Tuesday, May 15, 2007

Potable reuse for Melbourne?

Professor John Langford is the Director of the Melbourne Water Research Centre at the University of Melbourne. An article in The Australian today reports Prof Langford predicting that Melbourne may expect to institute an indirect potable water recycling scheme sometime down the track...

Water reform to suit location
The Australian
By Matthew Warren
May 15, 2007

BY the end of the next decade, Sydney could expect to have at least one desalination plant operating, while Melbourne residents would be drinking recycled sewage, a water expert predicted yesterday.

Speaking at the Future Summit, Uniwater director John Langford said the rise of recycling and desalination was an inevitable diversification of urban water supply.

"We need a diverse portfolio," Professor Langford said. "We can no longer rely on rain-fed systems, and the modelling for southeastern Australia is that it is going to get drier. Desalination and indirect potable (recycling) are the only sources that can achieve that."

Although desalination was more cost-effective in Sydney, Melbourne's geography heavily favoured the introduction of indirect recycling of sewage into dams and streams.

As a result, Professor Langford said it would be timely to begin an education and information process for the community, to ensure a smooth transition and to avoid the risk of community backlash.

"Each solution has got to be tailor-made for the city," he said.

Professor Langford said this type of major infrastructure was part of the solution, but some of the most important reforms were "quite boring", such as reforms to urban water pricing, tighter reporting and accounting and improved understanding of the ecology.


Anonymous said...

If what the professor states is true and correct and the S/E states are going to get drier how dose he explain where the extra sewage will come from?
The communities where they have been placed on restriction have shown that the sewage plant receives less in a draught as the people have become the best recyclers on the plant and they send less and less down the drain.
They have all taken up the ideas of having one or two tanks and draw their water from that source.
The desalination plant in Western Australian should be the shinning light for a country where most of the population live on the coast.
They power theirs with the wind!!!!!
It make perfect sense to follow their lead.

Stuart Khan said...

Hello Anonymous,

You have asked an excellent question and made a number of excellent points.

If our major cities are able to get to a point where we actually don’t produce any more sewage (because we conserve water and we recycle it at home), then there will be no need to recycle it from the sewage treatment plants. I think with new attitudes to water conservation and the increasing implementation of on-site greywater recycling we are heading towards that point, but there still remain millions of litres of water which can be recycled from major plants in cities like Brisbane, Sydney and Melbourne. I don’t believe that we are capable of reducing that to zero over night, thus the best use that we can make of it is to collect it, treat it to a high level by advanced treatment processes and reuse it to our best advantage.

I’m not opposed to seawater desalination. However like all potential water sources, we need to weigh up the costs and benefits to our communities and the environment. Seawater desalination is a practically infinite source of water, but it comes with significant environmental and economic costs (as do many other sources). Nonetheless, you will be pleased to know that numerous major Australian cities are including desal in their future water supplies including Perth, Sydney, Adelaide and South East Queensland. The Perth plant is indeed an excellent example of what can be achieved.

It is kind-of true that the Perth plant is powered by wind, -but not really. The Perth plant uses electricity from the main grid, which is predominantly supplied by burning fossil fuels. The fact that they built a wind farm at the same time is very good, but this energy could be equally ascribed to providing the power to any application on the grid. If it were used for treating the same volume recyclable municipal effluent, there would be additional power credits left over which could be ascribed to any other application.

As you point out, seawater desalination is really only an option that can be considered suitable for coastal cities (and even then, only those that have suitably turbulent and robust environments for the discharge of brine).

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