热电厂双膜法中水深度处理回用系统膜污染机制分析

Membrane fouling characterization and mechanism of a full-scale dual membrane process for advanced treatment and reuse of reclaimed water in a thermal power plant

以某热电厂实际规模的双膜法中水回用系统为考察对象,对膜污染结构、形貌、组成与特征进行了研究。结果表明:污染物以有机-无机-微生物复合形式存在,形成致密的膜污染层,无机物主要以P、S、Ca、Si、Mg为主,存在垂直分布特征;有机污染物以腐殖质类、蛋白质、微生物代谢产物为主,且研究发现RO过程富里酸类物质主要为微生物源。碱性清洗液具有更佳的膜污染清洗效果。通过分析可知:微生物污染是膜污染暴发的关键原因,其以杆菌和球菌为主,且具有显著的垂直分布特征;表层微生物主要是α和β变形菌,底层中γ变形菌丰度显著增加。微生物污染垂直分布的主要原因是杀菌和化学清洗过程的选择作用,γ变形菌是先锋微生物,是形成稳定膜污染层的关键物种。因此,控制微生物的滋生是RO中水深度处理的关键,这个过程主要包括预处理工艺的选择和优化杀菌、阻垢和化学清洗策略等。

Membrane fouling is a key issue in reclaimed water reuse with reverse osmosis(RO),but the fouling characterization and mechanism are still lacking for a full-scale RO water reuse system.In this study,a full-scale dual-membrane process for reclaimed water reuse in thermal power plant in China was taken as an object to investigate the structure,morphology,composition and characterization of membrane fouling.The results showed that the tight fouling layer was formed by the combination of inorganic and organic matters(OMs),as well as microbes.The main inorganic components were P,S,Ca,Si,Mg,which presented a vertical distribution in the fouling layer.The organic fouling matters were mainly identified as humic substances,proteins and microbial metabolites,while microbe-derived fulvic acid was the key OM in RO process.Alkaline reagent showed a better cleaning performance for membrane fouling.Furthermore,biofouling was the key reason for the outbreak of membrane fouling,and rod-and spherical-shaped bacteria was the main fouling matters.A remarkable vertical distribution was found for microbial community,α-andβ-proteobacteria showed high abundance on the surface of fouling layer,whileγ-proteobacteria was the leading bacteria on the bottom.The sterilization and chemical cleaning process played the selection role for the vertical distribution formation,andγ-proteobacteria was the pioneering and key bacterium for the stable fouling occurrence due to its strong bactericide tolerance.Thus,bacteria control is a pivotal process for operation of a full-scale RO reclamation system,which includes pretreatment technology selection and sterilization,scale inhibition,and chemical cleaning strategies optimization.