| Summary: | 碩士 === 嘉南藥理科技大學 === 環境工程與科學系暨研究所 === 98 === An anoxic-oxic membrane bioreactor (MBR) process is presented to treating high contaminated landfill leachate from An-ding plant. The system operated with total working volume is equal to 18 L which separated into two tanks, the first tank is anoxic condition (6 L) and the second tank is oxic condition (12 L) respectively. Hydraulic retention time (HRT) was set at 2 days and sludge were discharged to maintain solid retention time (SRT) which are equal to 50 days.
The study consisted of three phases. The first phase was operated without anoxic bioreactor. For the second phase operated with anoxic-oxic MBR, 1Q recirculation rate and molasses was supplied in anoxic tank as an extra carbon source for denitrification. The third stage, system had changed the recirculation rate from 1Q to 2Q. At the initial start-up stage, the operation got some problems such as foaming, sludge washed out and poor removal efficiency of chemical oxygen demand (COD) and nitrogen compound which is consider as common operation problems for biological treatment of landfill leachate.
Successive reduction of organic pollutants were achieved after molasses addition, the average mixed liquor volatile suspended solids (MLVSS) and removal efficiency of organic pollutant increased obviously. The sludge in anoxic tank was increased up to the 4,550-9,100 mg/L and 6,175-12,900 mg/L on the second stage and the third stage respectivly. The sludge in oxic tank was increased up to 6,120-10,250 mg/L and 6,125-13,500 mg/L on the second stage and the third stage respectivly. The results of this study illustrated that the highest removal efficiencies of TCOD, SCOD, ammonia nitrogen (NH4+-N) and total nitrogen (TN) were 88%, 86%, 100% and 84%, respectively.
The relationship between foods per mass ratio (F/M ratio), extracellular polymeric substance (EPS) production, mixed liquid suspended solid (MLSS), particle size distribution, specific cake resistance (α) and membrane pore size with modified fouling index (MFI) were found. The MFI is method to measure fouling potential in membrane system. Factors effect to membrane fouling is too complex to explain by only one parameter. The results from this experiment found that, specific cake resistance was increased when MFI increased which results from high MLSS accumulated on membrane surface and may reduce permeate flux and system performance. Also at low F/M ratio, small particle size, high EPS production, high total organic carbon (TOC) concentration in oxic-MBR all are result in high MFI value. The complex relationship between several parameters and MFI was explained by Carmen-Kozeny equation, biomass characteristic and physical operation etc.
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