Rosedale plant's energy-efficiency ranking hits top five

Our Rosedale Wastewater Treatment Plant has been named in the top five most energy-efficient plants in Australasia.

Rosedale ranks number five out of 22 in the Water Services Association of Australia’s 2017 survey of plants with activated sludge treatment and on-site co-generation.

Wastewater technology manager Paul Bickers says the top-five ranking was an outstanding outcome.

“It shows that, in terms of technology and efficient plant management, we’re comparable to large plants in Australia,” he says.

“And when it comes to energy efficiency, Rosedale has the advantage that the wastewater treatment process uses gravity to move flows around the plant, so the only pumping required is for the solids process. We also have natural UV disinfection that occurs in the ponds, so a lot of the time we can turn off the UV plant and rely on the sun instead.”

“Together with some other innovative process improvements, the thermal hydrolysis facility will move Rosedale closer to self-sufficiency,” Shane says. “Further process enhancements are on the drawing board and are currently being trialled at laboratory scale.”

Rosedale was also credited for its co-generation of power using biogas generated from the activated sludge.

“We’re currently 74 per cent self-sufficient at Rosedale by creating and using our own power,” Paul says.

Chief operations officer Shane Morgan says the benchmarking exercise serves as an effective tool to measure our plants’ performance as part of our goal to achieve energy neutrality.

“We’re aiming to reduce our energy use by eight gigawatt hours a year by the end of 2018 – and by the end of 2025, we want both our Rosedale and Mangere plants to be energy neutral.

“The survey gives us a sound baseline measure, before our programmes of work to hit our energy targets really kick off,” Shane says.

Preliminary design is under way for a new thermal hydrolysis facility at Rosedale – the first in New Zealand. This innovation will improve the quality of the biosolids and further increase the biogas and power generation for the plant.


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