在线NaClO反洗对倒置A2O-MBR系统微生物群落的影响

为研究在线NaClO反洗对MBR系统微生物群落结构的影响,采用倒置A2O-MBR反应器分别经历稳定期、在线纯水反洗及在线NaClO反洗阶段,监测系统运行效果、膜污染状况以及微生物群落结构特征.结果表明,在线NaClO反洗阶段反应器对COD、氨氮、TN等的去除效果与反洗前相差无几.在线纯水反洗后平均膜污染速率较稳定期有所降低,而在线NaClO反洗阶段膜污染速率增加,EPS浓度最高,膜污染加剧. Chao指数、Simpson指数和Shannon指数结果表明,在线NaClO反洗后好氧池污泥的微生物多样性几乎不变,而滤饼层污泥的种群丰度略微升高,但微生物的种群多样性明显降低.好氧池和滤饼层污泥的微生物种群主要以变形菌门(Proteobacteria)为主,其次是拟杆菌门(Bacteroidetes).经在线NaClO反洗后,好氧池污泥的变形菌门和拟杆菌门种群相对丰度变化很小,而滤饼层污泥的种群组成变化明显,对氯消毒剂有一定抵抗性的变形菌门从53. 4%增加到77. 8%,而拟杆菌门从33. 4%减少至14. 5%.经在线NaClO反洗后,好氧池和滤饼层在科水平微生物群落分布上十分相似,固氮螺菌科、丛毛单胞菌科等相比NaClO反洗前明显增加,那些能够耐受NaClO处理的微生物种可能是在线NaClO反洗阶段膜污染加剧的主要原因.

Effect of On-line NaClO Backwashing on Microbial Communities in an Inverted A2O-MBR System

To study the effect of on-line NaClO backwashing on the microbial community structure of membrane bioreactor (MBR) systems, a reversed A²O-MBR reactor was used to monitor system performance, membrane fouling, and microbial community structure. Measurements were made during the stabilization stage, the on-line pure water backwashing stage, and the on-line NaClO backwashing stage. The results showed that key system performance indicators during NaClO backwashing stage, such as COD, ammonia nitrogen, and TN treatment efficiency, were similar to previous stages. The average membrane fouling rate during the on-line pure water backwashing period was lower than that of the stable stage, while the membrane fouling rate increased during the on-line NaClO backwashing stage, and EPS concentration was the highest and membrane fouling was aggravated. The results of the Chao index, Simpson index, and Shannon index showed that the microbial diversity in the aerobic tank sludge remained almost stable after on-line NaClO backwashing, while the abundance of cake layer sludge increased slightly, but the microbial diversity decreased significantly. Proteobacteria was the main microbial phylum in both the aerobic tank and cake layer sludge, followed by Bacteroidetes. After on-line NaClO backwashing, the relative abundance of Proteobacteria and Bacteroides in the aerobic tank sludge did not change notably, but the composition of filter cake sludge changed significantly. Proteobacteria that possess resistance to chlorine disinfectant increased from 53.4% to 77.8%, while Bacteroides decreased from 33.44% to 14.5%. After on-line NaClO backwashing, the composition of the microbial community in aerobic tank and cake layer was similar. Azospira and Comamonadaceaea also increased significantly after NaClO backwashing. Microbial species that can tolerate NaClO treatment may be the main cause of membrane fouling.