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The textile industry is one of the major industries of Taiwan but unfortunately it produces toxic and low biodegradable wastewater. To remedy this problem, this study compared the performance of the membrane bioreactor (MBR) and sequencing batch reactor (SBR) processes for treating real textile dyeing wastewater. The microbial diversity of the MBR process was also identified by a combination of culturing methods and molecular biotechnology. The removal efficiencies of the MBR process for color, COD, BOD, and SS were 54, 79, 99, and 100%, respectively, all higher than the corresponding parameters for the SBR process: i.e., 51, 70, 96, and 60%. All the above four parameters for the MBR effluent meet the criteria of the Taiwan EPA, while on the other hand, for the SBR process, only color and COD meet the Taiwan EPA effluent criteria. Furthermore, the genus Microbacterium, in particular Microbacterium aurum, was the most predominant population, accounting for 70.6% of the total isolates, and might be responsible for the degradation of the dyeing wastewater. Another two textile dyeing degradation bacteria, Paenibacillus azoreducens and Bacillus sp., were also observed as predominant bacteria in MBR sludge.

A B S T R AC TIn this study, the characteristics of extracellular polymeric substance (EPS) and the mechanism of fouling formation investigated using a submerged membrane bioreactor system consisting of a polytetrafl uoroethylene (PTFE) membrane. During 85 days of operation, the bound EPS observed as the main component, which contributed major part of resistance to fouling. The protein to carbohydrate ratio was higher in the growth phase than in the stationary phase. The fouling resistances contributed by each individual resistances, i.e. loose cake layer, dense cake layer and internal fouling evaluated by batch fi ltration test after rinse, wash, and backwash operations respectively. The results showed that fouling of membrane and transmembrane pressure increased very quickly within 30 min of operation mainly due to resistance offered by immediate cake layer formation. The analysis of EPS contributed by different fouling layer revealed that most of the carbohydrate adsorbed quickly on the PTFE membrane fi rst and then protein concentration increased with increasing fi ltration time. The protein content of EPS gradually increased when the foulant approach the membrane, whereas carbohydrate content showed opposite trend. Furthermore, the fi ltration of pure bacteria (Ralstonia) showed that most of proteins adsorbed on the membrane surface were hydrophobic and identifi ed its contribution as the biological functions of translation.

The textile industry, which produces toxic and low biodegradable wastewater, is a major industry of Taiwan. Thus, this study compared the performance of the membrane bioreactor (MBR) and sequencing batch reactor (SBR) process for treating real textile dyeing wastewater. The microbial diversity of the MBR process was also identified by a combined culturing method and molecular biotechnology. The results show that the removal efficiencies for color, COD, BOD, and SS with the MBR process were 54, 79, 99, and 100%, respectively, all higher than the corresponding parameters for the SBR process: 51, 70, 96, and 60%. All the above four parameters for the MBR effluent meet the criteria of the Taiwan EPA, while on the other hand for the SBR process, only color and COD meet the Taiwan EPA effluent criteria. Furthermore, the genus Microbacterium, especially the Microbacterium aurum, was the most predominant population, contributing 70.6% of the total isolates, and might be responsible for the degradation of the dyeing wastewater. Another two textile dyeing degradation bacteria, Paenibacillus azoreducens and Bacillus sp., as predominant bacteria in MBR sludge, were also observed.

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