| The performance of 3 kinds of advanced treatment to PVA wastewater has studied in this paper,including combining Moving Bed Biofilm Reactor and Dynamic Recirculated Membrane Bioreactor together,uniting Moving Bed Biofilm Reactor and Dynamic Submerged Membrane Bioreactor and connecting them together. Moreover,the optimal operation conditions of the 3 modes of MBBR-DMBR in treating PVA wastewater were investigated respectively.Moving Bed Biofilm Reactor(MBBR) is a new and efficient biofilm reactor for wastewater treatment and has shown many advantages.However,the carrier movement in MBBR is not homogeneous,which results in a large dead space.A new reactor called Membrane-moving bed biofilm reactor was designed by changing the operation manner and reactor configuration of MBBR. Membrane-moving bed biofilm reactor(M-MBBR) is the combination of moving bed biofilm reactor(MBBR) and membrane bioreactor (MBR).By theoretical analysis and experimental research,following conclusions could be drew:The performance of M-MBBR for the treatment of PVA-size wastewater was studied.The reactor's structure was introduced,and the changes of operation conditions including hydraulic retention time,volumetric organic loading and ventilation quantity on the treating effects were investigated.The results showed that if volumetric organic loading varied between 1.4～2.8 kg/(m3.d) in the experiment which was carried out at hydraulic retention time 8 h and gas-water ratio 120:1,the PVA-size wastewater could be most effectively treated and keep stability.Correspondingly,M-MBBR may remove as much as 52.7%and 63.2%of PVA and COD respectively.Under the same feed and operating conditions,membrane permeability and the removal effect of contaminant in the reactor dosing powdered activated carbon(PAC 22 g,4 g/L) and reactor not dosing PAC were studied and compared.Moreover the mechanism that PAC enhance the membrane permeability was analyzed.The results of the test showed that the decreasing rate of membrane flux was much slower in reactor dosing PAC compared with that in the reactor not dosing.And the results also showed that PAC addition not only changed the characteristics of mixed liquor but also reduced the content of extracellular polymeric substances(EPS)and microscopic colloids greatly,so the decline rate of membrane flux delayed significantly,and the higher membrane flux of MBR was maintained for along time.The self-forming dynamic membrane module was made up of common filter cloth with powder activated carbon.Two kinds of membrane modules including a dynamic membrane with using powdered activated carbon and a traditional filter membrane without using powdered activated carbon were compared.The experimental results showed that the self-forming dynamic membrane could not only remove contaminants in wastewater effectively,but also prevent pollutants and microbes diffusing into the interior of the primary membrane so as to mitigate membrane fouling.The experiment ran for 90 days with the stable operational performance.In the case of the membrane flux was 150～200 L/(m2·h),HRT was 8 h,the PVA and COD removal efficiency was 67.2%and 76.6%respectively,NH4+-N removal efficiency was 84.3%.The experiments on the 2μm ceramic membrane are carried out to confirm the running condition of dynamic membrane;moreover,the cleaning-up process of polluted dynamic inorganic membrane are studied.The significant subject of this paper is to find the best running condition in treating secondary effluent and mixed liquor of M-MBBR and the running efficiency of DMBR as well.The permeating flux, COD,PVA,turbidity value and color value are measured during experiments.Kaolin was first chosen as the membraning material,because experiments showed that the kaolin dynamic membrane had high permeating flux and was easy renewed after cleaning.With kaolin Particle size increasing the permeating flux went up correspondingly; considering the rejection of little-size molecule,8000 mesh kaolin was better.The performance of kaolin dynamic membrane formed on a ceramic membrane tube for the treatment of secondary effluent of M-MBBR was studied.The effects of operation conditions including concentration of kaolin suspension,trans-membrane pressure, cross-flow velocity and temperature on permeate flux were investigated, and the optimum parameters were determined.The results showed that if kaolin suspension of 0.6 g/L concentration was used in the experiment which was carried out at 50℃by circulating the wastewater at the trans-membrane pressure of 0.3 MPa and at cross-flow velocity of 3 m/s,the PVA-size wastewater could being the most effectively treated.The corresponding values including turbidity and colour removal rates by dynamic membrane,using equivalent conditions,can approach 94.6%and 87%.Besides,the PVA and COD removal rates obtained from the optimum operating conditions were nearly 90%and 90.7%respectively.Mixed liquor of M-MBBR was treated under the transmembrane pressure of 0.2MPa and at a crossflow velocity of 1 m/s and at the temperature of 60℃.We used the kaolin dynamic membrane to treat a kind of Mixed liquor of M-MBBR in a RMBR that was steadily run in 2 weeks.As a result,the average PVA and COD concentration of system effluent were less than 0.08 g/L and 108 mg/L,respectively. The removal rate of PVA was 80%and the permeating flux in RMBR was higher than in normal MBR system.The polluted ceramic membrane was cleaned by high speed flushing一back flushing一flushing with alkali(0.2 mol/L NaOH) 1 h一flushing with acid(0.1 mol/L HCI)30 min.
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