Shutdown at Gunnamatta

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THE quality of water being discharged through the sewage outfall at Gunnamatta will drop this week while Melbourne Water works on its latest treatment equipment.

The 350 million litres a day discharge will be Class C, below the purity that has been pumped into the ocean since new processes came on line in July.

“A three- to four-day shutdown of the new advanced tertiary treatment stage at ETP [Eastern Treatment Plant, near Carrum] is required in November to undertake important works on site,” general manager of asset planning Paul Pretto said.

He said the plant’s $418 million upgrade was “nearing completion”.

“The upgrade will add an advanced tertiary stage to the sewage treatment process at ETP; the plant, originally built in 1975, will be transformed into one of the most sophisticated large-scale sewage treatment facilities in the world.”

Environmentalists who have battled for decades for the outfall discharge to be cleaned up, will now focus on ending the outfall altogether. They say the discharge of treated water into the sea at a national park is harmful to the marine environment.

Meanwhile, lower quality water from other peninsula sewage treatment plants will continue to be discharged at Gunnamatta.

“South East Water is also undertaking tertiary upgrades to its treatment plants at Mt Martha, Boneo and Somers, which discharge to Bass Strait via the same pipeline as ETP. The upgrades are expected to be completed in the second half of 2013,” Dr Pretto said.

Commissioning of the advanced treatment stage began in July “and has resulted in a progressive improvement in the quality of water supplied to recycled water customers and water discharged at the plant’s outfall at Boags Rocks [near Gunnamatta]”.

“This has had a visible and positive impact on the marine environment at the outfall at Boags Rocks. Noticeable benefits include less colour, foam, and better water clarity.

“We expect to meet our environmental targets by the end of the year and begin supplying Class A standard recycled water in 2013.”

Drr Pretto said the planned shutdown would have no impact on the supply of Class C recycl­ed water “however customers and observers at the Boags Rocks outfall may notice a temporary change in water quality back to conditions as they were before commissioning of ETP tertiary upgrade project began in July this year”.

Melbourne Water will continue to meet its EPA licence requirements throughout the shutdown, and is keeping EPA Victoria informed.

The upgrade will add an advanced tertiary stage to the sewage treatment process.

It is providing significant environmental benefits by improving the quality of the plant’s discharge at Boags Rocks on the Mornington Peninsula and increasing the standard of recycled water produced at the plant, Dr Pretto said

Once completed, the plant will treat more than 100 billion litres of wastewater to Class A recycled water standard each year.

Major construction works to build the new ad­vanced tertiary treatment stage began in early 2010 and were completed midyear.

The plant is expected to be fully operational later this year with Class A recycled water available progressively down the South East Outfall pipeline from mid-2013.

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