Influence of cyanobacterial extracellular polymeric substances on the water quality in water supply distribution system

Aiming at the characteristics of free cyanobacterial extracellular polymeric substances (EPS) that are difficult to be removed in conventional water treatment processes, and the residual cyanobacterial EPS are easy to enter the water supply distribution system, the influence of cyanobacterial extracellular polymeric substances (EPS) on the water quality and biological stability of water supply distribution system was studied in this paper. The influence of cyanobacterial EPS on the variation of water quality indices, such as residual chlorine, turbidity, biological stability, organic components, and so on, were mainly analyzed under the different membrane attachment internal pipe condition caused by the service time. Results showed that the cyanobacterial EPS accelerated the decay rate of residual chlorine in the pipeline, led to the turbidity exceeding the upper limit of drinking water standard after 12~24h, reduced the biological stability of the pipeline water, increased BDOC by 37.2~39.5%, increased AOC by 365~393%, and increased the total viable bacteria by 18~20 times in 72 hours. It was clarified that the residual cyanobacterial EPS in the effluent of drinking water treatment plant could still serve as a microbial nutrient substrate and metabolic energy under the premise of residual chlorine in the pipe network during cyanobacteria bloom period, and this promoted the growth and reproduction of bacteria within pipeline, increased the metabolic activity of microorganisms, and stimulated the secretion and release of extracellular organic components of microorganisms, resulting in secondary pollution of the water quality. © 2020, Editorial Board of China Environmental Science. All right reserved.