Turning waste into water in the City of Melbourne

More than 60 tonnes of waste have been diverted from landfill thanks to a machine installed by the City of Melbourne that turns food scraps into waste water.

Over the last year, the ORCA aerobic digestion system has used micro-organisms to transform 62 tonnes of food scraps from the busy Degraves street face precinct into greywater, making it one of the most heavily used machines of its type in Australia.

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ORCA Enviro Systems Executive General Manager Tas Papas said micro-organisms in the unit digest the waste, creating wastewater that goes straight into the sewer system via a grease arrestor.

The ORCA is basically a mechanical “stomach” that digests fruit, vegetables, grains, dairy and proteins, so you end up with greywater that is safe to put into the drain without resorting to landfill,” Mr Papas said.

“Degraves Street cafes set aside food waste as part of their daily operations. By diverting the food waste from landfill, we are also able to prevent greenhouse gases from escaping into the environment.

“Over the course of a year, that also means more than 8,000 litres in diesel fuel is saved because fewer trucks are needed on the road.”

Because space is a premium in the city centre, ORCA was chosen to handle the increased volume of food waste being generated from the busy café district.

“The ORCA has helped City of Melbourne to build strong support among local businesses for food recycling efforts and keep the bustling precinct clean and appealing,” Mr Papas said.

The machine was installed in the Degraves Street recycling Facility in May 2017. The ORCA is rolling out across Australia in pubs, shopping centres, food courts and hotels.

Population boom could lead to more recycled drinking water

Sydney’s population is set to increase by an estimated 1.74 million residents in the next 18 years which could lead to growing pains when it comes to waste water.

Dr Ian Wright, from the Western Sydney University’s School of Science and Health, said many people do not realise that Sydney already relies on recycled sewage to top up its water supplies.

“Drinking recycled sewage is a very confronting topic. But even in Australia’s biggest city – Sydney – it is an important part of the water supply,” said Dr Wright.

“The large settlements of Goulburn, Lithgow, Moss Vale, Mittagong and Bowral all discharge their treated sewage into the catchment rivers of Sydney’s Warragamba Dam,” said Dr Wright.

“There are also sewage treatment plants located in the Blue Mountains, Penrith, Wallacia and West Camden, all of which discharge their treated sewage into the Hawkesbury-Nepean River,” he said.

“The North Richmond Water Filtration Plant extracts and treats this water to supply some parts of north-western Sydney.”

Dr Wright says this method of ‘indirect potable reuse’ of treated sewage is common, and the water is highly treated to ensure it meets Australian drinking water guidelines.

He says no Australian urban water supply currently uses ‘direct potable reuse’ of treated sewage – which involves the water being transferred from a sewage treatment facility directly into a city’s water source, without it first being mixed into a dam, river or reservoir.

But if Sydney’s population grows at the rate expected, the concept will need to be seriously considered.

“Available data is limited, but in the recent dry summer I estimate that treated sewage comprised about 20% of the Hawkesbury-Nepean flow in the North Richmond area,” says Dr Wright.

“Much of Sydney’s population growth will be in western Sydney, one of the most rapidly growing urban populations in Australia. And this will result in more treated sewage, and urban runoff, contributing to the Hawkesbury-Nepean River flow.”