Comparation of the soluble microbial products released by different bacteria and their ability in RO membrane fouling

Reverse osmosis( RO) system are widely used in the reclamation of municipal wastewater,but fouling of RO membrane causes serious negative effects on the operation. Soluble microbial products( SMP) is the key organic matter causing the biofouling of RO membrane. In this study we characterized the SMPs of 2 different bacterial strains isolated from the surface of RO membranes used in municipal wastewater treatment plant,namely Pseudomonas sp.AM1-1 and Chromobacterium sp.AM1-2,and further compared the ability of causing RO membrane fouling by these two kinds of SMPs. It was found that the proportion of polysaccharide and protein in the two kinds of SMPs was approximately 1:1. The molecular weight( MW) of polysaccharides and proteins in the SMPs from AM1-1 showed a bimodal distribution,having a MW less than 10~3 Da or more than 10~5 Da. While MW of polysaccharides in the SMPs from AM1-2 also showed a bimodal distribution,but the majority was more than 10~6 Da and minority was less than 10~3 Da. The MW of proteins in the SMP from AM1-2 is less than 10~3 Da. The results of lab-scale crossflow fouling experiment show that the higher the MW of organic matters in SMP was,the higher risk of organic fouling would be. The proportion of polysaccharide and protein was not the key factor that affected the RO membrane fouling ability of SMPs. Therefore,reducing the amount of organic matters( especially polysaccharides) with high MW in the surface of RO membrane is the key to reduce the risk of RO membrane fouling caused by SMPs.