Sewage flowing past desal plant

THE current off Sydney's $1.9 billion desalination plant takes sewage from an outflow only 2.5km away past its intake about a third of the time.

THE current off Sydney's $1.9 billion desalination plant takes sewage from an outflow only 2.5km away directly past its intake about a third of the time.

The environmental study used to justify the Kurnell plant's location relied in part on an assumption that because the prevailing current runs south, there would be little danger of E.coli from the sewage being sucked into its inflow, to the north.

But CSIRO scientists who monitor the current yesterday told The Australian that it sweeps north about a third of the time, and yesterday was one such day.

It has been established that on some days, the amount of E.coli in intake water is more than double the guidelines for safe bathing.

The current has been flowing north for the past week. The east Australian current, which normally carries sewage from the Cronulla near-shore outfall, is currently involved in a cold-core eddy that has reversed its direction, CSIRO oceanographer David Griffin said yesterday.

Dr Griffin said cold-core eddies occurred on a cycle of about 90 days, reversing the EAC for about a week each time. "Whenever a cold-core eddy displaces the east Australian current, the normal southward flow is interrupted. That's something that no one would argue with," he said.

Data managed by the NSW Department of Environment, Climate Change and Water also confirms the current flows north about 30 per cent of the time.

But Sydney Water's environmental project manager, Susan Trousdale, said data showed the current flowed southwards "well over 80 per cent of the time".

As reported yesterday, professor of infectious diseases and microbiology at the Australian National University, Peter Collignon, has claimed poor water quality at the Kurnell plant could create a public health disaster if filtering systems were ever to fail.

Sydney Water managing director Kerry Schott responded that seawater collected by the plant's intake was of extremely high quality. She said E.coli levels in the water were typically well below those in most dams.

However, Ms Schott's claims are contradicted by her organisation's most recent quarterly drinking water report. The report showed that of 53 samples collected between 1 July and 30 September, the maximum number of E.coli organisms per 100ml of unprocessed water was 390, with a minimum 1 and an average of 22. The annual average was 16.

By comparison, the quarterly maximum, minimum and average number of organisms per unit sample of water from Sydney's large reservoir, the Warragamba dam, were all less than 1 -- effectively zero due to detection limits. The annual average was 7.

The Australian and New Zealand Guidelines for Fresh and Marine Water Quality, published by the Natural Resources Management Ministerial Council, say the median number of faecal coliforms (such as E.coli) should not exceed 150 organisms per 100ml for safe bathing.