APPLICATION OF ANAEROBIC MEMBRANE BIOREACTOR TO TREAT LOW STRENGTH WASTEWATER USING NON-WOVEN FILTER AND POLYTETRAFLUOROETHYLENE (PTFE) COMPOSITE MEMBRANE
Abstract:Non-woven fabric filter and poly-tetrafluoroethylene (PTFE) composite membrane were investigated to determine their applicability to treat low strength wastewater in anaerobic membrane bioreactor. Sludge cake resistance of the membrane was quantified using pure water flux of anaerobic sludge cake accumulated on the glass fiber filter of similar pore size. It is hypothesized that the formation of thin cake layer on the porous medium, e.g. non-woven and PTFE acts as a dynamic membrane. Thus, the capture of thin sludge cake inside the non-woven fabric matrix and accumulation on the PTFE membrane surface forms a membrane system equivalent to a commercial membrane system. The permeate quality improves as the cake becomes dense with filtration time. Two anaerobic continuously stirred tank reactor (CSTR) coupled with PTFE film laminated on the non-woven fabric filter were operated to treat synthetic municipal wastewater. Total permeate chemical oxygen demand (COD) concentration was less than 30 mg/L in most cases regardless of hydraulic retention time (HRT) and sludge retention time (SRT). However, soluble COD in the reactor was significantly influenced by the operating conditions. The mean soluble COD in the reactors at an HRT of 12 hr was 53 and 124 mg/L at 25°C and 15°C, respectively, while it increased to 72 and 158 mg/L at HRT of 8 hr. The remaining COD, which was not removed in the bioreactor, might have been removed at the membrane surface by sorption and biodegradation. High biological activity on the membrane surface resulted in a high biofouling potential. Due to low operation cross flow velocity and transmembrane pressure, the particle size distribution was not significantly changed. At low temperature of 15°C, however, more fine particles were observed due to the increase liquid viscosity in the system. Thin sludge film accumulated on the membrane surface also acted as a biofilm bioreactor to remove additional COD in this study.
Document Type: Research Article
Publication date: 2005-01-01
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