Final stage of Mangere upgrade with new wastewater monitoring

The upgrade of one of the world’s most advanced wastewater treatment plants at Mangere reached a new milestone this month, with an Auckland Regional Council consent to discontinue traditional wastewater monitoring methods, in favour of a revolutionary technique using ultra violet radiation.

As part of the upgrade process, which includes the restoration of 14km of Manukau shoreline and the creation of seven new beaches in place of the plant’s oxidation ponds, Watercare applied to the ARC for consent to replace using bacterial indicators of public health risk with direct measures of UV treatment performance. This treatment involves disinfecting wastewater by passing UV light through the water prior to its discharge.

For around forty years bacterial indicators - enterococci and faecal coliforms - have been used to indicate the risk of illness from treated wastewater being released into recreational areas of the Manukau Harbour. The plant treats and discharges approximately 286,000 cubic metres of wastewater per day.

Indicator bacteria have traditionally been used to indicate the presence of viruses, parasites, and bacteria such as salmonella and campylobacter, which can cause gastroenteritis, respiratory illnesses, and hepatitis.

To support Mangere Treatment Plant’s application to the ARC to replace the use of bacterial indicators, an independent study was carried out at the plant by virologist Dr Gary Gromann and disinfection expert Dr Joe Jacangelo.

These international experts found that the sophisticated wastewater treatment processes now used in the upgraded plant, meant that bacterial indicators were no longer a sound way to ensure public health protection from the plant. They recommended replacing bacterial indicators with both virus and UV irradiation monitoring.

The change came into effect from 1 October 2003 and will apply for the life of the consent (which expires in 2032).

ARC councillor Ian Bradley, who chaired the hearing held to assess the Watercare application, said the change in monitoring methods is the last step in the $451m upgrade of the Mangere Treatment Plant. “This is a win-win situation for the Auckland region – the quality of the Manukau Harbour

is vastly improved, the surrounding foreshore is being restored, and the newly created beaches will be open to the public from 2006,” Cr Bradley said.

“Watercare and the ARC have worked together to implement a world-class wastewater treatment and monitoring programme in order to make this restoration happen.”

Over the next two years, the UV treatment system will be intensively monitored in order to ensure its effectiveness. A report on the programme’s performance will be made public at the end of this probationary period.

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