Pure water wasted

The crisis of water supply to our cities is now of tragi-comic dimension.

A grandstand of politicians of all persuasions offers ever bigger engineering fixes. Proposals include massive new dams, large-scale water recycling, new pipelines and costly desalination plants.

None can be readily implemented; all are expensive; none will help cities cope with climate change; all have major environmental consequences. Each, in short, is a mirage.

The proposals all seek to maintain or increase the supply of potable (drinking quality) water. The reality is that 90 per cent of water used in households need not be of that quality.

In Australia, using potable water to flush a toilet is disturbingly wasteful. When this practice began in the 1880s there was a ready supply of potable water for the then attractive novelty of body waste disposal. Things have changed substantially since then.

Southeast Queensland now faces a crisis that exposes the flawed thinking that shaped our historical approach to urban infrastructure, especially for water and sewage.

There are, however, straightforward technological and behavioural changes that can help us out of the water shortage mess. Australian water authorities need to overcome their entrenched scepticism and resistance towards these changes.

Brisbane's demand for potable water could be greatly reduced by using dry composting toilets and or by using on-site treatment and recycling of grey water to flush toilets.

Using on-site recycling of grey water or rainwater in the laundry could significantly reduce use of potable water. Bathroom use, including showers, accounts for about a quarter of household water consumption.

Grey water from the bathroom could be treated and stored on site for use in the laundry, for toilet flushing or garden watering.

Recent attempts at changing water consumption have had limited success because they do not attack the problem in a fundamental way.

Increasing the price is one common approach to reducing consumption. This misunderstands the nature of water demand and the way it is affected by cultural and behavioural factors such as fashion in hair care and clothing. It also overestimates the public's ability and willingness to reduce basic water-using activities, such as bathing and domestic cleaning.

Moreover, a significant proportion of households live in flats that are not separately metered, so they have little idea of, or concern for, how much water they use (or how much it costs). Flat dwellers tend to believe water shortage is caused not by their consumption but by those who live in houses.

Significant water price rises also have serious equity effects. Doubling the price may have no effect on high-income households but can be onerous for low-income or larger households.

Rather than focus on "big engineering" proposals to increase supply, we should develop measures that encourage (and eventually require) households and businesses to harvest and treat much of their own water. This would require a program to capture and store rainwater for domestic consumption. All new dwellings could be required to install rainwater tanks of reasonable size to supply water for bathroom use. This would not only give households some responsibility but would also provide them with a degree of security in their own supply.

All new dwellings could be required to install greywater recycling systems that store treated water for uses that do not need potable water. An extensive program to retrofit older areas with rainwater tanks and greywater treatment and recycling systems also should be implemented.

Households would become more responsible for the quality of their own recycled grey water and would thus be encouraged to use detergents and cleaning agents that have low levels of phosphate and sodium. That would reduce the amount of these chemicals in sewage and make it easier to treat.

Ultimately, water authorities should be required to deliver a small supply of water to households as their environmental right. But this need not be more than 20 kilolitres a person a year - sufficient to meet their water needs for drinking and food preparation.

Water authorities would thus meet their original remit as suppliers of potable water. They could develop their role as health agencies responsible for sanitation services without using potable water to deliver them.

The ultimate goal is decentralised water supply and sewerage networks that would be vastly more sustainable and secure than the systems that are failing us now.