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…