title: The bacteriological composition of biomass recovered by flushing an operational drinking water distribution system.
abstract: This study investigates the influence of pipe characteristics on the bacteriological composition of material mobilised from a drinking water distribution system (DWDS) and the impact of biofilm removal on water quality. Hydrants in a single UK Distribution Management Area (DMA) with both polyethylene and cast iron pipe sections were subjected to incremental increases in flow to mobilise material from the pipe walls. Turbidity was monitored during these operations and water samples were collected for physico-chemical and bacteriological analysis. DNA was extracted from the material mobilised into the bulk water before and during flushing. Bacterial tag-encoded 454 pyrosequencing was then used to characterize the bacterial communities present in this material. Turbidity values were high in the samples from cast iron pipes. Iron, aluminium, manganese and phosphate concentrations were found to correlate to observed turbidity. The bacterial community composition of the material mobilised from the pipes was significantly different between plastic and cast iron pipe sections (p < 0.5). High relative abundances of Alphaproteobacteria (23.3%), Clostridia (10.3%) and Actinobacteria (10.3%) were detected in the material removed from plastic pipes. Sequences related to Alphaproteobacteria (22.8%), Bacilli (16.6%), and Gammaproteobacteria (1.4%) were predominant in the samples obtained from cast iron pipes. The highest species richness and diversity were found in the samples from material mobilised from plastic pipes. Spirochaeta spp., Methylobacterium spp. Clostridium spp. and Desulfobacterium spp., were the most represented genera in the material obtained prior to and during the flushing of the plastic pipes. In cast iron pipes a high relative abundance of bacteria able to utilise different iron and manganese compounds were found such as Lysinibacillus spp., Geobacillus spp. and Magnetobacterium spp.
authors.affiliation: Pennine Water Group, Department of Civil and Structural Engineering, Sir Frederick Mappin Building, University of Sheffield, Sheffield S1 3JD, UK. Electronic address: i.douterelo@sheffield.ac.uk.
authors.forename: I
authors.initials: I
authors.lastname: Douterelo
authors.affiliation: Pennine Water Group, Department of Civil and Structural Engineering, Sir Frederick Mappin Building, University of Sheffield, Sheffield S1 3JD, UK.
authors.forename: S
authors.initials: S
authors.lastname: Husband
authors.affiliation: Pennine Water Group, Department of Civil and Structural Engineering, Sir Frederick Mappin Building, University of Sheffield, Sheffield S1 3JD, UK.
authors.forename: J B
authors.initials: JB
authors.lastname: Boxall
mesh_terms: D001419:Bacteria / Q000254:growth & development / Q000302:isolation & purification*; D018441:Biofilms; D018533:Biomass; D055598:Chemical Phenomena; D015169:Colony Count, Microbial; D060766:Drinking Water / Q000382:microbiology*; D005843:Geography; D009391:Nephelometry and Turbidimetry; D010802:Phylogeny; D012212:Rheology; D006113:United Kingdom; D014871:Water Microbiology; D014881:Water Supply
chemical_list: D060766:Drinking Water
keywords: Bacteria; Discolouration; Drinking water; Metals; Pipe material