Mangere Wastewater Treatment Plant

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In the 1960s, earthworks for the Mangere Sewage Works sludge ponds in the lagoon damaged the landscape including the scoria cone at the centre of the explosion crater to the immediate north, and the crater itself. The sewage works handled Auckland’s waste for 40 years. Its sludge ponds stood on this shore, and its oxidation ponds webbed the harbour all the way out to Puketutu Island.
The water quality of the Manukau Harbour was already being degraded by discharges from various industries, most notably the Freezing Works at Southdown. The Sewerage Works discharges inreased the level of toxins in the water; fish numbers in the harbour dropped and the shellfish became dangerous to eat. The fumes from the works devalued the surrounding areas as well.
This situation changed in the last years of the 20th century when a new system of sewerage treatment was installed, which included, amongst other improvements the removal of the various causeways which disfigured the harbour..Between 1998 and 2005, Watercare carried out the biggest environmental restoration programme to be undertaken in New Zealand. The upgrade of the Mangere plant involved:
• an intensive public consultation and consenting process
• constructing a land-based plant that uses world-leading treatment technology
• removing 500 hectares of oxidation ponds and restoring 13 kilometres of coastline.
The plant’s advanced technology means the treatment cycle takes just 13 hours. The plant no longer uses oxidation ponds to treat wastewater. New land-based technology has allowed 500 hectares of oxidation ponds to return to the Manukau Harbour and restoration of 13 kilometres of shoreline. The old secondary and tertiary treatment processes at the plant have been replaced with new technology (reactor clarifiers and ultraviolet filtration) while other areas of the plant have either been replaced or comprehensively upgraded. Much of the operation at the Mangere plant has been computer automated. The Wastewater Business Unit has also completed a three-year programme of sophisticated computer modeling of the entire network performance.
www.watercare.co.nz/about-watercare/our-services/manger...