Yaobin Lu

Performance of a combined system of microbial fuel cell and membrane bioreactor: wastewater treatment, sludge reduction, energy recovery and membrane fouling.

A novel combined system of sludge microbial fuel cell (S-MFC) stack and membrane bioreactor (MBR) was proposed in this study. The non-consumed sludge in the MBR sludge-fed S-MFC was recycled to the MBR. In the combined system, the COD and ammonia treatment efficiencies were more than 90% and the sludge reduction was 5.1% higher than that of the conventional MBR. Its worth noting that the energy recovery and fouling mitigation were observed in the combined system. In the single S-MFC, about 75 mg L(-1) COD could be translated to electricity during one cycle. The average voltage and maximum power production of the single S-MFC were 430 mV and 51 mWm(-2), respectively. Additionally, the combined system was able to mitigate membrane fouling by the sludge modification. Except for the content decrease (22%), S-MFC destroyed simple aromatic proteins and tryptophan protein-like substances in loosely bound extracellular polymeric substances (LB-EPS). These results indicated that effective wastewater treatment, sludge reduction, energy recovery and membrane fouling mitigation could be obtained in the combined system.

In-situ integration of microbial fuel cell with hollow-fiber membrane bioreactor for wastewater treatment and membrane fouling mitigation

A hollow-fiber membrane bioreactor was integrated with a microbial fuel cell to develop a novel system of MFC-MBR based on the utilization of electricity recovered by the MFC for wastewater treatment improvement and membrane fouling mitigation in the MBR. In this system, a maximum power density of 2.18 W/m(3) and an average voltage output of 0.15 V were achieved at an external resistance of 50 Ω. The removal efficiencies of COD, ammonia nitrogen ( [Formula: see text] ) and total nitrogen (TN) in the MFC-MBR were improved by 4.4%, 1.2% and 10.3%, respectively. It is worth noting that, in addition to reducing the deposition of sludge on the membrane surface by the electric field force, the MFC-MBR also alleviated the membrane fouling by sludge modification. Compared with the control MBR (C-MBR), less loosely bound extracellular polymeric substances (LB-EPS), lower SMPp/SMPc ratio, more homogenized sludge flocs and less filamentous bacteria were obtained in the MFC-MBR, which improved the dewaterability and filterability of the sludge. The cake layer on the membrane formed by the modified sludge was more porous with lower compressibility, significantly enhancing the membrane filterability. A proof of concept of an MFC-MBR was provided and shown to be effective in membrane fouling mitigation with efficient wastewater treatment and energy recovery, demonstrating the feasibility of the minute electricity generated by the MFC for membrane fouling alleviation in the MBR.

Identification of the change in fouling potential of soluble microbial products (SMP) in membrane bioreactor coupled with worm reactor.

This study focused on the effect of predated sludge recycle on the fouling potential of soluble microbial products (SMP) in the MBR coupled with Static Sequencing Batch Worm Reactor (SSBWR-MBR). The S-SMP (SMP in SSBWR-MBR) filtration showed slower diminishing rate of flux than C-SMP (SMP in Control-MBR) filtration, and the standard blocking model showed the most excellent fit (R² = 0.9999) for both C-SMP and S-SMP filtration, confirming that hydrophobic/hydrophilic attractive force was supposed to play a major role in SMP filtration. Based on the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analysis, the decrease in the hydrophobic interactions between SMP and membrane (Adhesion) and between the SMP themselves (Cohesion) was found. The structural parameters analysis indicated the S-SMP fouling layer showed a higher porosity, lower biovolume and thinner average thickness than the C-SMP fouling layer at the end of filtration. Further investigations demonstrated that these changes could be attributed to the lower hydrophobic interaction as the result of the decrease in the relative abundance of unsaturated groups (aromatic protein-like substances) in the S-SMP.

Performance analysis of a combined system of membrane bioreactor and worm reactor: Wastewater treatment, sludge reduction and membrane fouling

A new process that combined a membrane bioreactor (S-MBR) and a novel worm reactor was proposed in this study. The combined system indicated excellent sludge reduction efficiency, wastewater treatment performance and membrane permeability. The sludge reduction percentage of the combined system was about 1.9 times higher than that of the conventional MBR. The chemical oxygen demand (COD) discharge rate in the combined system was only one fourth of that in the conventional MBR, indicating that the COD was removed more thoroughly. Low extracellular polymeric substances level (60-75 μg/mg), low filamentous bacteria level, narrow floc size distribution (distribution spread index of 0.91) and high roundness (0.80 ± 0.10) were observed in the S-MBR sludge. Deposited by this modified sludge, a fouling layer with smaller thickness, larger porosity and less proteins and polysaccharides accumulation was formed in the S-MBR, demonstrating that the combined system was able to alleviate membrane fouling.

Changes in characteristics of soluble microbial products and extracellular polymeric substances in membrane bioreactor coupled with worm reactor: relation to membrane fouling.

