial fuel cells (MFCs) defines the possible metabolic energy gain (PMEG) for the bacteria growth. This study focused on the mechanism behind anode potential controlling microbial growth and power generation in MFCs from an energy perspective. Four sets of MFCs were operated with varied conditions: three with different applied anode potential (−160, 0, and 400 mV vs standard hydrogen electrode (SHE)) and one with an external resistor (500 Ω). A model strain Geobacter sulfurreducens was used here. The evolution of biomass was measured and its quantitative relationship with PMEG was analyzed. Linear voltammetry and cyclic voltammetry were also carried out. Results indicated a notable gain in biomass and power density when anode potential increased from −160 to 0 mV. However, no gain in biomass and power generation was detected when anode potential further increased to 400 mV. At anode potential of 0 mV and below, G. sulfurreducens extracted a significant portion of PMEG for growth, while utilization of PMEG significantly decreased at 400 mV. Furthermore, the anode potential has a minor influence on individual G. sulfurreducens cell activity, and the maximum power density of MFC proportionate to biomass.
Co-reporter:Yinghui Mo, Jianhua Chen, Wenchao Xue, Xia Huang
Separation and Purification Technology 2010 Volume 75(Issue 3) pp:407-414
Publication Date(Web):20 November 2010
DOI:10.1016/j.seppur.2010.09.011
Fouling and decline in membrane performance are inevitable during the application of nanofiltration (NF), and cleaning is a vital and effective way to restore membrane performance. In this study on-line and off-line cleaning were investigated to maintain the performance of NF membrane filtrating the effluent from a membrane bioreactor. X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and contact angle analysis were used to characterize the membrane surface for the purpose of choosing proper cleaning agents and assessing the effects of cleaning agents. NaOH was chosen to be the on-line chemical cleaning agent based on the cleaning efficiency compared to other agents tested. After operated at on-line chemical cleaning mode for 24 h membrane was fouled by P, Mg, Fe, Ca from the results obtained by XPS and organic/amino acids from the new absorbance peaks at wave numbers of 2800–3000 cm−1, 1750 cm−1 and 1640 cm−1 obtained by FTIR. Off-line chemical cleaning was performed using citric acid and NaOH in sequence. Acid cleaning was effective for removing P, Mg, Fe, Ca while NaOH cleaning was effective for removing organic/amino acids. The peak strength at wave numbers of 2800–3000 cm−1, 1750 cm−1 and 1640 cm−1, as well as the contact angle, increased after acid cleaning, indicating there might be a coating of inorganic salts on organic foulants, which needed to be removed first so that organic foulant could make good contact with NaOH.Graphical abstractResearch highlights▶ XPS showed P, Mg, Fe, Ca on fouled NF membrane surface. ▶ FTIR showed organic/amino acids on fouled NF membrane surface. ▶ Organic foulants seemed to be coated by a layer of inorganic salts. ▶ Acid cleaning should be performed before alkali cleaning to remove salt coating.
Co-reporter:Xiaoyuan Zhang, Shaoan Cheng, Xia Huang, Bruce E. Logan
Biosensors and Bioelectronics 2010 Volume 25(Issue 7) pp:1825-1828
Publication Date(Web):15 March 2010
DOI:10.1016/j.bios.2009.11.018
Cation (CEMs) and anion exchange membrane (AEMs) are commonly used in microbial fuel cells (MFCs) to enhance Coulombic efficiencies (CEs) by reducing the flux of oxygen through the cathode to bacteria on the anode. AEMs typically work better than CEMs, but in initial experiments we observed the opposite using a membrane electrode assembly MFC. The reason was identified to be membrane deformation, which resulted in water and gas trapped between the membrane and cathode. To correct this, stainless steel mesh was used to press the membrane flat against the cathode. With the steel mesh, AEM performance increased to 46 ± 4 W/m3 in a single cathode MFC, and 98 ± 14 W/m3 in a double-cathode MFC. These power densities were higher than those using a CEM of 32 ± 2 W/m3 (single cathode) and 63 ± 6 W/m3 (double cathode). Higher pH gradients across the membrane and salt precipitation on the cathode were responsible for the reduced performance of the CEM compared to the AEM. CEs reached over 90% for both membranes at >2 A/m2. These results demonstrate the importance of avoiding water accumulation in thin films between membranes and electrodes, and explain additional reasons for poorer performance of CEMs compared to AEMs.
Co-reporter:Xia Huang;Kang Xiao;Yuexiao Shen
Frontiers of Environmental Science & Engineering 2010 Volume 4( Issue 3) pp:245-271
Publication Date(Web):2010 September
DOI:10.1007/s11783-010-0240-z
Since the introduction of the membrane bioreactor (MBR) in China in the early 1990s, remarkable progress has been achieved on the research and application of this technology. China has now become one of the most active fields in the world in this regard. This review outlines the development of MBR-based processes in China and their performance of treating municipal and industrial wastewaters. Since membrane fouling is a critical operational problem with MBR processes, this paper also proposes updated understanding of fouling mechanisms and strategies of fouling control, which are mainly compiled from publications of Chinese researchers. As for the commercial application of MBR in the country, the latest statistics of large-scale MBR plants (>10000 m3·d−1) are provided, and the growth trend of total treatment capacity as well as its driving force is analyzed.
