In March, IPENZ Auckland Branch organised a site visit to Watercare’s new Biological Nutrient Removal (BNR) unit construction site and a briefing from a Watercare representative. The new unit is a secondary process that increases the ability of the Mangere Wastewater Treatment Plant to treat flow from an additional population of 250,000.

The new BNR facility uses the same technology currently employed at the Mangere plant to remove nitrogen and phosphorus from the wastewater stream, common sources of which include farm run-off, industrial discharges, stormwater run-off, and human and animal waste. Their presence in waterways can lower oxygen levels, in turn reducing water quality and environmental diversity, and harming marine life.

The new facility, combined with planned upgrades elsewhere in the network, will allow wastewater streams currently treated at Mangere to be diverted to Rosedale, and will ensure Watercare continues to meet the expected demand for its services in an environmentally sustainable fashion.

Earthworks and foundation works are currently underway and it is expected that the operational handover of the unit to Watercare will be somewhere mid-2018.

The following photo shows the footprint of the BNR reactor.