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Content archived on 2023-01-02

SOIL CLEANING BY WET OXYDATION USING HIGH OXYGEN PRESSURE AND BIOLOGICAL TREATMENT

Objective

The treatment of contaminated soil starts with separating the coarse and fine fractions. The coarse fraction is submitted to soil washing, heavy metals being removed by extraction from the wastewater.

The fine fraction is mixed with lime and suspended in water. The suspension is led through a pipe autoclave of 3 to 5 km length where wet oxidation takes place, breaking down organic compounds into carbon dioxide or acetic acid. It was even shown that heavy metals could be bound in the lime matrix. After filtering, the process water is fianlly treated in a biological activated-sludge plant and discharged into the sewer. The cleaned soil is washed and can be used as filling material.

Advantages of the technology that was tested at the Risoe facilities are that it is applicable to cleaning soil contaminated with both organic substances and heavy metals, posing no problems with dioxins from chlorinated organics and working without emissions of volatile organic or inorganic substances; even clay soil and humus-containing, i.e. virtually non-biodegradable soil, may be successfully treated. Energy consumption is low, as compared with incineration.

On the proposal of 14-11-89, the Commission decided to assist the project at 12 % of the project costs, because of its outstanding innovatory character, environmental benefit, commercial prospects, and demonstration value. The Commission dispatched the contract to NKT on 12-9-90. Contract signature being delayed because of legislative and commercial problems in Denmark, the Commission urged and got a signed contract by 31-5-91, NKT's intention having been modified towards building a demonstration plant in Germany. An interim report was furnished on 9-3-92; Dr Ulrici visited the project on 16-12-91.

On recommendation by Umweltschutz Nord, Bremen, NKT contacted the city of Herten, near Dortmund; first tests on the contaminated soil were passed with excellent results. While waiting for further reactions from the city of Herten administration, and already trying to find, with Dr Ulrici's assistance, a German industrial partner, such as Ruhrkohle and RWE Entsorgung, for entering into the cumbersome German authorization procedures, Dr Ulrici provided them contacts with the city of Brandenburg; Brandenburg passed the contact to the Land ministry for environment protection, and there contacts were stuck.

Meanwhile, NKT had entered into modifying the construction of the wet oxidation plant into a mobile arrangement, hoping that this might facilitate the authorization procedure, only to learn that German legislation had been restrictively changed into requiring the full-fledged authorization procedure for a mobile soil treatment plant as well. Therefore, there was a further attempt made by Dr Ulrici to provide NKT a Dutch contact; this, however, did not turn out fruitful.

When NKT realized they would not be able to keep the project schedule that envisaged the termination of the ACE 89 programme by 31-12-93, because of unpredictable delays caused by the administrative decision and authorization procedures, they decided to sell their know-how to a Canadian enterprise and abandon the project in Europe.

The Commission was officially informed of NKT's withdrawal by letter of 25-5-92.

Topic(s)

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Call for proposal

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Coordinator

NKT A/S
EU contribution
No data
Address
11,Sognevej
2605 Broendby

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Total cost
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