Wastewater recycling uses reverse osmosis (RO) membranes to produce freshwater but this process also generates a waste stream – the reverse osmosis concentrate (ROC) – which contains almost all the contaminants present in the original wastewater. The disposal of untreated ROC poses a health and environmental risk. This research used 18 samples of ROC to test various treatment combinations and concluded that coagulation with ferric chloride followed by filtration with biological activated carbon reduced dissolved organic carbon, phosphorus and nitrogen compounds, and disinfection by-products, to safe and acceptable levels.

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.

It is prohibitively expensive and time-consuming to monitor drinking water by individually quantifying every possible polluting contaminant. Instead, living cells can be cultured in samples of the test water and if one or more toxic contaminants are present the cells die. Less toxic, more subtle effects can also be measured, for example, a toxicity test that uses cells collected (decades ago) from one monkey kidney, quantifies cell death but also measures the amount of protein made by each live monkey kidney cell. The problem with this, and other toxicity tests, is that chlorine disinfectants and harmless low levels of other substances, such as aluminium or copper, which occur naturally in water, can sometimes have inhibitory effects on the ‘bare’ cells that are often more sensitive when cultured inside laboratory culture vessels than when they were in a normal situation within a body. This research identified commonly used toxicity tests that are not affected by disinfectants or naturally occurring harmless substances, and also worked out some solutions that quench disinfectants and allow cost-effective and useful cell-based toxicity tests to be used to monitor the safety and quality of drinking water.

This paper discusses various water quality risk management techniques and proposes a step-by-step catchment risk assessment methodology that is compatible with the Australian Drinking Water Guidelines.