| Summary: | 博士 === 國立臺北科技大學 === 環境工程與管理研究所 === 103 === A novel osmotic membrane bioreactor (OsMBR) was proposed for municipal wastewater treatment to simultaneously achieve high water quality, low membrane fouling, and less energy consumption. Three distinct systems of OsMBR, including activated sludge – OsMBR (AS-OsMBR), attached growth biofilm – OsMBR (AGB-OsMBR), and moving bed biofilm reactor – OsMBR (MBBR-OsMBR), were used to study and compare the treatment efficiency. The objectives of this study were focused on (i) investigating the nutrient removal of proposed OsMBR system; (ii) evaluating salt accumulation in bioreactor of proposed OsMBR system; (iii) studying various water fluxes versus time; and (iv) elucidating mechanism of membrane fouling of proposed OsMBR system.
The experimental results showed that the using EDTA sodium coupled with Triton X100 as the draw solution in MBBR-OsMBR system could achieve lowest salt accumulation in bioreactor due to hydrophobic interaction between the tails of Triton X100 and the membrane constricted FO membrane pores, appreciably reducing the reverse salt diffusion of Na+, H[EDTA]3-, and Na[EDTA]3-. That was a good exploration for OsMBR operation to minimize the effect of reverse salt flux and maintain a healthy environment for the microorganism community.
Among proposed OsMBR systems, AGB-OsMBR was recorded to obtain highest nutrient removal (NH4+-N removal of 99.94%, PO43--P of 99.73%). A possible reason for the difference is that the application of biocarrier in AGB-OsMBR within anoxic microorganism community inside and aerobic microorganism community outside of carriers supported for nitrification and denitrification processes occurring well, which resulted in enhanced nutrient removal efficiency. In MBBR-OsMBR system, at a filling rate of 40% (by volume of the bioreactor) of the polyethylene balls used as carriers, NH4+-N and PO43--P were removed corresponding to 99.70% and 99.02% while producing relatively low NO3--N and NO2--N in the effluent (e.g. &;lt; 0.56 and 0.96 mg/L, respectively).
The result also records that the highly charged EDTA coupled with nonionic surfactant (Triton X100) as the draw solution in MBBR-OsMBR system could achieve high recovery efficiency of the diluted draw solution (96%) when using NF-TS80 membrane. An explanation for this phenomenon would be that the gel layer formation from micelle of Triton X100 on NF membrane blocked/constricted membrane pore leading to increasing removal.
As compared with AGB-OsMBR and MBBR-OsMBR, AS-OsMBR was observed to be more serving membrane fouling due to thicker cake layer formation of foulant on FO membrane surface. This demonstrated that adding biocarriers into bioreactor could reduce membrane fouling significantly and maintain stable water flux. Furthermore, the analysis based on Scanning Electron Microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and fluorescence emission-excitation matrix (FEEM) spectrophotometry showed that the proteins and polysaccharides were main fouling components on the FO membrane.
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