Treatment plant being expanded
About 15,000 cubic metres of concrete, 80 kilometres of cables, and more than 200 workers a day.
Those are some of the figures going into a $141 million expansion of the biological nutrient removal facility at Watercare’s Mangere wastewater treatment plant.
The enlarged facility uses bacteria to remove nitrogen from the wastewater stream.
It will increase Mangere’s biological nutrient removal capacity as Auckland’s population grows by an estimated one million people over the next 30 years.
Project manager Sven Harlos is overseeing the design and construction. He says earthworks began at the site in late 2013 and the project is expected to be completed by the end of 2017.
The project includes construction of a new four-stage treatment reactor, two new 52 metre diametre clarifiers and associated pump stations, and pipes and blower facilities.
Harlos says the focus now is on installing about 80 kilometres of data and power cables.
‘‘Construction activity will taper off in September and then comm- issioning will begin. That will be followed by performance testing.’’
The increased capacity means the treatment plant can better manage large volumes of diluted wastewater caused by heavy rainfall.
Harlos says the extension will increase its biological treatment capacity from nine to 11 cubic metres per second.
‘‘It helps to protect water quality in the [Manukau] harbour and gives us much better treatment quality. The extension will be completed in about two months’ time. We’re putting in the final cables.’’
Watercare says the public is also benefitting from the project through creation of a new pathway between its popular Coastal Walkway and Greenwood Road Park.
The organisation carried out extensive planting in the area as part of coastal restoration work.
More landscaping and planting of 100,000 native plants was done to shield the facility, which is south of the existing treatment plant.
The Mangere wastewater treatment plant uses a three-step process that involves mechanical, biological and filtration and ultraviolet radiation methods to treat wastewater before it’s discharged into the Manukau Harbour.