Co-reporter:Xiaoxin Cao, Xia Huang, Peng Liang, Nico Boon, Mingzhi Fan, Lin Zhang and Xiaoyuan Zhang
Energy & Environmental Science 2009 vol. 2(Issue 5) pp:498-501
Publication Date(Web):23 Feb 2009
DOI:10.1039/B901069F
Typical microbial fuel cells (MFCs) rely on precious metals for reduction of oxygen at the cathode, but recently MFCs have been developed that use biocathodes for power generation with alternate electron acceptors. It is shown here that with illumination it is possible to develop a biocathode that uses dissolved carbon dioxide (bicarbonate) as the acceptor. During acclimation, the cathode was set at a potential of 0.242 V (vs.SHE) using a potentiostat. After approximately one month of acclimation, a current of 1 mA was sustained. Bicarbonate was reduced in stoichiometric agreement with current generation, with 0.28 ± 0.02 moles of bicarbonate reduced per mole of electrons. When this biocathode was used in a two-bottle MFC, a power density of 750 mW m−2 was produced. These results demonstrate that MFCs can be used to fix carbon dioxide as well as produce electricity.
Co-reporter:Kang Xiao, Xiaomao Wang, Xia Huang, T. David Waite, Xianghua Wen
Journal of Membrane Science 2009 Volume 342(1–2) pp:22-34
Publication Date(Web):15 October 2009
DOI:10.1016/j.memsci.2009.06.016
Thomas’ model has been applied in this study for the quantitative description and parameterization of the dynamic adsorption of organic foulants to membranes by analysis of the permeate concentration as a function of filtration time (or effluent volume). A hydrophilically enhanced polyvinylidene fluoride (PVDF) membrane was used with dextran (DEX), bovine serum albumin (BSA) and Aldrich humic acid (HA) that were used as model compounds representative of polysaccharides, proteins and humic substances, respectively. Thomas’ model stemming from Langmuirian adsorption kinetics was found to give a good description of physically irreversible membrane fouling as well as the corresponding adsorption constants. The simplification of Langmuirian kinetics to Linear kinetics was found to be reasonable though with no further mathematical simplifications or approximations valid for the case of fouling of a hydrophilically enhanced PVDF membrane. Ka, i.e. the product of the equilibrium constant and the total adsorption capacity, is considered to be a more practicable measure of adsorption affinity than K. The Ka values of 2.09, 2.83 and 3.44 for DEX, BSA and HA, respectively, confirm that the affinity exhibited by foulants typically follows the order: humic substances > proteins > polysaccharides for hydrophilically enhanced PVDF membranes. However, the final adsorbed amount (i.e. the fouling extent) is dependent upon not only the membrane-binding affinity but also the concentration of foulant in the solution.
Co-reporter:Jinling Wu, Xia Huang
Journal of Membrane Science 2009 Volume 342(1–2) pp:88-96
Publication Date(Web):15 October 2009
DOI:10.1016/j.memsci.2009.06.024
In membrane bioreactors, mixed liquor properties influence membrane fouling significantly. An effective method was therefore proposed to identify the major factors that affect membrane fouling under identical conditions for direct comparison. First, the membrane filterability of the mixed liquor was measured to evaluate fouling propensity. Forty mixed liquor samples taken from various membrane bioreactors were measured in terms of their membrane filterability and 14 other properties. The correlation of membrane filterability with each mixed liquor property was further analyzed by multivariate statistical analyses. The results showed that supernatant organic concentration was the most significant factor influencing membrane filterability. The soluble organics and polysaccharides in the supernatant contributed to fouling more than the colloidal organics and proteins. Additionally, mixed liquor suspended solid concentration had an effect on filterability at concentrations greater than 10 g L−1, which resulted in a great increase in the viscosity of the mixed liquor. Otherwise, mixed liquor with mean floc size greater than 80 μm consistently featured good membrane filterability. Extra-cellular polymeric substance content had little effect on membrane filterability.
Co-reporter:Xiaoxin Cao, Xia Huang, Peng Liang, Kang Xiao, Yingjun Zhou, Xiaoyuan Zhang and Bruce E. Logan
Environmental Science & Technology 2009 Volume 43(Issue 18) pp:7148
Publication Date(Web):July 24, 2009
DOI:10.1021/es901950j
Current water desalination techniques are energy intensive and some use membranes operated at high pressures. It is shown here that water desalination can be accomplished without electrical energy input or high water pressure by using a source of organic matter as the fuel to desalinate water. A microbial fuel cell was modified by placing two membranes between the anode and cathode, creating a middle chamber for water desalination between the membranes. An anion exchange membrane was placed adjacent to the anode, and a cation exchange membrane was positioned next to the cathode. When current was produced by bacteria on the anode, ionic species in the middle chamber were transferred into the two electrode chambers, desalinating the water in the middle chamber. Proof-of-concept experiments for this approach, using what we call a microbial desalination cell (MDC), was demonstrated using water at different initial salt concentrations (5, 20, and 35 g/L) with acetate used as the substrate for the bacteria. The MDC produced a maximum of 2 W/m2 (31 W/m3) while at the same time removing about 90% of the salt in a single desalination cycle. As the salt was removed from the middle chamber the ohmic resistance of the MDC (measured using electrochemical impedance spectroscopy) increased from 25 Ω to 970 Ω at the end of the cycle. This increased resistance was reflected by a continuous decrease in the voltage produced over the cycle. These results demonstrate for the first time the possibility for a new method for water desalination and power production that uses only a source of biodegradable organic matter and bacteria.
