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Bacterial growth within a water distribution system

Gibbs, Robyn Anne; (1990) Bacterial growth within a water distribution system. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Bacterial growth in water distribution systems is a common phenomenon which can result in the occurrence of high numbers of bacteria in drinking water. Bacteria which are not enumerated using the coliform test are generally not considered to be of public health significance. However, the general bacterial population of drinking water may cause problems such as tastes and odours, discoloration, growth of aquatic animals, biologically mediated corrosion, interference with coliform testing and the presence of primary or opportunistic pathogens. In this study a number of aspects of bacterial growth in water distribution systems were examined. The study was carried out using an area of a distribution network supplying organically rich treated water. It was found that plate counts in the distribution system showed patterns of spatial and seasonal variation. The spatial variation was most closely related to the chlorine residuals in the water. The chlorophyll a concentration in the eutrophic reservoir supplying the distribution system was the variable most closely related to the seasonal pattern. Trials were carried out to examine the control of bacterial growth by booster disinfection in the distribution system. Free chlorination, chloramination and UV disinfection reduced bacterial numbers considerably, but did not prevent bacterial numbers increasing further through the distribution system. A method for determining assimilable organic carbon (AOC) concentrations was implemented and modified. Neither the seasonal or spatial variation in plate counts was related to the AOC concentrations. Plate count methods were examined and it was found that the R2A medium and spread plate technique with an extended incubation period gave higher counts than the UK standard method. Laboratory experiments confirmed the strong relationship between chlorine residuals and plate counts, and also showed that temperature affected the growth rate but not the maximum yield of bacteria in the water.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Bacterial growth within a water distribution system
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Biological sciences; Applied sciences; Earth sciences; Drinking water
URI: https://discovery.ucl.ac.uk/id/eprint/10110168
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