Improving risk assessment for recycled water: domestic laundries and recreational parks

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Recent droughts in Australia have meant that recycled water is becoming increasingly important to ensure the sustainability of our water resources. There are four different classes of recycled water (Class A, B, C and D), depending on the level of microbiological contamination. The potential level of exposure of the population to recycled water determines the class of water suitable for various reuse purposes. The need to address water recycling issues in Australia has resulted in increasing numbers of innovative recycling schemes such as dual reticulation systems which supply two qualities of water to households, one of high quality for drinking and a second piped system delivering treated recycled water for non-potable (non-drinking) use. In this project, we will investigate the safety of using recycled water in different situations by using water with different known concentrations of micro-organisms to simulate recycled waters of different classes. Most state health authorities in Australia do not approve the use of recycled water for machine washing because of a lack of safety data, but its use in laundries could significantly reduce the need for high quality drinking water. We will perform experiments to help determine the safety of using recycled water for rinsing clothes during a washing machine cycle. Another use of recycled water is for irrigation of recreational parks. Because of safety concerns, when recycled water of Class B or C is used, some states advocate that the public must wait at least 4 hours after watering before they can gain access. This time period may be unnecessary. We will perform experiments to assess the potential exposure to micro-organisms in grass for park users at different time periods following irrigation with water of various classes. The information obtained from this project will help in the decision-making of health and water regulatory agencies.