Co-reporter:Peng Liang;Mingzhi Fan;Xiaoxin Cao
Journal of Chemical Technology and Biotechnology 2009 Volume 84( Issue 5) pp:794-799
Publication Date(Web):
DOI:10.1002/jctb.2114
Abstract
BACKGROUND: The biocathode is proving to be a promising feature for development of the microbial fuel cell (MFC), although much work remains to be done to increase its power generation. This study aimed to enhance the performance of a biocathode by applying selected cathode potential.
RESULTS: When five two-chambered MFCs were operated at selected cathode potentials of 142, 242, 342, 442, or 542 mV (vs standard hydrogen electrode), those MFCs with selected potentials lower than 342 mV could start up, and the highest power density of 0.11 W m−3 was obtained at a selected potential of 242 mV. An inner-biocathode MFC was then constructed and operated at a start-up cathode potential of 242 mV for 30 days. The open circuit cathode potential increased from 477 ± 9 mV to 572 ± 8 mV compared with the potential of the initially abiotic cathode, resulting in an increase in the maximum power density (4.25 ± 0.16 W m−3) of 106%. In addition, tests of continuous operation showed that a loading rate of 135 mg COD L−1 d−1 was optimal for obtaining maximum power generation in the system developed for this study.
CONCLUSION: The results indicated that an optimal cathode potential of 242 mV enhanced the performance of a biocathode using oxygen as the electron acceptor. Copyright © 2009 Society of Chemical Industry
Co-reporter:Yinghui Mo;Peng Liang;Huiyong Wang;Xiaoxin Cao
Journal of Chemical Technology and Biotechnology 2009 Volume 84( Issue 12) pp:1767-1772
Publication Date(Web):
DOI:10.1002/jctb.2242
Abstract
BACKGROUD: A decreased power density could be observed in a single-chamber microbial fuel cell (MFC) with a cation exchange membrane (CEM), as a result of pH-associated problem and a precipitated salt-associated problem, due to the transport of cations other than protons through the membrane to the cathode. To inhibit cation transport and enhance the stability of power generation, an anion exchange membranes (AEM) was applied in a single-chamber MFC.
RESULTS: After 70 days' operation, the power density dropped 29% in the MFC with an AEM (AMFC), smaller than 48% in the MFC with a cation exchange membrane (CMFC). The reason for this difference lay in internal resistance development. Membrane resistance in the AMFC remained the same but that in the CMFC was increased by 67 Ω, and the cathode resistance increase in the AMFC was 54 Ω, while that in the CMFC was 123 Ω. The precipitated cations on the cathode catalyst surface in the CMFC, which accounted for the resistance increase, were up to 84 times larger than that in the AMFC.
CONCLUSION: Because of its capacity for inhibiting cations, the AMFC possessed more stable membrane and cathode resistances; thus an enhanced power generation was obtained. Copyright © 2009 Society of Chemical Industry
Co-reporter:Wen-tao Zhao, Xia Huang, Duu-jong Lee
Separation and Purification Technology 2009 Volume 66(Issue 2) pp:279-286
Publication Date(Web):20 April 2009
DOI:10.1016/j.seppur.2008.12.028
A laboratory-scale anaerobic–anoxic–oxic membrane bioreactor (A1/A2/O-MBR) system was used to treat heavily loaded and toxic coke plant wastewater and operated for more than 500 d. Treatment performance, acute toxicity assessment, and dissolved organic characteristics of the A1/A2/O-MBR system were investigated. The present (A1/A2/O-MBR) system was more efficient and reliable in pollutants and acute toxicity reduction than the conventional anaerobic–anoxic–oxic system tested in parallel as control especially at high and varying loading rates. When the total hydraulic retention times of the A1/A2/O-MBR system was 40 h, the average effluent COD, phenol, NH3-N, TN concentrations and acute toxicity were 264 ± 36 mg/L, 0.2 ± 0.1 mg/L, 0.8 ± 1.0 mg/L, 112 ± 47 mg/L and 0.17 ± 0.01 mg/L (Zn2+ toxicity reference), with removals of 89.8 ± 1.2%, >99.9%, 99.5 ± 0.7%, 71.5 ± 7.8% and 98.3 ± 0.3%, respectively. Hydrophobic/hydrophilic fractionation indicated that the hydrophobic acids were the most abundant fraction of dissolved organic matters in influent and effluent, accounting for 70.3%, 67.2% of total dissolved organic carbon, and 75.0%, 76.2% of total colour intensity, respectively. The hydrophilic substances of the oxic supernatant could be rejected effectively by the membrane. Fluorescence excitation–emission matrix (EEM) analysis suggested that humic substance-like matters were potentially refractory and colour causing matters in coke plant wastewater.
