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Arial view of the plant

Reducing greenhouse gases and improving efficiency in NZ

The Rosedale wastewater treatment plant in Auckland currently has capacity to process wastewater from a population of 240,000.

ClientWatercare Services Limited Offices
ExpertiseConcept and detailed design


It was designed to be expanded to serve a population of up to 320,000 and peak flows of up to 4m³/s. We are acting as the principal engineer for the upgrade, which includes expansion of the primary tanks, odour control equipment, modified Ludzack- Ettinger bioreactor, digester, UV disinfection and associated electrical infrastructure.


We have designed a new digester and the integration of thermal hydrolysis technology with connection to a new gas engine and flare, which adds additional sludge retention time to the anaerobic digestion process, providing more resilience. It has the added benefit of reducing greenhouse gases and improving the yield of biogas, which is used to power engines that will meet more than half the electricity needs of the plant.


More advanced technologies have been incorporated as well as a reconfiguration to futureproof the entire digestion process. We are assisting with the integration of sustainable practices which will help Watercare achieve its goal of running the plant on 100% self-generated electricity by 2025, a target that will see it reduce its electricity demand on the grid by approximately 37GWh every year.

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