title: Accumulation and fate of microorganisms and microspheres in biofilms formed in a pilot-scale water distribution system.
abstract: The accumulation and fate of model microbial "pathogens" within a drinking-water distribution system was investigated in naturally grown biofilms formed in a novel pilot-scale water distribution system provided with chlorinated and UV-treated water. Biofilms were exposed to 1-mum hydrophilic and hydrophobic microspheres, Salmonella bacteriophages 28B, and Legionella pneumophila bacteria, and their fate was monitored over a 38-day period. The accumulation of model pathogens was generally independent of the biofilm cell density and was shown to be dependent on particle surface properties, where hydrophilic spheres accumulated to a larger extent than hydrophobic ones. A higher accumulation of culturable legionellae was measured in the chlorinated system compared to the UV-treated system with increasing residence time. The fate of spheres and fluorescence in situ hybridization-positive legionellae was similar and independent of the primary disinfectant applied and water residence time. The more rapid loss of culturable legionellae compared to the fluorescence in situ hybridization-positive legionellae was attributed to a loss in culturability rather than physical desorption. Loss of bacteriophage 28B plaque-forming ability together with erosion may have affected their fate within biofilms in the pilot-scale distribution system. The current study has demonstrated that desorption was one of the primary mechanisms affecting the loss of microspheres, legionellae, and bacteriophage from biofilms within a pilot-scale distribution system as well as disinfection and biological grazing. In general, two primary disinfection regimens (chlorination and UV treatment) were not shown to have a measurable impact on the accumulation and fate of model microbial pathogens within a water distribution system.
authors.affiliation: Department of Parasitology, Mycology and Water Microbiology, Swedish Institute for Infectious Disease Control, SE-171 82 Solna, Sweden. jlk@smi.ki.se
authors.forename: Jonas
authors.initials: J
authors.lastname: Långmark
authors.forename: Michael V
authors.initials: MV
authors.lastname: Storey
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Ashbolt
authors.forename: Thor-Axel
authors.initials: TA
authors.lastname: Stenström
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D002713:Chlorine / Q000494:pharmacology; D004202:Disinfectants / Q000494:pharmacology; D004203:Disinfection / Q000379:methods; D004326:Drinking; D016952:Legionella pneumophila / Q000254:growth & development* / Q000302:isolation & purification; D008863:Microspheres; D010865:Pilot Projects; D012483:Salmonella Phages / Q000254:growth & development* / Q000302:isolation & purification; D014466:Ultraviolet Rays; D014871:Water Microbiology; D014881:Water Supply
chemical_list: D004202:Disinfectants; D002713:Chlorine