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Nuengjamnong, C.,Cho, J.,Polprasert, C.,Ahn, K.-H. IWA Publishing 2006 Water science & technology--water supply Vol.6 No.1
<P>In this study, the influence of extracellular polymeric substances (EPS) on membrane fouling and cleaning efficiency was investigated during the microfiltration process of a submerged membrane bioreactor (SMBR). Two lab-scale SMBRs with different solids retention time (SRT) were operated and the variation of bound (or extractable) EPS in the activated sludge floc was observed in terms of total organic carbon and protein concentration of the extracted EPS solution. Experimental results showed that as SRT decreases, the amount of bound EPS in the activated sludge floc becomes higher. EPS had a positive influence on specific cake resistance to accelerate the membrane fouling. In order to clean the fouled membrane, de-ionized water flushing, chemical cleaning using sodium hypochlorite (NaOCl), and the combination of water flushing and chemical cleaning were performed. The flux recovery rate was calculated to quantify the cleaning efficiency and a microscopic image using scanning electron microscopy was taken to visualize the cleaning effect. It was found that the water flushing was not highly effective at removing the EPS formed in the cake layer. The chemical cleaning of membrane by 5,000 ppm NaOCl for 3 hours could be more effective to eliminate EPS.</P>
A Comparative Study on the Influence of Effluent Recycles to Duckweed-based Ponds Performance
이승환(S. H. Lee),L. Benjawan,T. Koottatep,C. Polprasert,P. Parkpian 대한환경공학회 2005 대한환경공학회 학술발표논문집 Vol.2005 No.12
Pilot-scale continuous flow duckweed-based ponds (DWBPs) were selected in this study as a dominant natural treatment system in respect to nitrogen removal, recovery and reuse suitable for developing countries. The study aimed to enhance system efficiencies especially on N removal and also to increase system stability, thus effluent recycles was introduced. A pilot-scale DWBPs was fed continuously with domestic wastewater, which had TN loading of approximately 10-60 kg ha(-1)d(-1) and COD loading of 19-120 kg ha(-1)d(-1). Six different treatment conditions were set by varying hydraulic retention time at 8 and 16 days, and each of that had effluent recycle rate (Influent : Effluent) at 1:0, 1:0.5 and 1:1 respectively. After comparing these operations, higher N removal efficiencies were significantly different in the system which had longer retention time and effluent recycles. The optimum operating condition was HRT 16 days with effluent recycles 1:1, in which the mean removals were 54% for TN, 72% for TKN and 73% for NH₄-N. It was found that the removal efficiencies of all N species had no obvious differences with effluent recycles, although they were differences in duckweed growth and system stability.