Characterization of microbial regrowth potential shaped by advanced drinking water treatment

Abstract

Microbial regrowth in premise plumbing is a threat to water safety. Disinfectant residuals are often diminished during water transportation and stagnation, leading to the regrowth of opportunistic pathogens. Although microbial regrowth potential is mostly determined by water treatment, little is known about how each treatment step affects two key factors that contribute to microbial regrowth potential: biodegradable organic matter and microbial abundance. In this study, we operated annular reactors to evaluate the microbial regrowth potential of water shaped after each treatment step in a full-scale drinking water treatment plant with ozonation and biological activated carbon filtration. The assimilable organic carbon and total cell count (TCC) were stable at all treatment steps during the sampling period from July to October 2015. The assimilable organic carbon consumption and TCC net increase in the annular reactors indicated that apparent growth yields (cell number base) of microbial communities were different in each reactor. Regrowth potential evaluated by indigenous microbial community in finished water was reduced to 22% of that in raw water, while 75% of assimilable organic carbon in raw water remained in finished water. It suggested that treatment performance evaluated by indigenous microbial communities was better than that evaluated by assimilable organic carbon.

Ozonation in Wastewater Disinfection

“…Ozonation is very effective to inactivate and decay microbial cells (Hammes et al 2008(Hammes et al , 2010Ramseier et al 2011b), but ozonation increases microbial regrowth potential by generating biodegradable organic matter (BOM), while it decreases microbial abundance. As changes in BOM and microbial community are complicated during the treatment process, little information is available on how microbial regrowth potential is shaped in the water [36]. What is more, ozone is produced on-site, so there are fewer safety issues related to transportation and handling.…”