There are concerns that recycled wastewater used for watering gardens or washing cars might be accidently ingested. The problem with this is that water for irrigation is not recycled to the same high (and expensive) standard as potable drinking water and might contain pathogens that cause diarrhoea and illness. Recycled water providers must quantify the risk that irrigation water might pose to public health, even though it is not supposed to be drunk. This research worked on the first part of this health risk quantification problem by developing a method to measure the amount of water a person might ingest while, for example, washing a car. Harmless cyanuric acid is commonly added to swimming pools and swimmers often ingest pool water. The amount of cyanuric acid measured in their urine is related to the volume of pool water they ‘drank’. Domestic users of recycled water are more likely to ingest less recycled water than swimmers, so a more sensitive ‘GCMS’ method for measuring very low levels of cyanuric acid was developed. It was shown to work after cyanuric acid was added to water, drunk by three adult volunteers, and then measured in their urine.

Recycling wastewater by using reverse osmosis (RO) and ultrafiltration appears to be associated with the formation of some groups of micropollutants but there is not much information about these processes. This research selected iodinated disinfection by-products (DBPs) and N-nitrosamines (NDMA), and benzotriazoles and benzothiazoles, which are compounds in dishwasher detergents, for further investigation. It was concluded that minimising the formation of dichloramine (a precursor molecule to NDMA formation) by reducing pH and maximising activated sludge ammonia production, reduced the formation of N-nitrosamines in RO-treated wastewater. Iodinated DBPs and benzotriazoles were detected in RO treated wastewater in this study but at lower concentrations than those thought to pose a risk to human health.

Wastewater must be treated to remove harmful pathogens and chemicals before it can be released to the environment, but the cost of proving that all pollutants have been removed is prohibitive because potentially thousands of separate chemicals would have to be measured. Another problem is that classical chemistry measurement tests are sometimes not sensitive enough to be able to detect the very low levels of chemicals which still harm animals and plants. This research developed a suite of extremely sensitive in vitro cell culture tests and an in-situ laboratory test in which mosquitofish were observed when swimming in recycled treated water. These bioassays measured the effects of mixtures of contaminants and were compared with traditional chemical measurements of separate contaminants. The in vitro cell culture, in situ mosquitofish and classical chemical analyses of selected contaminants generated equivalent results and led to the conclusion that combining multiple lines of evidence into a toolbox approach for the assessment of water quality provides data which is more informative and relevant when assessing potential impacts on the environment than traditional chemical measurements alone.

Wastewater (WW) contains harmful chemicals, including pesticides, that can disrupt normal gene function or hormone activity. The cost of measuring each separate contaminant at the frequency needed to demonstrate the safety of recycled WW is prohibitive. This research reviewed the risk assessment and regulation of chemicals in Australian water, with a focus on ‘thresholds of toxicological concern’. Laboratory techniques were developed to extract and concentrate WW contaminants into solutions suitable for analysis using both new in vitro cell culture assays and analysis in expensive, established chemical tests. WW and treated samples were collected from nine Australian water reclamation plants. The total effect of each sample (which contained a mixture of contaminants) on cell death, gene integrity and aspects of liver, hormone, nerve and immune system activity, was determined using in vitro cell culture bioassays, and compared with the classical chemical measurement of each separate contaminant. The cheaper cell-culture tests correlated well to the levels of groups of chemicals and could be used to find thresholds of toxicological concern. Both testing regimens also demonstrated that reverse osmosis is a highly effective method that removes harmful chemicals to levels much lower than those designated safe by regulatory authorities.

Components of dissolved organic matter (DOM) and dissolved organic nitrogen (DON) in source waters can react with disinfecting chlorine or chloramine to form nitrogenous disinfection byproducts (n-DBPs) which might be toxic and hazardous to health. In this research, water samples were collected from nine water treatment plants and found to contain 28 n-DBPs. Total n-DBP formation, and particularly brominated n-DBP formation, was affected more by the levels of bromine in raw water than the different forms of nitrogen, and this led to the recommendation that it could be beneficial to monitor raw waters with high bromine concentrations. Although chloramination caused formation of more n-DBPs than chlorination, coagulation treatment decreased total DBP levels. Further research was recommended to characterise the toxicity of n-DBPs and to optimise the removal of DOM, DON and other n-DBP precursors by using GAC Acticarb in the treatment train.

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.

Water is disinfected to remove harmful microbes and pathogens such as cholera and typhoid. The problem is that disinfection of certain types of waters, such as those containing naturally high levels of bromide or iodide, can cause the formation of disinfection by-products (DBPs). Some DBPs have been linked to cancer although this association is relatively weak because many other factors have a much stronger influence on the development of cancer than drinking water. Nevertheless, the water industry aspires to minimise this risk and conducted this research to measure the levels of bromide, iodide and other substances in Australian source waters. A number of treatments with potential to remove bromide were examined, and it was found that chlorination reduced the risk posed by iodo-DPBs.

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.