Research On Membrane Fouling And Characteristics Of EPS In MFC-MBR Coupled System

Membrane Bioreactor（MBR）has a lot of advantages compared with thetraditional wastewater treatments, for example, high organic material removalefficiency, low sludge productivity and excellen effluent quality. But the membranecan be easily fouled by abiotic and biological matter, which Limit the popularizationand application of MBR technology.In ordor to solve the above problem, this study reported a novel system whichcoupled MFCs with MBR through sludge backflow to test the membrane foulingmitigating. We researched the change trend of TMP, characteristic of EPS and thepollution condition of membrane surface and hole in the coupled system comparedwith the conditional MBR, so as to study the mechanism of membrane fouling inMFC-MBR coupled system.The conventional MBR and MFC-MBR coupled system ran for92days steadily,both of the two systems ran two cycles during the92days’ running time. The secondcycle time of the conventional MBR is35days, while that of the MFC-MBRincreased to47days. It indicated that the MFC coupling could alleviate membranefouling in MBR.After analysed the resistence of the fouled membrane of the two systems, wefound that compared with the conventional MBR, the increasing speed of themembrane pore plugging resistance decreased from2.57±10¹⁰m^-1d^-1to1.04±10¹⁰m^-1d^-1. We can also found that the pollution layer on the surface of theconventional MBR is thicker and compacter than MFC-MBR coupled system andthe roughness of the membrane surface in conventional MBR is higher than the later.We can conclud that the backflow of the sludge treated by MFCs can restain theformation of pollution on the membrane surface and in the membrane pore.Compared with the conventional MBR, in MFC-MBR coupled system theconcentration and composition of TB-EPS didn’t have signally change, while theconcentration of S-EPS increased by1.8mg/L, and that of LB-EPS decreased by5.5mg（/g·MLSS）. Furthermore, the p/c value of S-EPS and LB-EPS both decreased.This result indicated that the backflow of the sludge treated by MFCs can decreasedthe concentration of the major organics that can lead to membrane fouling, which isone of the reasons that the membrane fouling can be alleviated.The Organic molecular weight distribution of the LB-EPS and TB-EPS inMFC-MBR both increased. Furthermore, from the result of the FTIR analysis we can see that in MFC-MBR coupled system the intensity of polysaccharose andproteins peaks of LB-EPS and membrane pollutants were weaker than that inconverntional system.From the result of Three-dimensional fluorescence spectra analysis, we can seethat compared with conventional MBR all of the fluorescence peaks of the TB-EPSin MFC-MBR coupled system increased lightly, while that of S-EPS decreased alittle. The amount of tryptophane, tyrosine and humic acid in LB-EPS decreasedmarkedly. Peak of tryptophane in LB-EPS was red-shifted and peaks of tyrosine andhumic acid were blue-shifted compared with conventional MBR, this resultindicated that backflow of sludge treated by MFCs can not only decrease the amountof flourescent substances but also change their structural properties.The results of this research indicated that the characteristics of S-EPS, LB-EPSand TB-EPS in MFC-MBR coupled system were greatly changed due to the MFCscoupling. As a result, the membrane fouling was alleviated effectively. The decreaseof the concentration and p/c value of LB-EPS can improve the properties of sludgeand alleviate the membrane fouling.