Kuichang Zuo

Microbial desalination cells packed with ion-exchange resin to enhance water desalination rate

A novel configuration of microbial desalination cell (MDC) packed with ion-exchange resin (R-MDC) was proposed to enhance water desalination rate. Compared with classic MDC (C-MDC), an obvious increase in desalination rate (DR) was obtained by R-MDC. With relatively low concentration (10-2 g/L NaCl) influents, the DR values of R-MDC were about 1.5-8 times those of C-MDC. Ion-exchange resins packed in the desalination chamber worked as conductor and thus counteracted the increase in ohmic resistance during treatment of low concentration salt water. Ohmic resistances of R-MDC stabilized at 3.0-4.7 Ω. By contrast, the ohmic resistances of C-MDC ranged from 5.5 to 12.7 Ω, which were 55-272% higher than those of R-MDC. Remarkable improvement in desalination rate helped improve charge efficiency for desalination in R-MDC. The results first showed the potential of R-MDC in the desalination of water with low salinity.

A ten liter stacked microbial desalination cell packed with mixed ion-exchange resins for secondary effluent desalination.

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.

Competitive migration behaviors of multiple ions and their impacts on ion-exchange resin packed microbial desalination cell.

Mixed ion-exchange resins packed microbial desalination cell (R-MDC) could stabilize the internal resistance, however, the impacts of multiple ions on R-MDC performance was unclear. This study investigated the desalination performance, multiple ions migration behaviors and their impacts on R-MDCs fed with salt solution containing multiple anions and cations. Results showed that R-MDC removed multiple anions better than multiple cations with desalination efficiency of 99% (effluent conductivity <0.05 ms/cm) at hydraulic retention time of 50 h. Competitive migration order was SO4(2-)>NO3(-)>Cl(-) for anions and Ca(2+)≈Mg(2+)>NH4(+)>Na(+) for cations, jointly affected by both their molar conductivity and exchange selectivity on resins. After long-term operation, the existence of higher concentration Ca(2+) and Mg(2+) caused the electric conductivity of mixed resins decrease and scaling on the surface of cation-exchange membrane adjoined with cathode chamber, suggesting that R-MDC would be more suitable for desalination of water with lower hardness.

Reducing aeration energy consumption in a large-scale membrane bioreactor: Process simulation and engineering application.

Reducing the energy consumption of membrane bioreactors (MBRs) is highly important for their wider application in wastewater treatment engineering. Of particular significance is reducing aeration in aerobic tanks to reduce the overall energy consumption. This study proposed an in situ ammonia-N-based feedback control strategy for aeration in aerobic tanks; this was tested via model simulation and through a large-scale (50,000 m(3)/d) engineering application. A full-scale MBR model was developed based on the activated sludge model (ASM) and was calibrated to the actual MBR. The aeration control strategy took the form of a two-step cascaded proportion-integration (PI) feedback algorithm. Algorithmic parameters were optimized via model simulation. The strategy achieved real-time adjustment of aeration amounts based on feedback from effluent quality (i.e., ammonia-N). The effectiveness of the strategy was evaluated through both the model platform and the full-scale engineering application. In the former, the aeration flow rate was reduced by 15-20%. In the engineering application, the aeration flow rate was reduced by 20%, and overall specific energy consumption correspondingly reduced by 4% to 0.45 kWh/m(3)-effluent, using the present practice of regulating the angle of guide vanes of fixed-frequency blowers. Potential energy savings are expected to be higher for MBRs with variable-frequency blowers. This study indicated that the ammonia-N-based aeration control strategy holds promise for application in full-scale MBRs.

Carbon filtration cathode in microbial fuel cell to enhance wastewater treatment

A homogeneous carbon membrane with multi-functions of microfiltration, electron conduction, and oxygen reduction catalysis was fabricated without using noble metals. The produced carbon membrane has a pore size of 553nm, a resistance of 6.0±0.4Ωcm(2)/cm, and a specific surface area of 32.2m(2)/g. After it was assembled in microbial fuel cell (MFC) as filtration air cathode, a power density of 581.5mW/m(2) and a current density of 1671.4mA/m(2) were achieved, comparable with previous Pt air cathode MFCs. The filtration MFC was continuously operated for 20days and excellent wastewater treatment performance was also achieved with removal efficiencies of TOC (93.6%), NH4(+)-N (97.2%), and total nitrogen (91.6%). In addition, the carbon membrane was much cheaper than traditional microfiltration membrane, suggesting a promising multi-functional material in wastewater treatment field.

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

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

A Single‐Use Paper‐Shaped Microbial Fuel Cell for Rapid Aqueous Biosensing

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 Ag2 O-coated carbon cathode, and a micrometer-thin porous polyvinylidene fluoride (PVDF) separator are investigated to address the classical MFC issues. The Ag2 O-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.

A Novel Electrochemical Reactor for Nitrogen and Phosphorus Recovery from Domestic Wastewater

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.

Carbonization and Activation of Inexpensive Semicoke‐Packed Electrodes to Enhance Power Generation of Microbial Fuel Cells

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 Wm(-3) , 17 Wm(-3) , and 681 mWm(-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 Wm(-3) , 8 Wm(-3) , and 304 mWm(-2) ). When they were used as biocathode materials, activated coke produced a maximum power density of 177 Wm(-3) , 41 Wm(-3) , and 1628 mWm(-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 Wm(-3) , 13 Wm(-3) , and 524 mWm(-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.

A novel multi-stage microbial desalination cell for simultaneous desalination and enhanced organics and nitrogen removal from domestic wastewater

Conventional microbial desalination cells (MDCs) can extract organic energy from wastewater for in situ utilization in saline water desalination, but are mostly unable to achieve enhanced treatment and desalination for one stream of wastewater. In this study, a multi-stage MDC (M-MDC) with two alternating anodes and cathodes was fabricated, and operated with domestic wastewater in two operational modes. In ACAC operational mode, with wastewater flowing serially from anode-1 → cathode-1 → anode-2 → cathode-2, the M-MDC realized current production of 11.4 mA and desalination efficiency of 52.4%, effluent chemical oxygen demand and total nitrogen removed 92.5% and 87.0% respectively, due to cooperative biological nitrification/denitrification and electrical migration. As a contrast in AACC mode, with wastewater flowing serially from anode-1 → anode-2 → cathode-1 → cathode-2, a higher current generation (17.2 mA) and desalination efficiency (56.4%) were achieved, due to enhanced utilization of wastewater organics in the anode chambers. The M-MDC realized simultaneous self-driven desalination and organics/nitrogen removal for the same stream of domestic wastewater, and various operation modes were proposed for enhanced wastewater treatment (ACAC mode) or energy recovery (AACC mode), indicating a promising potential for the M-MDC in simultaneous treatment and desalination of domestic wastewater.