The Best Practicable Option

As part of the resource consent renewal process, Council investigated alternative options for the management of wastewater in the region.

This involved weighing up the benefits and dis-benefits of a range of alternatives against cultural, social, environmental, technological and economic considerations.

This included looking at alternative discharge methods such as:

• Land application options (forestry land)
• Land application options (Wakapuaka farmland)
• Managed aquifer recharge options
• Potable and non-potable reuse options
• Alternative treatment facilities - Bell Island WWTP
• Tasman Bay Marine outfall

The outcome of this work was the identification of the best practicable, and affordable, solution for our community, the receiving environment (Tasman Bay) and for Nelson’s medium-term future.

The identified best practicable option (BPO) is based on the existing treatment plant technology and location. This builds on the significant investment Council have made over the years at NWWTP which includes additional pre-treatment clarifier and trickling filter, screening at both the treatment plant and upstream of the treatment plant at the Neale Park pump station (to remove grit and other materials that could potentially cause blockages), a biofilter, aerators and a cover to the trickling filter to reduce odour. Enhancements to the wetlands (that use natural processes to improve the quality of the water) and surrounding areas has been ongoing since the wetlands were established in 2010.

Assessment of Environmental Effects

An assessment of environmental effects (AEE) of the BPO was then completed and the project team are in the process of discussing the findings with the key stakeholders, such as NMDHB and DOC, nearby businesses, public groups and residents.

Te Tauihu iwi have also been invited to provide a cultural impact assessment on the BPO. This consultation process is the last step before the new resource consent is lodged. We anticipate this will be in December 2023.

Upgrading the treatment plant

Environmental monitoring is already undertaken as part of the consent. Additional monitoring of the groundwater, streams and coastal water was undertaken as part of the AEE to ensure the NWWTP is not having a significant impact on its surrounding environment.

A long-term testing programme to establish whether further pathogen (germ) removal (potentially via UV treatment) is required has also begun. A new modern diffuser at the end of the outfall pipe is planned to be installed when the outfall pipe is renewed.