It’s what’s in recycled water that matters
Acceptance of recycled water for residential use in the Mawson Lakes
community depends on the quality and attributes of the recycled product and
the purpose for which it will be used, a University of South Australia study
has found.
Recycled water has just started flowing through purple pipes in Mawson Lakes for toilet flushing and watering of gardens and community areas, and the views of local residents, even before the first gush of grey water came online are quite clear, according to Professor Jennifer McKay, Director of UniSA’s Centre for Comparative Water Policies and Laws, who supervised the study.
In conducting the research, PhD student Anna Hurlimann surveyed residents to gauge their attitudes to colour, odour and salt levels of recycled water when used for different purposes, and what price they thought it should cost.
Residents rated low salt levels as very important for gardens, 8 on a scale of 0 – 10, when compared with having no colour 3.8, and no odour about 5.7. For toilet flushing, salt wasn’t an issue but no odour and no colour were important, according to Hurlimann.
“Based on this study, it’s clear that the quality of recycled water needs to suit the purpose for which it is being used,” Hurlimann said.
By far the biggest volume of recycled water is used for garden watering, totalling more than 40 per cent of all water consumption.
Hurlimann believes that the quality of recycled water will be very good most of the time. Storm water is being added to the recycled water to balance the salt content, but levels could fluctuate depending on the availability of storm water for flushing, especially in summer. If there is excess biological growth, an odour may be present, but Hurlimann expects that to be a rare occurrence, although a slight colour may be evident on occasions.
In addition to the quality of recycled water, price was also an issue for residents.
“They thought that drinking water should cost $0.60/kilolitre (kL) and recycled water $0.46/kL, which is much less than what they pay at the moment. Only a small percentage, 23 per cent, thought that prices were fair,” Hurlimann said.
Prices for drinking water currently include an annual metre fee, and $0.44/kL for the first 125 kL plus a flat rate of $1.03/kL for additional water used, less discounts for certain cardholders. For recycled water residents pay a one-off metre fee on installation and a flat rate of $0.77/kL based on the amount of water used.
Because of the pricing structure, it wasn’t clear to many residents that recycled water was much cheaper than drinking water. Some residents also complained that there were no pension allowances or discounts for recycled water.
Hurlimann believes that policy changes on the pricing of both drinking and recycled water should be considered.
“The cost of recycled water needs to be restructured, with a similar stepped approach to drinking water, and perhaps we should also consider revising the pricing structure for drinking water by charging a flat rate, as is the case in other states.
“People have a negative reaction to paying high prices for recycled water because they perceive the quality to be lower and perhaps perceive there to be some risk as well. Around Australia the policy has been to discount the price of recycled water, even though it costs a lot more to produce, with extra treatment and transportation making the real cost estimate as high as $4.00/kL,” Hurlimann said.
“There needs to be a balance between encouraging use, as well as retaining its value and recovering costs. We think it’s really important to make recycled water projects economically feasible. The big issue, which we are exploring further, is the economic feasibility of recycled water projects for the long term,” Professor McKay said.
“Most treatment plants are positioned higher than their catchments, so water has to be pumped uphill to get treated, which uses a lot of energy. The Bolivar plant is ideally placed to treat water for recycling at Mawson Lakes because both are situated on the same level and are only eight kilometres apart, and Bolivar is geared to treat water to a high standard and at the required volume,” Professor McKay said.
“There are many positive environmental impacts of using recycled water at Mawson Lakes,” Hurlimann said.
The research has been funded by the Cooperative Research Centre for Water Quality, which also funded Ms Hurlimann’s scholarship; the City of Salisbury; and SA Water, a partner in the original research grant, which continues to support the research with data collection.