Tapping the sewer
|Beauty from the beast: Flemington's famous roses will be grown with water mined from the sewer below.
The roses at Flemington will be magnificent for this year's Melbourne Cup, thanks to a new Australian sewer mining technology. By Sara Phillips.
Trevor Baldock is no weatherman but he will confidently tell you that, despite the drought, the famous roses at Flemington racecourse will be blooming come the Melbourne Cup. He knows this because his company will be supplying the water to help the roses grow.
Baldock is chairman of Zeolite Australia, which owns the commercial licence for the multiple water reuse (MWR) technology developed by Waste Technologies of Australia (see box).
"The Multiple Water Reuse is a process for recycling water. It involves taking water straight from the sewer and using it where it is. And processing it cost-effectively," he says.
The MWR technology is being piloted at Flemington through a grant from the Victorian Government's Smart Water fund. Half the size of a standard shipping container, the unit provides localised filtration of sewage through a novel arrangement of standard membranes, without the need for bacterial digestion.
"It is totally safe. It uses three levels of filtration. It removes bacteria and viruses and it also takes out the salts and the organics."
David Garman, executive director of WTA, says it can produce "class-A" water for $1 per kilolitre, comparable to the price of drinking water. Unlike the charge for potable supply, however, it factors in the true costs of providing that water. He says the price of drinking water doesn't factor in the capital cost of dams, loss of aquatic amenity, the true price of replacing assets, or provision for future technology advances.
"MWR reflects the true cost. There's no other way it can get onto the market," he says.
The economical price for the MWR water comes as membranes become more cost-competitive due to their increasing acceptance around the world and a rise in the cost of potable water.
"Water has gone up 20 to 50 per cent in round figures in the last 10 years," says Garman, adding for big users the price may be due to rise more soon. "I'm encouraged to see people discussing the possibility of bringing in multi-tiered water pricing."
The cost of running the technology is also relatively small. The total energy requirement for the MWR is around 20 per cent of the $1/kL price and can be provided by a generator.
"This is not sewage treatment," says Garman. "It extracts the water and contaminants are left to be treated most cost-effectively at the sewage treatment plant."
The technology was developed in conjunction with Memtech, now operating as Memcor, a division of Veolia Water. During trials, the device was run literally to destruction to investigate how and where failures occurred. The research team found that a minimum flow in the sewer was needed for the MWR to operate efficiently, advising that it should drill only into sewer mains to ensure sufficient flow.
The device is designed so it does not entirely drain the sewer, which would lead to problems within the sewerage system. Instead it draws an amount of water that allows a minimum flow to continue.
"One of the attractions," says Baldock, "is you can have any number of plants operating from the same sewer. If there is a series of high rise buildings, all the way along the sewer you can have a series of plants".
Ultimately he would like to see multiple MWRs drawing water from the sewer all the way to the treatment plant, where the sewage would be treated and then reused.
Baldock sees a great future for Zeolite and the MWR. He says the company is holding talks with contractors for four major Melbourne building projects, plus other property developers and irrigators about potential uses. At this early stage, it's mostly about education.
Down the track he can see industry applications in which a factory extracts water from the sewer using MWR, and then cycles its own wastewater stream back through the unit to reuse it again. Farmers may even turn to it in times of drought or if the price of river water is eventually raised.
More information at www.zeolite.com.au