| As one kind of high efficient wastewater treatment technology, membrane bioreactor (MBR) has many advantages compared with traditional activated sludge process. However, the membrane fouling in the process of separation and relatively high running costs are the main factors restricting its development. Many Researches showed that appending electric field can effectively mitigate membrane fouling but with additional cost.The microorganisms in Microbial fuel cell (MFC) can be used as catalyst for converting chemical energy into electrical energy directly in the process of wastewatar treatment.A new type of single chamber membrane-less microbial fuel cell with continuous flow was adopted y changing the inflow conditions. Then the generated energy was appended to the MBR in the form of electric field, constructing a new type of MFC-MBR integrated system. Compared with conventional MBR (CMBR), the integrated system was effective for membrane fouling mitigation and better wastewater treatment efficiency. The results showed that:(1) The electricity production performance of the MFC in this study could be improved using the wastewater with low concentration of dissolved oxygen. After the inflow water changed from the raw water to the supernatant of anoxic reactor, the voltage of the MFC increased from 0.44±0.02V to 0.52±0.02V and the open circuit voltage increased from 0.49V to 0.65V. What’s more, the maximum power density increased from 45 mW/m to 59 mW/m, increased by 31%. The coulomb efficiency was doubled from 3.87% to about 8.56%.(2) The membrane fouling could be effectively controlled by appending electric field. With the results of FTIR, it could be deduced that the adhesion rate of pollutants including carbohydrates, protein and humic acid was reduced, especially for carbohydrates, leading to the increase of protein/carbohydrates in the cake layer. And the SMP was more likely to adhere to the membrane surface resulting in the membrane fouling compared with EPS.(3) The appended electric field was effective for activated sludge modification, leading to the change of microbial metabolic activity. It could effectively reduce the release of SMPc by 34.5%.The flocculability of activated sludge could be improved by appending electric field. The Zeta potential (absolute value) of activated sludge from MFC-MBR integrated system was 18.2 mV while it of the CMBR was 22.8 mV. And the growth of filamentous bacteria was promoted to a certain degree, thus increasing the floc size and enhancing the performance of flov structure. The average particle size of sludge from MFC-MBR was 138 μm while it of the CMBR was 120 μm. Furthermore, the sludge flocs in the MFC-MBR were more homogenized and the proportion of sludge flocs (particle size less than 50 μm) was effectively reduced by 37.4%.(4) The MFC-MBR integrated system had superior COD removal efficiency with the effluent concentration averaged 38 mg/L, better than that of the CMBR (54 mg/L). With the calculation of energy distribution, only about 0.5% energy of the inflow conversed into electricity. Although the conversion rate form chemical energy to electrical energy is very low, the generated energy was clean and could be directly extracted from the wastewater, slowing down the membrane fouling rate meanwhile.
|
PDF Full Text Request