Co-reporter:Wen-Tao Zhao, Xia Huang, Duu-Jong Lee, Xiao-Hui Wang, Yue-Xiao Shen
Journal of Membrane Science 2009 330(1–2) pp: 57-64
Publication Date(Web):
DOI:10.1016/j.memsci.2008.12.072
Co-reporter:Xiaoxin Cao;Xiaoyuan Zhang
Frontiers of Environmental Science & Engineering 2009 Volume 3( Issue 3) pp:307-312
Publication Date(Web):2009 September
DOI:10.1007/s11783-009-0028-1
Current methods for testing the electricity generation capacity of isolates are time- and labor-consuming. This paper presents a rapid voltage testing system of exoelectrogenic bacteria called Quickscreen, which is based on a microliter microbial fuel cell (MFC). Geobacter sulfurreducens and Shewanella baltica were used as the model exoelectrogenic bacteria; Escherichia coli that cannot generate electricity was used as a negative control. It was found that the electricity generation capacity of the isolates could be determined within about five hours by using Quickscreen, and that its time was relatively rapid compared with the time needed by using larger MFCs. A parallel, stable, and low background voltage was achieved using titanium as a current collector in the blank run. The external resistance had little impact on the blank run during the initial period. The cathode with a five-hole configuration, used to hydrate the carbon cathode, gave higher cathode potential than that with a one-hole configuration. Steady discharge and current interrupt methods showed that the anode mostly contributed to the large internal resistance of the Quickscreen system. However, the addition of graphite felt decreased the resistance from 18 to 5 kΩ. This device was proved to be useful to rapidly evaluate the electricity generation capacity of different bacteria.
Co-reporter:Xia Huang, Jinling Wu
Journal of Membrane Science 2008 Volume 318(1–2) pp:210-216
Publication Date(Web):20 June 2008
DOI:10.1016/j.memsci.2008.02.031
The main problem preventing the widespread use of membrane bioreactors (MBR) for wastewater treatment is membrane fouling. In this study, we proposed ozonation as a new method for controlling membrane fouling in MBR. Through a batch test, we found that membrane filterability of the mixed liquor was improved by ozonation with a dosage less than 0.7 mg/g-SS. In a further experiment, an ozonation-coupled MBR and a conventional MBR were run for over 30 days twice, which confirmed the long-term effectiveness of ozone on fouling control. Chemical oxygen demand and ammonia removals in the ozonation-coupled MBR were not affected by ozonation. From the batch test, effects of varying ozone dosages on the mixed liquor properties were measured. When the dosage was less than 0.7 mg/g-SS, extra-cellular polymeric substances were reduced, leading to a slight increase of supernatant organic concentration and more hydrophobic flocs’ surface. Moreover, the zeta-potential of colloids was simultaneously decreased. Enhanced hydrophobicity of the flocs’ surface and decreased zeta-potential of colloids provided a beneficial condition for re-flocculation among bioflocs. After the ozonated mixed liquor was aerated, the flocs re-flocculated. Floc size increased while supernatant organic concentration decreased. These were responsible for improved membrane filterability of the mixed liquor by ozonation.
Co-reporter:Xia Huang, Chun-Hai Wei, Kai-Chang Yu
Journal of Membrane Science 2008 Volume 309(1–2) pp:7-16
Publication Date(Web):15 February 2008
DOI:10.1016/j.memsci.2007.09.069
In an attempt to alleviate membrane fouling, a kind of cylindrical rigid suspended carrier was added in a submerged membrane bioreactor (SMBR) treating synthetic domestic wastewater. Its effect was investigated at different mixed liquor suspended solid (MLSS) concentrations and carrier doses. It was found that the suspended carriers added in the SMBR had two effects on membrane fouling: first was the positive effect by mechanically scouring membrane surface, thereby mitigating cake layer fouling; the second was the negative effect by breaking up sludge flocs that caused an increase in the amount of small particles and supernatant total organic carbon and thus accelerated membrane fouling. The whole effect of suspended carriers on membrane fouling depended on the relative intensity of these two effects. Based on the experimental results of all runs and the inertial lift theory, therefore, it was concluded that there existed an effective carrier dose range for mitigating membrane fouling on the whole. When MLSS concentrations were 5 g/L, 8 g/L, and 11 g/L, then the effective carrier doses (carrier volume vs. total volume) were about less than 4.4%, 7.3%, and 9.5%, respectively.
