piped 9km each day from the wastewater treatment plant at Moa Point, in southeast of Houghton Bay, to Carey’s Gully sludge dewatering plant at the Southern Landfill. According to the city council, once most of the water is removed, about 45 tonnes of solids are buried in the landfill per day, while the remaining water is returned to Moa Point via the wastewater network.
Therefore, local government recently announced plans for a Moa Point sludge minimisation facility, which aims to minimise sewage sludge by using modern technology, so that the amount of waste going to landfill is reduced. Currently, the island nation’s electricity mix is underpinned by coal, which continues to expand the country’s carbon footprint. Accordingly, under the recent initiative, large volumes of sewage will be reduced to a product resembling potting soil, with the use of modern technology. This is anaerobic digestion will produce a gas that will be used to generate electricity.
According to the authorities, the process will reduce sludge volumes by 82 per cent and lower carbon emissions by 63 per cent.
The project’s technical director Chris French noted that they aim to set up a system which is as self-sufficient as possible. As the thermal hydrolysis chamber is heated by the heat from the digestion tank, any excess would likely be returned to the grid to generate electricity. “We estimate that up to 500kW of electricity could be generated from the new plant, depending on how we configure the process,” he said. The waste water expert noted that the initiative creates potential for some of this heat to be transferred to event heat the airport’s terminal.
