Using MĀNUKA AND KĀNUKA for land treatment of wastewater


Introduction to The Pot project 2017

Aerial view of The Pot

                                                                                                                                 Photo credit LEI

The CIBR team at Lowe Environmental Impact (LEI), ESR, University of Canterbury and Northcott Research Associates, have obtained funds from Horowhenua District Council (HDC) and the Freshwater Improvement Fund (MfE) to carry out an exciting real world large-scale project of applying treated municipal wastewater (TMW) to mānuka and kānuka dominated ecosystems, to reduce the impacts of this land-application on the Waiwiri Stream.

“The Pot” is the local name of a 7 ha pond where wastewater from the Levin wastewater treatment plant (WWTP) is stored in, before being used for irrigation of 40 ha of exotic pines. 

The resource consent for the irrigation scheme at the Pot requires renewal and this offers the opportunity to revise the design of the irrigation scheme, with input from key stakeholders including Iwi, DOC, Regional and District Councils. The revised design has the scope to incorporate the most up to date irrigation technology, including utilising recent research discoveries on the abilities of mānuka/kānuka native ecosystems to provide enhanced treatment of wastewater.

Manuka tree

                                                                                                       Photo credit Maria Gutierrez-Gines

In this project, we will replace 10 ha of pine forest with native ecosystems comprising 40-60 % mānuka and kānuka. The mānuka/kānuka will form a contiguous mosaic interspersed with other native species that were common, or native in this area before the land was cleared. Borders of the drains and wet areas within the site will be also be planted with mānuka/kānuka and other suitable riparian species to limit contaminants entering the drain and subsequently the Waiwri Stream. Existing links with mana whenua will facilitate advice on taonga species (species of interest/treasured) that can be re-established in these areas.

This project poses a great opportunity for the researchers at CIBR for investigating the first full scale application of TMW on NZ native vegetation in the country. The applied research component of this project is twofold, first we can provide validation of the benefits of mānuka/kānuka-dominated ecosystems to enhance the land treatment of land applied wastewater in an operational environment. Secondly, we will collate information on the accumulation, fate and effects of emerging organic contaminants in wastewater applied to land. This is a knowledge gap for both councils and communities and HDC have been asked to provide key stakeholders with information on the impacts of emerging organic contaminants in the environment. 

New knowledge obtained from this project on the effects of native plant systems to mitigate emerging organic contaminants and pathogens in treated human wastewater will make a significant contribution to national and international research in the field of land treatment of biowaste.