Co-reporter:Xiaoxin Cao, Xia Huang, Nico Boon, Peng Liang, Mingzhi Fan
Electrochemistry Communications 2008 Volume 10(Issue 9) pp:1392-1395
Publication Date(Web):September 2008
DOI:10.1016/j.elecom.2008.07.008
Microbial fuel cell (MFC) technology is a novel electricity generation process catalyzed by microorganisms. Much progress is made in the design and construction of MFCs, however the diversity of the electrochemically active microorganisms and the electricity generation mechanisms remain a black box. As sun is a predominantly unused energy resource, here we present a highly enriched phototrophic consortium that can produce electricity in an “H” typed MFC at a high power density (2650 mW m−2, normalized to membrane area) in light, which was eightfold of that produced by non-enriched consortium in the same reactor. Light–dark shift experiments showed that light contributed to the electricity generation. A microbial excreted mediator assisted the electron transfer to the electrode. During the experiment, the accumulation of the mediator over time enhanced the electron transfer rate. The excitation–emission matrix fluorescence spectroscopy results indicated indole group containing compound representing the dominant mediator component.
Co-reporter:Chun Liu
Frontiers of Environmental Science & Engineering 2008 Volume 2( Issue 4) pp:
Publication Date(Web):2008 December
DOI:10.1007/s11783-008-0050-8
Bioaugmentation with genetically engineered microorganisms (GEMs) in a membrane bioreactor (MBR) for enhanced removal of recalcitrant pollutants was explored. An atrazine-degrading genetically engineered microorganism (GEM) with green fluorescent protein was inoculated into an MBR and the effects of such a bioaugmentation strategy on atrazine removal were investigated. The results show that atrazine removal was improved greatly in the bioaugmented MBR compared with a control system. After a start-up period of 6 days, average 94.7% of atrazine was removed in bioaugmented MBR when atrazine concentration of influent was 14.5 mg/L. The volumetric removal rates increased linearly followed by atrazine loading increase and the maximum was 65.5 mg/(L·d). No negative effects were found on COD removal although carbon oxidation activity of bioaugmented sludge was lower than that of common sludge. After inoculation, adsorption to sludge flocs was favorable for GEM survival. The GEM population size initially decreased shortly and then was kept constant at about 104–105 CFU/mL. Predation of micro-organisms played an important role in the decay of the GEM population. GEM leakage from MBR was less than 102 CFU/mL initially and was then undetectable. In contrast, in a conventionally activated sludge bioreactor (CAS), sludge bulking occurred possibly due to atrazine exposure, resulting in bioaugmentation failure and serious GEM leakage. So MBR was superior to CAS in atrazine bioaugmentation treatment using GEM.
Co-reporter:Peng Liang;Ming-Zhi Fan;Xiao-Xin Cao
Applied Microbiology and Biotechnology 2007 Volume 77( Issue 3) pp:551-558
Publication Date(Web):2007 December
DOI:10.1007/s00253-007-1193-4
High internal resistance is a key problem limiting the power output of the microbial fuel cell (MFC). Therefore, more knowledge about the internal resistance is essential to enhance the performance of the MFC. However, different methods are used to determine the internal resistance, which makes the comparison difficult. In this study, three different types of MFCs were constructed to study the composition and distribution of internal resistance. The internal resistance (Ri) is partitioned into anodic resistance (Ra), cathodic resistance (Rc), and ohmic resistance (\(R_{\Omega } \)) according to their origin and the design of the MFCs. These three resistances were then evaluated by the “current interrupt” method and the “steady discharging” method based on the proposed equivalent circuits for MFCs. In MFC-A, MFC-B, and MFC-C, the Ri values were 3.17, 0.35, and 0.076 Ω m2, the \(R_{\Omega } \) values were 2.65, 0.085, and 0.008 Ω m2, the Ra values were 0.055, 0.115, and 0.034 Ω m2, and the Rc values were 0.466, 0.15, and 0.033 Ω m2, respectively. For MFC-B and MFC-C, the remarkable decrease in Ri compared with the two-chamber MFC was mainly ascribed to the decline in \(R_{\Omega } \) and Rc. In MFC-C, the membrane electrodes’ assembly lowered the ohmic resistance and facilitated the mass transport through the anode and cathode electrodes, resulting in the lowest Ri among the three types.
Co-reporter:Yujiao Sun;Yong Wang
Frontiers of Environmental Science & Engineering 2007 Volume 1( Issue 2) pp:221-225
Publication Date(Web):2007 May
DOI:10.1007/s11783-007-0038-9
The evolution of activated sludge settleability and its relationship to membrane fouling in a submerged membrane bioreactor were studied at a lab-scale equipment fed with synthetic wastewater. It was found that sludge volume index (SVI) gradually increased and the sludge settleability was reduced, which was caused by the propagation of filamentous bacteria. With increasing SVI, the average increasing rate of trans-membrane pressure increased, the stable filtration period was shortened, and the two stages (smooth stage and accelerating stage) of the trans-membrane pressure were more obvious. At the same time, the increasing rate of trans-membrane pressure at the smooth stage decreased and the rate at the accelerating stage increased with SVI, respectively. The observation by using scanning electronic microscopes showed the cake layer with loose structure and large thickness formed on the membrane surface due to the appearance of filamentous bacteria and high SVI in sludge. Influence of the sludge settleability on the trans-membrane pressure was related to the structure and thickness of the cake layer on the membrane.
