Rehabilitating gold mines

While a tonne of gold ore contains about 20 grams of gold, it can also contain more than 10 kilos of arsenic! The challenges involved in rehabilitating a gold mine are twofold: first, you have to protect humans by forbidding any direct contact with toxic products, and second, you have to protect the environment by preventing the arsenic from spreading into the ground, the air or any water.
In early 1999 ADEME was entrusted with the Salsigne site after the company running the treatment of arsenic waste had undergone compulsory liquidation. There was waste matter inside the buildings as well as out in the open. For the first six months the ADEME team developed a permanent monitoring and maintenance plan including the secured reconditioning of some of the arsenic-contaminated waste. It was also responsible for demolishing the 50 buildings on the site, most of which were heavily polluted. As for the actual rehabilitation, this is the subject of a detailed study by ADEME which will be submitted at the end of the first half of 2001.
The final phase of the project will then begin. ADEME will proceed with calls for tenders, and a storage centre will no doubt be set up on the spot for some of the arsenic-contaminated waste after it has been stabilized. There are three possibilities for the most toxic waste: it can either be sent to storage centres for ultimate waste, or stored in the mine, or recovered. The choice will depend on the acceptation criteria of the various treatment centres, and the cost.
On the strength of its experience in France, where it has already dealt with 62 contaminated sites, ADEME is developing exchanges with many other countries. In 1999 it coordinated the International Workshop on Contami-nated Sites organised under the aegis of the UN, which brought together 700 participants from 32 countries.

A paper-maker recovers sludge

By exploiting the heat-generating capacity of de-inking sludge, an industrial paper-maker produces steam and protects the environment.

In Golbey, not far from Epinal in Lorraine, the Norske Skog plant manufactures newspaper mainly from waste paper. For this Norwegian group, the world's fourth largest producer of newspaper, the principle of recycling is a priority. At the Golbey plant, which has ISO 14001 certification, all the sludge produced in the plant is recovered after mechanical dehydration, thanks to a new highly efficient boiler. And so there is no more spreading the sludge on farmland, nor recourse to a disposal site. "When we installed a second production line", explains Gilles Rouch, the Production Manager, "we knew that the amount of sludge we had to treat would increase from 60,000 to 210,000 tonnes a year. The sludge is not ultimate waste, and it is not hazardous either. It can be burnt and makes a worthwhile contribution to energy. So we hope to recover it as well as possible on the site". Thanks to a total investment of 145 million Francs (for an estimated annual saving of 42 million Francs on the operating costs) the bark from the logs in the plant, as well as the bark from sawmills in the region (which beforehand was disposed of in landfills), the de-inking sludge and that from the plant's water-treatment system are all eliminated. The steam produced by the boiler is used for drying the paper. This means a saving of 34,500 TOE/year for Norske Skog, with a return on investments over two years, and lower CO2 emissions. As for the ultimate ash, it is completely stabilized and can be used in cement works or in various road-making techniques, thus rounding off all the waste recovery.