Multidisciplinary Projects

Remediation of TOTAL acid tar lagoons in Ertvelde (Ghent, Belgium)

On its premises in Ertvelde, TOTAL Belgium has three old lagoons containing acid tar, a residual product from the former production method of white oils.

DEC was awarded the design & build contract for the remediation of the acid tar lagoons. There are not many available solutions for the treatment of acid tar and the client wanted to be certain that the proposed techniques would work.

DEC proposed a treatment technique in which the acid tar is stabilised, using CalDEC (a neutralising additive developed by DEC) and then disposed on site in an engineered cell.

An additional problem was the emission of sulphur dioxide and the accompanying odour nuisance. DEC developed an alternative excavation technique to eliminate the nuisance for all those on and near the site. Odour metres were installed around the site that immediately sound an alarm when sulphur dioxide is detected.

For the entire operation, a specific plant was constructed on the TOTAL premises. It was made completely air-tight so that harmful odours could not escape. The odours are neutralised after being collected via a vacuum system. The plant was constructed and made operational at a record speed of three months.

The premises were heavily bombarded during World War II (after the construction of the acid tar lagoons). As a result, there is a real danger of finding as yet unexploded bombs during the work. In addition to a highly advanced preliminary bomb detection, DEC also established good contacts with the civil defence organisation.

Finally, a large scale water purification system was also designed, constructed and tested for treatment of the contaminated groundwater and process water that is discharged during production.

The project consists of three stages:

• Stage A (September 2004 – March 2005): design stage with first treatment tests with CalDEC on a small scale;
• Stage B (April 2005 – December 2005): pilot stage with large scale treatment tests and construction of the plant;
• Stage C (January 2006 – 2008): execution stage: treatment of all acid tar in the lagoons.

Safety

In October 2009, DEC was awarded the IADC Safety Award for this project. Each year IADC seeks to honour one of its member companies that has shown outstanding achievement in the area of safety. The IADC Safety Award is intended to encourage the development of safety skills on the job and to reward those people and companies demonstrating special diligence in safety awareness in the performance of their profession.