New sewage treatment plant to use worms

Edendale and Wyndham will soon be home to what is thought to be New Zealand's first worm-based sewage treatment system after the Southland District Council decided to use the unique technology.

The BioFiltro system uses tiger worms to break down organic waste and ultimately form low-volume humus, a soil-like residue, and a high-quality liquid for discharg-ing.

Raw sewage is first put through a mechanical screening filter, then applied to a packed bed of plastic, screens, sawdust, rocks and bacteria.

The worms then begin their work in the sawdust to provide aeration and consume the bacteria.

Project manager Bevan McKenzie said initial construction would begin in the next two to three weeks with a possible test date in late July.

The new system would provide higher-quality discharge and a lower construction cost of about $1.5 million, Mr McKenzie said.

"The BioFiltro system could save up to $1 million in construction costs and this saving would allow the scheme to be built within the original budget," he said.

The council had originally chosen the more common pond-based treatment plant for the two sites but decided to consider the alternative system after being approached by BioFiltro NZ Ltd.

The decision follows more than two years of consultation and research by the council into the BioFiltro system, including two council engineers travelling to Chile to see the technology in action.

The system was developed in Chile and is common throughout the country, which has more than 60 plants in service. It has also been installed in France and at the Chilean air force base in Antarctica.

- © Fairfax NZ News