title: Assessing microbiological water quality in drinking water distribution systems with disinfectant residual using flow cytometry.
abstract: Flow cytometry (FCM) as a diagnostic tool for enumeration and characterization of microorganisms is rapidly gaining popularity and is increasingly applied in the water industry. In this study we applied the method to obtain a better understanding of total and intact cell concentrations in three different drinking water distribution systems (one using chlorine and two using chloramines as secondary disinfectants). Chloramine tended to result in lower proportions of intact cells than chlorine over a wider residual range, in agreement with existing knowledge that chloramine suppresses regrowth more efficiently. For chlorinated systems, free chlorine concentrations above 0.5 mg L(-1) were found to be associated with relatively low proportions of intact cells, whereas lower disinfectant levels could result in substantially higher percentages of intact cells. The threshold for chlorinated systems is in good agreement with guidelines from the World Health Organization. The fact that the vast majority of samples failing the regulatory coliform standard also showed elevated proportions of intact cells suggests that this parameter might be useful for evaluating risk of failure. Another interesting parameter for judging the microbiological status of water, the biological regrowth potential, greatly varied among different finished waters providing potential help for investment decisions. For its measurement, a simple method was introduced that can easily be performed by water utilities with FCM capability.
authors.affiliation: Scottish Water, Juniper House, Heriot Watt Research Park, Edinburgh EH14 4AP, United Kingdom.
authors.forename: Simon
authors.initials: S
authors.lastname: Gillespie
authors.affiliation: Cranfield Water Science Institute, Cranfield University, Cranfield, Bedfordshire MK43 0AL, United Kingdom.
authors.forename: Patrick
authors.initials: P
authors.lastname: Lipphaus
authors.affiliation: Scottish Water, Juniper House, Heriot Watt Research Park, Edinburgh EH14 4AP, United Kingdom.
authors.forename: James
authors.initials: J
authors.lastname: Green
authors.affiliation: Scottish Water, Juniper House, Heriot Watt Research Park, Edinburgh EH14 4AP, United Kingdom.
authors.forename: Simon
authors.initials: S
authors.lastname: Parsons
authors.affiliation: Scottish Water, Juniper House, Heriot Watt Research Park, Edinburgh EH14 4AP, United Kingdom.
authors.forename: Paul
authors.initials: P
authors.lastname: Weir
authors.affiliation: Scottish Water, Juniper House, Heriot Watt Research Park, Edinburgh EH14 4AP, United Kingdom.
authors.forename: Kes
authors.initials: K
authors.lastname: Juskowiak
authors.affiliation: Cranfield Water Science Institute, Cranfield University, Cranfield, Bedfordshire MK43 0AL, United Kingdom.
authors.forename: Bruce
authors.initials: B
authors.lastname: Jefferson
authors.affiliation: Cranfield Water Science Institute, Cranfield University, Cranfield, Bedfordshire MK43 0AL, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Jarvis
authors.affiliation: Cranfield Water Science Institute, Cranfield University, Cranfield, Bedfordshire MK43 0AL, United Kingdom. Electronic address: andreas.nocker@gmail.com.
authors.forename: Andreas
authors.initials: A
authors.lastname: Nocker
mesh_terms: D001419:Bacteria / Q000302:isolation & purification*; D002700:Chloramines / Q000032:analysis*; D002713:Chlorine / Q000032:analysis*; D004202:Disinfectants / Q000032:analysis*; D060766:Drinking Water / Q000382:microbiology*; D005434:Flow Cytometry; D060753:Water Quality; D014881:Water Supply
chemical_list: D002700:Chloramines; D004202:Disinfectants; D060766:Drinking Water; D002713:Chlorine
keywords: Chloramine; Chlorine; Disinfection; Distribution system; Drinking water; Regrowth potential