Breakthrough 'anzac' Technology Can Clean Up Organochlorine Contaminated Sites And Waste Pesticides

Environment Minister Simon Upton today announced details of successful New Zealand pilot studies of a groundbreaking new technology that can destroy persistent organochlorine chemicals such as dioxins in contaminated sites.

Using a technique known as thermal desorption, the technology was jointly developed by ADI Limited, an Australian technology developer and ESR Ltd, with trials held at the Gracefield campus near Wellington.

Mr Upton said use of this technology to treat organochlorines represented a 'world first' and was an excellent illustration of what might be called
'ANZAC technology'.

"Only two years ago, what I am outlining today had not been contemplated anywhere in the world.

"We are confident that we are now in a position to begin serious planning for the clean up of sites contaminated with these long-lasting toxic chemicals," Mr Upton said.

According to the Minister, the 'hardware' or machinery involved in the thermal desorption process was not new, but the application of it to destroy organochlorines was.

"Mechanically, it is a relatively simple process which involves indirectly heating the contaminated material - such as soil- in an enclosed chamber with lime and then cracking apart the toxic molecules," he said.

"All gaseous emissions from the process are washed and filtered. Particulate material caused by the movement of gases is captured and recycled back through the process.

"All that remains of the organic contaminants at the end is calcium salt, carbon and water. The treated soil is sterile and safe to return to the site."

Mr Upton explained that the first phase of the study was commissioned in April 1995 by the collaborating sponsors - Fletcher Challenge Forests, Carter Holt Harvey Timber Group, Forestry Corporation of New Zealand and the Ministry for the Environment.

By the end of that year, the effectiveness of the process was confirmed at a laboratory scale. This verification suggested operating conditions and additives necessary to remediate soils contaminated with PCP and dioxins.

As a result of those initial encouraging results, trials were recommended to demonstrate the technology and to develop further confidence in the process at a pilot scale.

The second study phase consisted of a series of four trials involving combinations of PCPs, dioxins, and organochlorine pesticides in soils, sawdust/sand mixtures, and dust. An important technical aspect of this phase was to achieve residual concentrations in the soil better than or consistent with clean up criteria adopted for residential land use in New Zealand.

The trials concluded that:

A range of soils contaminated with various levels of PCP, dioxins and organochlorine based pesticides can be effectively treated with this technology.

The required environmental objectives of less than 50 parts per billion PCP and one part per billion dioxin in treated soils can be safely achieved.

Sawdust contaminated with PCP and dioxins when mixed with sand, can also be effectively treated.

The levels of the organochlorine pesticides DDT and lindane can be reduced to below one part per billion after treatment.

A single stage treatment technique based on recycling dusts from the process vapour streams back through the desorber could be implemented in a full scale plant.

The Minister said clean-up of contaminated sites at Mapua, at Hanmer sawmill sites, at the Southland dieldrin dumpsites, and at a number of privately owned sawmills, carried a price-tag of many millions of dollars.

"A range of issues needed to be considered in cleaning up these sites, not the least being the source of funds for clean-up.

"For a task as important as this, we need to be sure that any technology used is reliable, safe to operate, effective and that any environmental effects are acceptable to the community.

"In the meantime, I want to congratulate ADI Ltd and ESR scientists at the Gracefield campus where this work was done.

"It's heartening that a NZ Crown Research Institute has been so closely involved in the development of such leading edge and significant technology," Mr Upton concluded.