Comparison of particle associated bacteria from a drinking water treatment plant and distribution reservoirs with different water sources

Comparison of Particle Associated Bacteria from a Drinking Water Treatment Plant and Distribution Reservoirs with Different Water Sources 1Scientific RepoRts | 6 20367 | DOI 10 1038/srep20367 www natu[.]

www.nature.com/scientificreports OPEN received: 24 July 2015 accepted: 31 December 2015 Published: 02 February 2016 Comparison of Particle-Associated Bacteria from a Drinking Water Treatment Plant and Distribution Reservoirs with Different Water Sources G. Liu1,2, F. Q. Ling3, E. J.  van der Mark4, X. D. Zhang1, A. Knezev5, J. Q. J. C. Verberk1, W. G. J.  van der Meer1,2, G. J. Medema1,6, W. T. Liu3 & J. C.  van Dijk1 This study assessed the characteristics of and changes in the suspended particles and the associated bacteria in an unchlorinated drinking water distribution system and its reservoirs with different water sources The results show that particle-associated bacteria (PAB) were present at a level of 0.8–4.5 × 103 cells ml−1 with a biological activity of 0.01–0.04 ng l−1 ATP Different PAB communities in the waters produced from different sources were revealed by a 16S rRNA-based pyrosequencing analysis The quantified biomass underestimation due to the multiple cells attached per particle was ≥ 85% The distribution of the biologically stable water increased the number of cells per particle (from 48 to 90) but had minor effects on the PAB community Significant changes were observed at the mixing reservoir Our results show the characteristics of and changes in suspended PAB during distribution, and highlight the significance of suspended PAB in the distribution system, because suspended PAB can lead to a considerable underestimation of biomass, and because they exist as biofilm, which has a greater mobility than pipe-wall biofilm and therefore presents a greater risk, given the higher probability that it will reach the customers’ taps and be ingested The bacteria are present in different phases, or locations, in drinking water distribution systems, where they can grow and multiply1,2 These phases are: the bulk water (planktonic bacteria that flow through the water main); pipe-wall biofilm (biofilm bacteria that attach to the pipe surface); suspended solids (particle-associated bacteria, or particulate matter, suspended in the water and transported throughout the network); and loose deposits (particle associated bacteria, or particulate matter that is accumulated/retained in the distribution pipes)1–3 Photographic images taken in an operational distribution pipe illustrate the four phases (Fig S1) These phases are dynamically interrelated: depending on the local hydraulic conditions, the loose deposits and pipe-wall biofilm may be resuspended and detached to become suspended solids and reach the customers’ taps, or the suspended solids may settle and accumulate in the distribution pipes as loose deposits1–3 The particles in drinking water distribution systems have primarily been studied in terms of their physiochemical aspects4–6 Only a few studies have examined the organic components of the loose deposits7–10 Although only limited information on the microbial composition of suspended/settled particles has been reported, researchers have found a considerable amount of bacteria associated with loose deposits, including Mycobacteria spp10 Typically, planktonic bacteria (PB) are subject to rapid washout together with bulk water, due to the plug flow conditions1,11 and to the fact that their size (