Quick Dips

Waste in the Woods

Scientists at Rotorua and Christchurch are looking at how human waste can be spread in plantations as a means of disposal and as a way of boosting forest production.

"Forested land treatment systems for wastewater have been in New Zealand for more than 10 years," programme leader Dr Mark Torner of Forest Research says. "But there are no design or management criteria that enable these systems to be run sustainably."

"Biosolids applications are being looked at increasingly, because, as improved wastewater treatment technologies generate more sludge, options to sustainably recycle these wastes onto land rather than into water or landfills must be developed."

Tomer says plantations will probably be preferred because of environmental benefits, nutrient recycling, and less risk to public health and land amenity values.

"So it's critical that design and operation criteria for land treatment systems be developed based on a scientific understanding of the fate and effects of these waste materials in the forest ecosystem."

"Thirty-six plots, each five by five metres, have been constructed. Fifteen of these plots are filled with dune sand to allow an on-site comparison between two soils, sand and the native volcanic soil.

"The results will allow us to determine how effluent treatment and application rate affect the trees, the soils and soil leaching, so that we can make specific recommendations on designing and managing land treatment systems."

In collaboration with NIWA scientists, the team aims at seeing how effluents pass through and affect wetlands.

"This work will help determine how wetlands might best be designed and used to act as a backup system for nitrogen removal for land treatment systems."