New Treatment System for Scheme

Tuesday, 7 April 2009

Southland District Council will use an innovative and new to New Zealand method to treat wastewaters from the new Edendale-Wyndham sewerage scheme.

Council has decided to use the BioFiltro system, which is based on vermiculture. Bacteria will break down the organic waste, and a variety of worms will feed on the bacteria to ultimately form low-volume humus, which is a soil-like residue, and a high-quality liquid for discharging, Council project manager Bevan McKenzie said.

The system is common in South America, with more than 60 plants in Chile. Plants have also been installed in France and the Chilean Air Force Base in Antarctica.

The system provides higher quality discharge and a lower construction cost than the pond-based system, originally planned for the joint scheme, 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.

Council had originally chosen a centralised pond-based treatment plant for both Edendale and Wyndham at a site between the two towns. However, it was approached by BioFiltro (NZ) Ltd and asked to consider its alternative system.

The system treats the raw sewage by first putting it through a mechanical screening filter, which removes larger solid inorganic matter. The waste water is then applied to a packed bed of plastic, screens, sawdust, rocks and bacteria. The worms within the sawdust bed provide aeration and consume the bacterial to create humus. The remaining clear liquid is treated by a UV unit before being discharged.

Investigations were carried out into the system by Council, and these showed the Biofiltro system could meet the consent conditions, including the lower level of phosphorus required by the Environment Court decision last year.

"BioFiltro has also committed to the high performance levels by agreeing to a warranty over a minimum of 18 months."

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Comments

  • Hi. What a great system to assist both the community and the environment. I would very much like to know more about this please?

    Posted by Phil Battersby, 30/03/2010 3:56pm (5 months ago)

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Southland District Council
P.O. Box 903
Invercargill 9840
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Fax: 0800 732 329
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