A remediation method based on in situ* alkaline hydrolysis is tested at Groyne 42 as a part of the project NorthPestClean running from 2010 to 2013. *(in situ = on the site)

The main objective of NorthPestClean is to demonstrate in large-scale pilot experiments the effectiveness of a new remediation method based on in situ alkaline hydrolysis. Groyne 42 is heavily contaminated with the toxic pesticide parathion, which makes it a natural choice as test site.

A number of test cells will be constructed at the site. Each cell will be enclosed by a 14 m deep steel sheet piling. The test cells will be placed within the most heavily contaminated area of Groyne 42. The steel sheet piling is anchored in a thick layer of clay, whereby there is almost no contaminated water leaving or entering the cells.

Draining off the groundwater is the first step in the new remediation method. Then the contaminated soil in the test cells is infiltrated by diluted sodium hydroxide. In this way the pH in the remaining groundwater is raised to 12. The alkaline hydrolysis is allowed to take place subsurface for 3-6 months. The toxic parathion is degraded to two water-soluble and less toxic substances, which can be removed from the soil by pumping groundwater to the surface. The treatment cycle is repeated 2-3 times.

Contact-enhancement technologies are also tested at the site. The sole purpose of these techniques is to enhance the contact between reagent (sodium hydroxide) and contaminant (parathion) and thereby accelerate the process.

NorthPestClean is financed by the EU under the Life+ 2009 program, the Danish EPA and Central Region Denmark.