New Technologies to Double On-Farm Diffuse Pollution Mitigation

Joint MBIE Endeavour Proposal. Successful 2018.

Project update (June 2019)

This collaborative MBIE Endeavour research programme is developing new technologies to double the effectiveness of on-farm diffuse pollution mitigation to reduce agricultural nutrient losses and associated degradation of fresh waters and estuaries.

Enhanced bioreactors and filamentous algal scrubbers will be co-developed with Māori, industry and government partners to reduce diffuse pollution from agricultural drainage and to recover nutrients. These Interceptors will be essential tools for land managers to meet impending NPS-FM limits and protect mahinga kai in accordance with Māori principles of kaitiakitanga.

The effectiveness of current mitigation technologies is constrained by: 1) episodic high drainage flows and nutrient loads, which overwhelm treatment capacity; 2) low nutrient removal of wetland and woodchip bioreactor media under peak loads, and; 3) large land area requirements and costs.

We aim to co-develop a range of Interceptors to remove diffuse pollution from agricultural drainage that will be at least twice as effective as current methods. Research to deliver this will include:

  • Enhancing nutrient removal by activating biomedia surface properties through:
    • amine grafting to provide transient adsorption of nitrate loads during high-flow events allowing subsequent denitrification;
    • forming iron/carbon nano-composites to adsorb phosphorus;
    • controlling redox to promote concurrent denitrification and phosphorus retention.
  • Enhancing denitrification rates to match nitrate loads during high-flow events by controlled organic carbon dosing.
  • Augmenting assimilation by filamentous algae nutrient scrubbers with activated biomedia for removal and recovery of nutrients.
  • Incorporating Mātauranga Māori to foster holistic resilience, sustainability and cultural acceptability.
  • Assessing effects on greenhouse gas emissions and downstream ecology including mahinga kai.
  • Quantifying and demonstrating practical performance to gain industry endorsement and meet regulatory requirements.
  • Incorporating information within farm- and catchment-scale economic and nutrient assessment models.
  • Developing end-user tools and guidelines disseminated through workshops and field-days to stimulate uptake.

Project Details

Te Waiora Research team:

  • NIWA (Chris Tanner, Rupert Craggs)
  • University of Waikato (Louis Schipper, Adam Hartland)


  • Lincoln Agritech (Aldrin Rivas)
  • Aqualinc Research Ltd (Greg Barkle)

Iwi co-development and implementation:

  • Ngati Hauā
  • Hauraki

Agricultural industry endusers / implementation:

  • DairyNZ (David Burger)
  • Beef and Lamb
  • Waikato Regional Council


  • MBIE Endeavour Fund - Successful 2018.


To develop new, highly effective bioreactors and scrubbers (Interceptors) for land managers to:

  • Reduce diffuse nutrient losses to waterways and thereby improve the health of streams, rivers, lakes and estuaries; and
  • Ensure farming can be sustainable and economically viable within the new reality of “farming within limits”.


Year 1 of 5-year project.


Rupert Craggs
[email protected]