Burkholderia pseudomallei is a bacteria that is widespread in SE Asia and northern Australia, where there are an average of 16 cases per 100,000 people. This research found that water samples collected in and around Cairns from June to September did NOT contain Burkholderia pseudomallei and led to the conclusion that the risk of infection is much lower than in Darwin or Townsville.

This research was prompted by concerns that rooftop-harvested rainwater fed into household hot water services might expose the public to harmful pathogens such as salmonella. Householders can be exposed to untreated heated rainwater while washing and when this water is used to wash or prepare food. Water heated to 60°C and maintained at this temperature for several minutes’ kills most, but not all infectious pathogens. The problem is that many Australian hot water services operate at lower temperatures that do not kill enteric pathogens. In this study fewer than 5% of water samples collected from unheated rainwater tanks contained pathogens, but this relatively low frequency still poses a risk and is part of the reason that heated rainwater systems fail to meet existing guidelines for safety. Modifications that would improve safety include installing a device that prevents water cooler than 60°C leaving the storage tank and using cold potable water instead of cold rainwater for tempering or in mixer taps. UV disinfection devices attached to rainwater systems are an effective way to reduce health hazards to acceptable levels.

Cryptosporidium, a microscopic pathogen, forms infectious oocysts which are removed by specific and targeted water treatments. Oocysts can only be seen by using a microscope but finding an infectious dose of 10 oocysts in a litre of water is like finding a needle in a haystack. Usually a larger volume of water, 1000mL, is filtered to recover all the oocysts into a small volume of 0.1 to 1 mL, because this is small enough to be examined under a microscope. It is scientific practice to add some dead, colour-dyed oocysts to the large volume of water. If all the coloured oocysts are counted on the filter, the recovery is 100%. From this it became clear that there was a problem with oocyst recovery. This research found that different elements reduced recovery from different types of water, for example, iron and silica reduced oocyst recovery from river or groundwaters. The approved method for quantifying the environmental occurrence of oocysts can now be modified to increase recovery, and this change improves analysis and consequent management which further reduces risks to public health.

The ADWG 2011 lacked objective, quantifiable criteria for measuring pathogen removal from source waters. The WHO requires that health-based targets (HBTs) are used to ensure safe drinking water. HBTs can be set by making ‘Disability Adjusted Life Year’ (DALY) calculations which incorporate information about a population; the average Australian lifespan and the impact of infection on the length of a healthy life. Pathogen levels in water that correspond to micro-DALYs with minimal population-level effects are too low to be detectable by existing tests. This problem is addressed by calculating ‘log removal values’ (LRVs). Pathogens can be measured in source and treated water after the application of a defined method. When 90% of the pathogen is removed, the LRV equals 1, while 99% removal has an LRV of 2. HBTs incorporate LRVs, which are based on objective, quantifiable criteria, to reduce pathogen loads to levels that correspond to acceptable Australian micro-DALY levels. This research collated existing datasets about pathogens in source waters and the efficiency of their removal by treatment plants around Australia. From this, default pathogen levels for a range of Australian source waters and climate events, and LRVs for different treatment methodologies were obtained.

Climate change is depleting water resources, while population increases drive demand for additional recreational facilities, particularly in the vicinity of urban centres. It was thought that public access to water catchment land and reservoirs might cause large-scale outbreaks of disease, and that the water-consuming public would have to pay more for the additional water treatment required to keep drinking water free of the organisms that cause infectious disease. Some consider this unfair because it is an added expense that results from recreational access by a minority of the population. This research considered peer-reviewed literature, policy and regulation, hazard and risk assessment procedures, and placed these in the context of interviews, focus group interactions and surveys. It was concluded that although the science of the adverse effects of recreational access on water quality continues to stand up to examination, there is now justification for conducting an advanced risk-benefit analysis which was developed during the study. This uses a ‘multi-attribute utility’ approach that enables assessment of any given situation by incorporating cross-impact matrices. This risk-benefit methodology addresses the significant issues that arise when adjusting or implementing new recreational access priorities.

Approximately 11% of Australians use rainwater as their main source of potable water but this poses a potential health risk caused by chemical contaminants or microbial pathogens from birds or mammals being washed off the roof. In this study, rainwater samples from 300 households in Adelaide were collected for over a year. There are so many factors affecting a persons’ health that it is not possible to directly correlate water quality to participants health, but there was no significant effect of rainwater on the incidence of gastroenteritis. Levels of lead were higher than recommended by the Australian Drinking Water Guidelines in 2% of the tanks, and bacterial load was higher after rain washed roofs and gutters clean. This led to the recommendation that First Flush devices should be installed to divert early rainfall waters away from storage tanks. Microbial pathogens that cause human gastroenteritis were not detected.

Pathogenic microscopic organisms in source waters pose a risk to public health if water treatment plants do not remove them. It was thought that sensitive PCR tests could be developed to inform decision-making about the most appropriate treatment processes, and to check the absence of pathogens from drinking water. This research focussed on four pathogen classes: cryptosporidium, microcystis, adenovirus and ammonia oxidising bacteria; and evaluated six DNA extraction kits. The Qiagen kit was most cost-effective for extracting DNA and Promega To-Taq polymerase was best for carrying out the PCR test on pathogens in real-world water samples. Other components of the PCR tests that were developed included test controls and DNA standards. A test for each class of pathogen was established and written as a ‘Standard Operating Protocol’ (SOP) which was then applied in different laboratories around Australia. Between-laboratory comparison of results showed the developed PCR tests to be highly reproducible and reliable. They can now be added to the existing suite of tools used to minimise risks to public health.

Cryptosporidium is a waterborne microscopic parasite with different forms at various stages of its lifecycle. One form, the spherical oocyst, is excreted by infected people and transported in rivers and surface waters. The problem is that it is not known if oocysts found in water are dead or are alive and infectious. This leads to an overestimation of the public health risk posed by oocysts found in source waters.

This research developed an in vitro cell culture test to differentiate between dead and infectious oocysts. The immortalised HCT-8 cell line was derived from cancerous human intestinal cells. When the cells are grown in a culture vessel, they display many characteristics of normal human gut cells. It was discovered that treating oocysts with acid to mimic stomach pH and using centrifugal force to ensure oocysts contact the HCT-8 cells, live (but not dead) oocysts react as though they are infecting a human host. The oocysts ‘hatch’ the next sporozoite form of the lifecycle, and these can be counted using a microscope. This ‘infectivity assay’ gives an improved, more accurate method for quantifying risks to human health presented by unidentified cryptosporidium oocysts in water.