Co-reporter:Yanmei Sun, Yue-xiao Shen, Peng Liang, Jizhong Zhou, Yunfeng Yang, Xia Huang
Bioresource Technology (December 2016) Volume 222() pp:
Publication Date(Web):1 December 2016
DOI:10.1016/j.biortech.2016.09.117
•Multiple antibiotic resistance genes were studied by GeoChip in 10 MBRs.•Dominant antibiotic resistance gene groups were different in individual MBR.•Antibiotic resistance genes were majorly from Proteobacteria and Actinobacteria.•Influent, temperature and conductivity affected the resistance gene distribution.Wastewater treatment plants are thought to be potential reservoirs of antibiotic resistance genes. In this study, GeoChip was used for analyzing multiple antibiotic resistance genes, including four multidrug efflux system gene groups and three β-lactamase genes in ten large-scale membrane bioreactors (MBRs) for municipal wastewater treatment. Results revealed that the diversity of antibiotic genes varied a lot among MBRs, but about 40% common antibiotic resistance genes were existent. The average signal intensity of each antibiotic resistance group was similar among MBRs, nevertheless the total abundance of each group varied remarkably and the dominant resistance gene groups were different in individual MBR. The antibiotic resistance genes majorly derived from Proteobacteria and Actinobacteria. Further study indicated that TN, TP and COD of influent, temperature and conductivity of mixed liquor were significant (P < 0.05) correlated to the multiple antibiotic resistance genes distribution in MBRs.
Co-reporter:Peng Liang, Lulu Yuan, Xufei Yang, Xia Huang
Desalination (3 August 2015) Volume 369() pp:68-74
Publication Date(Web):3 August 2015
DOI:10.1016/j.desal.2015.03.029
•The desalination performance of CDI was first simulated based on circuit analysis.•MFC-CDI system could be modeled by a first-order resistor-capacitor circuit.•The model will be helpful for designing and optimizing an MFC-CDI.•The RVD mode delivered a superior performance compared to the SC mode.Using microbial fuel cells (MFCs) to power a capacitive deionization (CDI) process enables simultaneous removal of salinity and organic matter in wastewater. The desalination performance of an MFC-CDI system can be influenced by not only the capacity of individual components but also the arrangement and operation of the MFC-CDI circuit. Five typical circuits (consisting of serial- or parallel-connected MFCs or CDIs) and two ion-desorption modes (short-circuit and reverse-voltage desorption) were compared. Results showed that the MFC-CDI system could be reasonably modeled (R2 > 0.967) by a first-order resistor–capacitor circuit. The optimal arrangement of the MFC-CDI circuit depended on the electrical characteristics of selected MFCs and CDIs as well as operating conditions. When the system was powered by two MFCs of a larger internal resistance (146 Ω), the highest salt removal after 60 min (m60; 7.5 mg) was achieved by paralleling the two MFCs; with MFCs of a smaller resistance (12 Ω) being used, the highest m60 (16.5 mg) was obtained when the two MFCs were connected in series. Further analysis revealed that the MFC's internal resistance and open-circuit voltage, along with the CDI's internal resistance and capacitance, were the chief factors affecting the charge transfer and accordingly desalination on the CDI electrodes.Download full-size image
Co-reporter:Yinghui Mo, Kang Xiao, Yuexiao Shen, Xia Huang
Separation and Purification Technology (27 October 2011) Volume 82() pp:121-127
Publication Date(Web):27 October 2011
DOI:10.1016/j.seppur.2011.08.033
It is believed that the presence of calcium ions causes more severe organic fouling during nanofiltration, since they serve as bridges near the membrane surface between foulants and the surface through complexation. However, complexation can also occur in the solution (bulk complexation), leading to the formation of aggregates. This study used alginate as a model foulant to investigate the potential for bulk complexation to lower organic fouling. Results demonstrated that two regimes existed with regard to initial fouling, i.e., flux decline. As the concentration of calcium increases from zero, the initial rate of fouling increased until a critical calcium concentration was reached. Increasing the calcium concentration above this point decreased the initial rate of fouling. Analysis of the size distribution in the alginate solution revealed that at very high calcium concentrations, significant formation of aggregates occurred and reduced the amount of dissolved organic carbon. Thus, effective transportation of alginate toward the membrane and the fouling it causes occur more slowly. The accumulative total organic carbon at the membrane surface was similar to the initial fouling with respect to the concentration of calcium. This strengthens the slower effective transportation of alginate at very high calcium concentrations. Moreover, the stabilized flux and specific resistance of the fouling layer varied monotonically with calcium concentrations over all concentrations tested. Both depend on intermolecular forces between foulants, which is enhanced at increased calcium concentration.Graphical abstractDownload full-size imageHighlights► Significant aggregation of alginate occurred when Ca2+ was above 3 mM. ► Initial fouling of NF membranes by alginate reduced when Ca2+ was above 3 mM. ► Accumulative TOC at the NF membrane surface reduced when Ca2+ was above 4 mM. ► Stirring the solution has little influence on the aggregation of alginate and Ca2+.
