Water: what comes down should go around and around

Australian cities are getting near the end of the amount of drinking water they can economically harvest without having serious impact on the natural environment. Nowhere has this been brought home more forcibly than Canberra following the impact of the bushfires on Canberra’s water catchments and its poor recent rainfall.

The situation is similar in most other capitals. New South Wales has said no more dams, and is de-rating some storages to provide more water for the environment. The annual average catchment to Perth’s reservoirs has halved since 1974. Although 130 000 households have their own domestic bores for cheap garden watering, the city has just realized that its major groundwater resource, the Gnangara Mound, is running low. Adelaide now pumps up to 85% of its water over the Mount Lofty Ranges from the River Murray. Victoria is in its eighth year of drought and many towns including Melbourne are on water restrictions.

Published figures across Australia’s 22 largest cities show that 34 per cent of domestic water is used in our gardens, and another 20 per cent is used to flush toilets. Even assuming we need that much water for gardening and toilets (and we could certainly use less), we don’t need to use drinking water for these purposes.

Australia treats nearly 2 000 gigalitres (GL) of household and industrial wastewater each year, but only about 10 per cent of it is used again for another purpose. (A gigalitre is the volume of 500 Olympic swimming pools.) The remaining 90 per cent finishes up in oceans, rivers and estuaries or is lost by evaporation. The position is worse in the cities, where in 2001-2, Sydney and Melbourne reused only 2 per cent of their wastewater Perth managed 3 per cent, Brisbane 6 per cent and Adelaide 11 per cent. What reuse there was mainly went to irrigating new crops, parks and ovals, and little of that actually saved drinking water.

The National Water Initiative, which aims to encourage water conservation in our cities, including better use of stormwater and recycled water, recognises we can do better. A number of projects have already shown the way. Bluescope Steel at Wollongong will shortly replace the 20 Megalitres (ML) a day of water that would otherwise go into the drinking water system with a similar volume of recycled water from the Sydney Water’s Wollongong Tertiary Treatment and Effluent Reuse plant. In Brisbane, the Amoco-BP refinery is taking up to 13 ML of recycled water daily from the nearby Luggage Point Plant, saving the cost of a new pipeline from the Brisbane Water supply, as well as saving the drinking water that would otherwise have been used. At Orange, NSW, all the city’s wastewater, after treatment, is supplied for industrial use in a gold mine. In Adelaide, up to 15 GL annually of recycled water is now growing commercial vegetables on the Northern Adelaide Plains. But all these projects amount to only a small amount of the recycling that could be done and savings made.

Rouse Hill in suburban Sydney is the first major subdivision in Australia with dual reticulation. Drinking water is used in the kitchen and bathroom, while recycled water from separate purple pipes is available in the toilet and garden. Approval has recently been given to use the recycled water in laundries. Other similar subdivisions are being built at Aurora in Melbourne and Mawson Lakes in Adelaide. The latter incorporates harvested stormwater.

Building Rouse Hill has been a learning experience. More than 50 cross-connections were found and corrected before the recycled water could be introduced. The recycled water, priced at 28 cents per kilolitre, has been so attractive to consumers compared with 98 cents per kilolitre for drinking water that they have used more water in total that people living in conventional subdivisions. That hasn’t been a problem at Sydney’s other dual-supply subdivision, Newington, adjacent to Olympic Park, where the recycled price has been 83 cents per kilolitre.

Price is an important issue. By world standards, the price of our drinking water is very low – one third of that of Europe. Are we properly costing drinking water and the impacts of harvesting it from the environment and of poorly treated wastewater being returned to it? Who should pay for recycling wastewater – those generating it or those wanting to use the recycled water?

Many small towns across Australia have shown how treated wastewater can be used to irrigate public parks and gardens, but it isn’t done much in our big cities. Compact recycling plants have been developed to treat wastewater withdrawn from sewers to high quality for amenity irrigation. Such a plant is being installed at Flemington Racecourse in Melbourne. One has been running in Canberra at Southwell Park for years. Canberra is moving to using recycled water in parks north of the city, and later to Belconnen, though the capital costs are significant. But if there were clear legal title available for treated wastewater, it might be better to sell the recycled water to down-stream users.

House design can also be important. NSW is introducing BASIX, a Building Sustainability Index, for new residential design. From July 2004, in stages, housing in NSW will be required to be designed and built to use 40 per cent less mains supply water than average housing of the same type. BASIX will be the mechanism for achieving these targets. Collecting rainwater is part of the equation.

It is possible to recycle wastewater on-site, though care has to be taken to ensure quality control of the processes. ACTEW installed experimental self-contained plants in six Canberra houses in 1994-5. They are still in use, though the costs of testing are high. Putting self-contained wastewater recycling units in large high-rise apartment and office buildings in the major cities may be more realistic – cities such as Tokyo and Los Angeles have been doing it routinely for years. Canberra’s Parliament House would be a good candidate.

Canberra, Melbourne and Perth have established 20 per cent recycling targets by about 2012. We need to develop new pilot recycling projects to get more experience. The bottom line is that quality control of recycled water is crucial. There must be no risk of threats to human health. Although it is even technically possible to safely recycle water back to the drinking water supply, we do not need to, and the community isn’t ready to accept it. However, Singapore already does it.

Everyone has a role in making better use of our water resources. Recycling has a role to play. To gain acceptance, water strategies should not be imposed. The community must recognise the need for change and make the decisions that have to be made.