| Water and energy shortage are two major global challenges. It is meaningful to develop a new process that both captures the inherent energy from the dissolved organic matters and recovers clean water for reuse from domestic wastewater. Microbial fuel cell(MFC), which enables direct conversation of organic matters into useful electricity via microbial-catalyzed redox reaction, is a promising approach for capturing the energy in wastewater and has become one of the research hotspots in environment and energy. However, most of MFC employed abiotic cathodes and proton exchange membrane(PEM) to separate the anodic and cathodic chambers, leading to high cost and easily polluted. Additionally, MFC, as a bio-membrance reactor, has a negative effect on particulate pollutants removal compared with dissolved organic pollutants removal, leading to low treatment efficiency and poor effluent quality. As a result, these factors greatly limit MFCs’practical application.In this work, a novel overflow-type MFC, which employed a biological cathode and utilized the flow regime of the system to ignore PEM, was developed to lower the cost. Considering the overflow-type MFC’s negative effect on particulate pollutants removal, a novel overflow-type MFC-MBR intergrated system, which took advantage of membrane bioreactor(MBR) and MFC, was developed and showed a good electricity generation performance and pollutants removal. Finally, the in-situ membrane fouling controlled by the generated electricity was investigated, and the mechanisms of membrane fouling mitigation were elucidated. The main results are summarized as following:1. A novel overflow-type MFC was developed and its performance was evaluated. This system could restrict oxygen to transfer from cathodic chamber to anodic chamber which guaranteed anodic chamber anaerobic environment, and maked the wastewater overflow from anodic chamber to cathodic chamber with proton. Results implied that the maximum power density of 697 mW/m3 was obtained. The removal efficiencies of chemical oxygen demand(COD), ammonia nitrogen(NH4+-N) and total nitrogen(TN) were 94.9%,97.1% and 73.8%, respectively. Additionally, the microbial community composition of anodic chamber and cathodic chamber showed that the electrochemically active bacteria were abundant in the electrodes and stimulated by electricity, and involved in electricity generation and pollutants removal.2. A novel overflow-type MFC-MBR intergrated system was developed and its performance was evaluated. In this system, the stainless steel(SS) mesh with biofilm formed on it served as the biocathode and filtration material, which realized high effluent quality and energy recovery. Results implied that the maximum power density of 629 mW/m3 was obtained. The effluent turbidity dropped to 2.53 NTU from 20.3 NTU in one day. The removal efficiencies of chemical oxygen demand(COD), ammonia nitrogen(NH4+-N) and total nitrogen(TN) were 99.2%,99.5% and 84.9%, respectively. Additionally, the microbial community composition of the biofilm in the biocathode showed that the denitrifying bacteria might be the electrochemically active bacteria or stimulated by electricity, which were abundant in the biofilm and contributed to electron acceptance from the cathode electrode under the electron transfer mediation of Lactococcus.3. A novol concept for in-situ membrane fouling control in the overflow-type MFC-MBR intergrated system was proposed. In this study, the characteristics of membrane fouling and the parameters of mixed liquor were measured. Results implied that the membrane fouling rate was greatly reduced in the overflow-type MFC-MBR intergrated system, and under the interaction of the formed electric filed, bacteria stimulated by electricity and H2O2 produced by the biocathode, the properties of the sludge had changed, including particle zeta potential decrease, particle size distribution macroaggregation, soluble microbial products (SMP) and extracellular polymeric substances (EPS) reduction and SMPp/SMPc ratio increase. The mechanisms about how the membrane fouling was suppressed in this system were elucidated. Results implied that the electric filed formed near by the SS biocathode could reduce the deposition of sludge on the membrane surface, and H2O2 produced by the biocathode could remove the membrane foulants, and the properties of the sludge had changed under the interaction of the formed electric filed, bacteria stimulated by electricity and H2O2 produced by the biocathode to mitigate membrane fouling. |
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