Abstract：
The detachment of biofilm caused by changes in hydraulic conditions is an essential reason for the pollution of water in the drinking water distribution system (DWDS). In this research, the effect of flow fluctuation on bulk water quality was studied. The turbidity, iron concentration, manganese concentration, the total number of bacteria, biodegradable dissolved organic carbon (BDOC), bacterial community structure, and pathogenic genes in bacteria of bulk water were analyzed. The results indicate that the detachment of biofilm caused by fluctuant flow and reverse flow (especially instant reverse flow) can lead to the pollution of water. Throughout the entire experimental period, the turbidity under fluctuant flow velocity is 4.92%∼49.44% higher than that under other flow velocities. BDOC concentration is 5.68%∼53.99% higher than that under low and high flow velocities. The flow fluctuation increases bacterial regrowth potential (BRP) and reduces the biological stability of the bulk water. Low flow velocity is more conducive to the expression of pathogenic functional genes. In the short term, the water quality under low flow velocity is the best. Nevertheless, in a long-term operation (about seven days later), the water quality under high flow velocity is better than that under other flow velocities. This research brings new knowledge about the fluctuant hydraulic conditions on the bulk water quality within the DWDS and provides data support for stable drinking water distribution.
摘要：
由水力条件的变化引起的生物膜的分离是饮用水分配系统（DWDS）中水污染的根本原因。在这项研究中,研究了流量波动对散装水质的影响。浊度，铁浓度,锰浓度，细菌总数，可生物降解的溶解有机碳（BDOC），细菌群落结构，分析了散装水中细菌的致病基因。结果表明，由波动流和逆流（尤其是瞬时逆流）引起的生物膜分离会导致水的污染。在整个实验期间,波动流速下的浊度比其他流速下的浊度高4.92%~49.44%。BDOC浓度比在低流速和高流速下的浓度高5.68%~53.99%。流动波动增加了细菌再生长潜能(BRP)并降低了主体水的生物稳定性。低流速更有利于致病功能基因的表达。在短期内,低流速下的水质最好。然而，在长期手术中（大约7天后），高流速下的水质优于其他流速下的水质。这项研究带来了有关DWDS内散装水质波动的水力条件的新知识，并为稳定的饮用水分配提供数据支持。