The study focused on the membrane fouling mitigation observed in a membrane bioreactor (MBR) coupled with worm reactor system. During the operation time of 100 days, the transmembrane pressure (TMP) in the combined system was maintained less than 5 kPa, while the final TMP in the Control-MBR increased to 30 kPa. The changes in properties of soluble microbial products (SMP) and extracellular polymeric substances (EPS) after worm predation were investigated by means of various analytical techniques. It was found that due to the worm predation, the reduced amount of EPS was far more than the increased amount of SMP leading to a significant decrease of protein-like substances which were dominant in the membrane foulants. Except for the content decrease, worm predation destroyed the functional groups of simple aromatic proteins and tryptophan protein-like substances in EPS, making them have lower tendency attaching to the membrane in the combined system.

Optimization of process conditions with attention to the sludge reduction and stable immobilization in a novel Tubificidae-reactor

A novel Tubificidae-reactor with special porous carrier and combined aeration system was designed to investigate the sludge reduction. The influences of change in frequency of high-intensity aeration (FHIA), dissolved oxygen (DO) content, initial sludge concentration (ISC) and sludge retention time (SRT) on the immobilization of Tubificidae and sludge reduction were evaluated. Furthermore, response surface method was applied to optimize the process conditions using the sludge reduction rate and stable immobilization of worms as the target parameters to optimize, and DO as the control factors to be optimized with the fluctuation of influent ISC, while keeping FHIA and SRT at optimum level. Attractive sludge reduction rate (470 mg L(-1)d(-1)) can be obtained using the strategies indicated by the highly correlated model. The optimum conditions were found to be DO of 1.0-1.6 mg/L and ISC of 3000-4000 mg/L respectively, while keeping FHIA at 12 times/d and SRT at 2d.

Role of extracellular polymeric substances (EPSs) in membrane fouling of membrane bioreactor coupled with worm reactor

This study focused on the effect of worm reactor on the fouling behaviors of extracellular polymeric substances (EPSs) in the MBR coupled with Static Sequencing Batch Worm Reactor (SSBWR-MBR). The filtration tests showed that the C-EPS (EPS in Control-MBR) and S-EPS (EPS in SSBWR-MBR) resulted in 76% and 67% of flux decrement, respectively. On both fouling layers, the preferential accumulation was protein, but the adsorption efficiency for protein in C-EPS was 20% higher than that in S-EPS. In comparison with the membrane fouled by C-EPS, the bio-volume of protein on the membrane fouled by S-EPS reduced 33%, and the protein porosity increased 20%. Meanwhile, the S-EPS approaching the membrane had to overcome×2.4 stronger repulsive interaction energy than C-EPS, and the membrane fouled by S-EPS exhibited relatively smoother compared to that fouled by C-EPS. As a result, the fouling potential of S-EPS was lower than that of C-EPS.

Quantitative analysis of ammonia-oxidizing bacteria in a combined system of MBR and worm reactors treating synthetic wastewater.

The Static Sequencing Batch Worm Reactor (SSBWR) followed by the MBR (S-MBR) is one of the advanced excess sludge treatments. In this paper, the control MBR (C-MBR) and the SSBWR-MBR were operated in parallel to study the changes of NH3-N removal and ammonia oxidizing bacteria (AOB). The results showed that the capacity of NH3-N removal of the S-MBR was improved by the worm reactors along with the operation. The S-MBR was favorable because it selected for the higher activity of the ammonia oxidization and better cells appearance of the sludge. The five species (Nitrosomonas, Betaproteobacteria, Clostridium, Dechloromonas and Bacteria) were found to be significantly correlate with the ammonia oxidization functions and performance of NH3-N removal in the C-MBR and S-MBR. The Nitrosomonas, Betaproteobacteria and Dechloromonas remained and eventually enriched in the S-MBR played a primary role in the NH3-N removal of the S-MBR.

Systematic analysis of biomass characteristics associated membrane fouling during start-up of a hybrid membrane bioreactor using worm reactor for sludge reduction

This study focused on the effect of predated sludge recycle on microbial community development in MBR coupled with Static Sequencing Batch Worm Reactor (SSBWR-MBR). The microbial activities and community were evaluated. The results indicated that the SSBWR-MBR fed with the predated sludge obtained excellent wastewater treatment performance and membrane permeability. In addition, the LIVE/DEAD staining analyses clearly showed that the viability of sludge in SSBWR-MBR was slightly lower than that in Control-MBR, indicating that SSBWR-MBR had a good ability to digest predated sludge. Changed EPS and SMP characteristics and low EPS production, as the major contributors for the mitigated membrane fouling, were closely associated with microbial community development. Denaturing gradient gel electrophoresis (DGGE) analysis revealed that the bacterial communities in the two reactors were different. Further identification of the bacterial populations suggested that decrease of Betaproteobacteria and Gammaproteobacteria and change in Alphaproteobacteria might be responsible for membrane fouling mitigation.