Water treatment plants (WTP) produce safe drinking water that does not contain harmful microscopic pathogens, but subsequent pipe-leaks or valve or hydrant malfunctions en route to the customers tap increase the risk of pathogens entering the public water supply. International studies indicate a small increase in gastroenteritis for some customers downstream of mains pipeline breaks and repairs. This research compiled Australian cases and found that health risks are probably lower than international examples for many reasons, including that sewer and drinking water pipes tend not to be laid in the same trench. After improving understanding regarding the contamination risks of renewal and water main repair activities in Australia, a control and management framework was produced in accordance with the ADWG. This gives guidance to water utilities about staff training, risk assessment and optimal documentation processes for dynamic site evaluations and repair control mechanisms.

Microscopic pathogens in drinking water pose a risk to public health. In Australia, chlorine or chloramine are used to inactivate these pathogens, to disinfect drinking water and prevent widespread outbreaks of debilitating illness in large populations. Although largely successful, problems arise when drinking water is contaminated by pathogens after being disinfected in the treatment plant but before reaching the customer. A variety of situations cause this, one being small pipe leaks which become a route for soil micro-organisms to get into drinking water. To prevent pathogen contamination in pipe networks, higher levels of disinfectants can be added at the treatment plant, or secondary disinfection can be administered in the pipe network. This research project produced a guidance manual which explains how to maintain and monitor effective disinfection levels in post-treatment pipelines, and the major challenges to maintaining effective disinfection.

Chlorine removes harmful pathogens from water but has the disadvantage of forming disinfection by-products (DBPs) by reacting with organic matter sometimes found in water. Chloramine also disinfects, is less likely to form DBPs and is more stable, so remains active in for longer in the pipelines which distribute drinking water from the plant to the tap. The problem is that it is difficult to predict exactly how much chloramine to add; it needs to be enough to maintain disinfecting activity in the pipeline distribution system, but not so much that customers find the smell of chlorine in tap water unpleasant. Traditionally, the chemical reaction rate has been used to predict the gradual ‘decay’ of chloramine in pipelines, but this is inaccurate. This research developed a computer software statistical programme that uses ‘artificial neural network’ concepts and operations to predict the longevity of chloramine residuals in water distribution systems. This is more accurate than traditional methods.

Some remote and regional areas of Australia rely on groundwater. A problem with this is that naturally occurring salts, such as calcium carbonate, make the water ‘hard’ and cause scale deposition on the elements used to heat water. Scale also blocks taps and showerheads. This research examined different methods for predicting the amount of scale that a groundwater might form and also considered the pro’s and con’s of various treatment technologies which prevent scale formation. The consideration of community size and the chemical characteristics of different groundwaters was incorporated into this assessment and recommendation for scale prevention.

This project developed analytical methods sensitive enough to detect the very low levels of compounds that leach out of old coal tar enamel-lined pipes, then catalogued the chemicals and the levels they were found at in a problematic pipeline. One of the chemicals leaching out of the old lining is probably acted on by microbes to produce another substance with an earthy, musty flavour. None of these were toxic in tests and they are therefore unlikely to pose a risk to human health.