Co-reporter:Tao XUE, Xia HUANG
Journal of Environmental Sciences (2007) Volume 19(Issue 10) pp:1153-1158
Publication Date(Web):1 January 2007
DOI:10.1016/S1001-0742(07)60188-0
AbstractThe releasing characteristics of phosphorus, nitrogen compounds, organics, and some metal cations during thermal treatment of excess sludge were investigated. It was found that during heating not only phosphorus, but also nitrogen compounds, organics, and some metal cations could be released in abundance. The maximum orthophosphate (ortho-P) release of about 90 mg/L in concentration was observed at 50°C in 1 h. Except for volatile fatty acids (VFAs), comparatively little total nitrogen (TN), total organic carbon (TOC), and metal cations were released at the same time. Such results might favor further process of phosphorus recovery. VFAs were considerably released only at 50°C. Acetic, butyric, and propionic acid were the most abundant components in turn and their releasing profiles exhibited good linear relationship with time (R2 = 0.9977, 0.9624, and 0.8908, respectively). The concentrations of Mg2+ and K+ increased with time and temperature during thermal treatment, but Ca2+ decreased. The release of Mg2+ and K+ agreed well with TP release (R2 = 0.9892 and 0.9476, respectively). Temperature in the experimental range had very little impact on the linear relationships, especially of Mg2+. Moreover, the parameter of mixed liquor suspended solids (MLSS) was found to be an important factor for thermal sludge treatment as the released ortho-P and total phosphorus (TP) at 50°C increased more than one-fold when MLSS was increased from 4000 to 8000 mg/L.
Co-reporter:Kang Xiao, Jianyu Sun, Yinghui Mo, Zhou Fang, Peng Liang, Xia Huang, Jianbo Ma, Bingrong Ma
Desalination (16 June 2014) Volume 343() pp:217-225
Publication Date(Web):16 June 2014
DOI:10.1016/j.desal.2013.09.026
•Pore morphology impacts on the interactions between membrane and foulant.•Hydrophobic adsorption and size exclusion are key mechanisms promoting fouling.•PVDF and PTFE/PVDF blend membranes were compared on morphology and fouling.•Thread-like pore walls of the blend membranes discourage hydrophobic adsorption.•High structural complexity of the blend membranes encourages size exclusion.This study provides an insight into the effect of membrane pore morphology on microfiltration organic fouling, by comparing the fouling behaviors of a series of polytetrafluoroethylene/polyvinylidene fluoride (PTFE/PVDF) blend membranes with those of PVDF membranes at varied hydrophobicity and pore size levels. Unlike the PVDF membrane pore morphology which resembled particulate bed, the PTFE/PVDF blend membrane morphology was characterized as fibrous network with thread-like pore walls and interconnected pore channels of high structural complexity. Fouling evolution rate and irreversibility of these membranes were assessed using batch filtration tests, with a membrane bioreactor supernatant employed as the foulant. Fouling of the PVDF membranes deteriorated significantly with increasing hydrophobicity and decreasing pore size. By comparison, all the blend membranes showed moderate fouling, much less sensitive to hydrophobicity and pore size. It was demonstrated that hydrophobicity and pore size pertain to hydrophobic adsorption and size exclusion respectively, which are fundamental membrane–foulant interactions for promoting fouling. Pore morphology may affect fouling by influencing these interactions. For the case of the blend membranes, it was inferred that the thread-like pore walls with limited adsorption area discouraged hydrophobic adsorption, while the high structural complexity encouraged size exclusion on the other hand.Download full-size image
Co-reporter:Qing Wu, Jiali Chang, Xiaoxu Yan, Nuerla Ailijiang, Qiuxiang Fan, Shenghui Wang, Peng Liang, Xiaoyuan Zhang, Xia Huang
Biochemical Engineering Journal (15 February 2016) Volume 106() pp:125-128
Publication Date(Web):15 February 2016
DOI:10.1016/j.bej.2015.11.014
•Bioelectrical reactor (BER) was used to enhance n-damo process.•The best stimulating effect was obtained at 1 V applied.•Continuous electrical exposure mode was more effective than intermittent mode.•The enhancement of nitrite consumption agreed with the methane depletion.As a process utilizing methane as the sole electron source to reduce nitrite, nitrite-dependent anaerobic methane-oxidizing (n-damo) shows high potential to be applied in energy-efficient wastewater treatment. However, the metabolism of n-damo bacteria is far too low for practical application. In this study, bioelectrical reactor (BER) was used to enhance the metabolism. The nitrite removal rate was accelerated under applied electric field. The best stimulating effect was obtained at 1 V applied with the denitrification rate increased to 1.8 fold compared to conventional n-damo process. The enhancement of nitrite consumption was consistent well with the acceleration of methane depletion, further confirmed the electrical stimulation of n-damo process. However, the enhancement could only be realized under continuous electrical exposure mode, rather than intermittent mode. The above results demonstrated that electrical stimulation could lead to an enhanced denitrification of n-damo bacteria.
