In recent years, Copenhagen has worked hard doubling the size of its metro network. During the construction of a new station, the ground water was found to be contaminated with chlorinated hydrocarbons. This meant that the sludge released when drilling the foundations for the concrete pillars could not be discharged via the existing settlement lagoons, which threatened the continuity of the work.

Rapid action was therefore required. That is why Logisticon Rental was asked whether it could deliver a full-scale treatment rental plant within three weeks. 

In this period Logisticon carried out various flocculation tests to separate the sludge from the water, to treat the water and to dewater the sludge. Based on the test results, a treatment installation was designed , delivered and operational within the allotted time.

The solution is based on traditional technology whereby the sludge is separated from the water by coagulation and flocculation, followed by settlement in a lamella separator. The water is then treated with sand filtration, stripping towers and active carbon filtration. The sludge is dewatered using dewatering tubes made from a special membrane that is permeable to water but forms a barrier to sludge particles. The installation has been operational for a year to the complete satisfaction of the customer.

Installation properties:

• Capacity: 15 m³/hour;
• Sludge concentration incoming water: ± 2%;
• Contamination: vinyl chloride and tetrachloroethylene (PERC);
• Discharge norm vinyl chloride: < 1µg/l.