Office for Environmental Programs - Theses

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An assessment of environmental risks of using recycled water to create environmental flows in the Werribee River, Victoria

Ewert, Jamie M. ( 2004)

Recycled water created from highly treated sewerage is now considered a viable water source for selected, appropriate uses. One potential use is to create environmental flows in stressed rivers if this is a low risk and low cost option. To evaluate these risks, a case study is investigated using the degraded Werribee River, Victoria. Environmental flows could be supplied to the river from the nearby Western Treatment Plant. Risks are identified using the judgement of river and water management experts and are evaluated using conceptual models and a Bayes network. Key risks investigated include risks to human health (gastroenteritis and arbovirsus infection) and risks to environmental health (blue-green algae blooms). Results show that these risks already exist to some degree but are unlikely to increase if recycled water is used to create environmental flows. While the creation of environmental flows with recycled water creates opportunities for health risks to increase, the risk is limited by low numbers of infected hosts. Blue-green algae risks are already high as the river currently exceeds nutrient guidelines. Adding more nutrients will not increase this risk and interestingly improving stream flows using saline recycled water will prevent blue-green algae accumulation, actually decreasing the risk.