Co-reporter:Jiao Zhang, Kang Xiao, Peng Liang, T. David Waite, Xia Huang
Desalination (15 August 2014) Volume 347() pp:10-14
Publication Date(Web):15 August 2014
DOI:10.1016/j.desal.2014.05.018
•Electrically released iron affects fouling propensity of soluble microbial product.•Iron and alginate interact through two regimes based on available binding sites.•Certain amount of iron and alginate could form stabilized colloidal particles.•Critical iron demand exists for the purpose of fouling suppression.Iron injection through electrolytically mediated oxidative dissolution of an iron electrode has been proposed as a convenient means of inducing coagulation of wastewater contaminants and thereby reducing the extent of membrane fouling in membrane bioreactors (MBRs). In order to investigate the effect of electrically released iron on membrane fouling propensity, alginate was selected as a model soluble microbial product, and the impact of electrolyzed iron on the specific resistance to filtration (SRF) quantified for a range of electrolysis times. It was confirmed that ferrous iron (Fe(II)) was initially released with concentration increasing proportionally with time of application of electric current in agreement with Faraday's Law. The fouling propensity of alginate increased at early loading times due to the formation of alginate gels and highly stabilized colloidal species. The presence of calcium ions was found to exacerbate this gelation process as a result of i) alginate bridging by Ca2 + ions, and ii) the reduced capacity of the alginate to bind iron and stabilize iron oxide particles. Significant reduction in fouling propensity was observed at higher iron loadings as a result of the formation of substantive amounts of iron oxides which, most likely, adsorbed alginate and prevented gel formation.Download full-size image
Co-reporter:Xia Huang, Peng Liang, Yi Qian
Journal of Biotechnology (10 January 2007) Volume 127(Issue 3) pp:443-451
Publication Date(Web):10 January 2007
DOI:10.1016/j.jbiotec.2006.07.035
Sludge reduction in a conventional activated sludge (CAS) process combined with a recycled sludge reactor where Tubifex tubifex (one of Oligochaeta) was inoculated was investigated in this study. The results showed sludge production could be reduced through T. tubifex's predation on sludge in the recycled sludge reactor. The sludge reduction rate of T. tubifex (R) was from 0.18 to 0.81 mg-VSS mg-Tubifex−1 d−1. The sludge reduction capacity of the recycled sludge reactor E was from 650 to 1080 mg-VSS L−1 d−1. The optimum density of T. tubifex was 2500 mg L−1 and the optimum sludge recycled ratio was 1. The existence of T. tubifex did not affect COD and NH4+-N removals in the process, but led to a slight decrease in TP removal. SVI almost did not change when the T. tubifex density was lower than 3300 mg L−1. The LC50 values on T. tubifex of copper and ammonia were 2.5 and 880 mg L−1, respectively, both of which were higher than those on Aeolosoma hemprichi.
Co-reporter:Yinghui Mo, Kang Xiao, Peng Liang, Xia Huang
Desalination (1 July 2015) Volume 367() pp:103-111
Publication Date(Web):1 July 2015
DOI:10.1016/j.desal.2015.03.036
•The effect of NF membrane fouling on the transport of EDCs was differentiated.•Aqueous transport of EDCs was not affected by fouling due to the thin fouling layer.•Solid transport of EDCs was promoted by fouling (i.e., reduced real rejection).•The reduction of real rejection was dependent on steric hindrance.This paper provides a thorough understanding of the effect of nanofiltration (NF) membrane surface fouling on the two-stage transport of organic micro-pollutants (aqueous transport across the concentration polarization boundary layer and solid transport across the surface fouling layer and membrane), given that the role of each stage has been scarcely explored. The mass transfer coefficient (k), real rejection (Rr), and observed rejection (Robs), were applied to represent the aqueous, solid, and overall transport, respectively. Rejection experiments were conducted with five representative endocrine disrupting compounds (EDCs), subjected to alginate fouling layers with varying properties modulated by Ca2 +. Robs and Rr of EDCs decreased substantially after fouling at high Ca2 + concentrations (> 2 mM), while k changed little, revealing that fouling mainly altered solid transport rather than aqueous transport of EDCs. The reduction in Rr correlated well with the molecular weight of EDCs and the specific resistance of fouling layer, suggesting that steric hindrance of fouling layer was the predominant mechanism affecting solid transport. Additionally, the susceptibility of Rr of EDCs to membrane surface fouling depended on their rejection levels by the virgin membrane.Download full-size image
Co-reporter:Yonghua Yao and Xia Huang
Chemical Communications 2016 - vol. 52(Issue 16) pp:NaN3327-3327
Publication Date(Web):2016/01/15
DOI:10.1039/C5CC09887D
By using an electrochemical strategy, we demonstrated that ferrous ions are capable of decreasing bacterial EET activity in a certain potential range where the conduction-band edge of natural abundant iron(III) oxides is located. It is proposed that ferrous ions enable alteration of the formal potential of outer membrane c-type cytochromes, a crucial protein involved in the EET process.
