According to an expert desalination plants that are built close to sewage outflows risk contaminating drinking water. An Australian National University professor of infectious diseases and microbiology Peter Collignon said that membrane technology is not fool proof when it comes to screening bugs. This comes coincidentally just after a “reporting error” by Sydney Water that showed E.coli had been found in processed drinking water at its $1.9 billion Kurnell desalination plant in Sydney's south. The plant's intake, which collects water to supply 1.5 million Sydney homes, is about 2.5km north of the Cronulla near-shore sewage outflow.
Queensland's Gold Coast desalination plant is 27km from the nearest sewage outlet, and the closest outfall to Perth's Kwinana desalination plant is 13km away. The intake for the Adelaide desalination plant is 1.4km offshore and the nearest sewage outfall is 3km away.
According to Professor Collignon constructing desalination plant so close to a sewage treatment facility would be “one of the fundamental things you wouldn’t do. With all these plants, there are usually issues with where you situate them…You want to make sure the water supply intake is relatively pristine - in other words, low numbers of chemical or microbial contaminants that might be a problem for people,” he said.
He explained that water authorities were placing too much trust in technology that was not tested adequately. He said, “The reality of these plants is they do go wrong. They close down from time to time; people push wrong switches; membranes leak.” Usually the process of reverse osmosis desalination uses delicate membranes to remove contaminants from the water supply. Experts claim that most harmful contaminants are significantly larger than a water molecule, and therefore cannot pass through the tiny pores on the membranes.
Professor Collignon has submitted a paper to the Medical Journal of Australia in which he has reviewed the sewage treatment plants using similar membranes and detected viruses after treatment at three out of seven sites on some occasions. “The final water coming out still had bugs in it…If the membranes worked perfectly well, it wouldn’t be a problem, but they have O-rings and they can have leaks at the ends or holes in the membranes that aren’t always detected,” he explained. Professor Collignon in 2008 had helped to stop plans of introduction of recycled water from sewage into a new supply system in southeast Queensland.
A spokesman for Sydney Water however defended saying that pilot studies were conducted over 18 months before the plant was approved. The desalination plants worth 1.9 billion dollars was backed up by NSW Premier Kristina Keneally. She added, “I can't put it any plainer than this - the drinking water from the desalination plant is safe. Indeed we get it in our house, we drink it, my children drink it, I have no qualms about it.”
The NSW opposition has called for an independent contamination review of both inputs and outputs from the Kurnell Desalination Plant. NSW Shadow Minister for Natural Resource Management Katrina Hodgkinson said, “The Keneally Labor government has an appalling track record, and to now simply come out and say ‘I’m sorry about this, it’s all okay and must have been human error’ is just not acceptable and from this Government, not really believable…Most appalling is the admission that they haven’t even been testing the seawater inputs and desalinated outputs from the desalination plant for Cryptosporidium or Giardia, because they claim these pathogens cannot survive in seawater.”
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