Estimating the public health risk associated with drinking water in New Zealand : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Massey University, New Zealand

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Massey University
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This thesis is concerned with the application of both epidemiological and molecular tools to assess the drinking water safety in New Zealand. Compromised drinking water safety is commonly manifested as gastrointestinal illness. The studies in this thesis were motivated by the desire to nd ways of reducing the burden of such illness in the human population. Although the studies were conducted in the New Zealand setting the methodologies can be readily applied elsewhere. The rst study investigated the factors associated with the presence of microbes in raw water intended for public consumption. Random forest, an established non-parametric statistical method, was used to model data with possible complex interactions and identi ed variables that were predictive of the presence of microbes in raw drinking water. E. coli, which is widely used as a microbial contamination indicator in the water industry, was found to be a better predictor of the presence/absence of Campylobacter (bacteria) than protozoan microbes (Cryptosporidium and Giardia). This suggests that alternative methods of determining the presence/absence of pathogens in water should be developed. In the second study, the relationship between river ow and reports of cases of gastrointestinal illness was described using the distributed lag modelling approach. This revealed a positive relationship that peaked around 10 days after high ow. Further, the river ow-gastrointestinal illness relationship was stronger in small drinking distribution networks than in large ones. The small drinking water distribution networks could be targetted for facility upgrade in order to enhance their ability to deliver microbiologically safer drinking water. The third study utilised culture-dependent methods to assess the public health risk associated with drinking water supplied at outdoor recreation facilities | campgrounds. Water treatment using methods such as ultra violet and chemical treatment were found to be highly bene cial for the campgrounds to deliver drinking water that was microbiologically safe and compliant with water safety regulations. The pro les and functional factors of drinking water microbial communities are described in the fourth study. Techniques from the fast-growing eld of metagenomics were employed for this purpose. The capability of metagenomic techniques to detect multiple pathogens in a single assay was demonstrated. This has the potential to greatly enhance the speci city and sensitivity of microbial water quality testing.
Listed in 2015 Dean's List of Exceptional Theses
Drinking water, New Zealand, Water quality, New Zealand, Dean's List of Exceptional Theses