PROJECT DESCRIPTION
BACKGROUND
Hexachlorocyclohexane, commonly known as Lindane, is a pesticide that has been prohibited or restricted in most European countries due to its toxicity. Since 1950, some 280 000 tonnes of Lindane were used in Europe. The region of Aragon in Spain is home to 3 sites that have been heavily contaminated. One of them, the Bailin ravine, previously served as a landfill for Lindane-containing waste. Its improper management has resulted in ground leaching and contamination of the local aquifer. Though the landfilled waste itself had been relocated to a secure isolation cell, it has left viscous residues of Lindane that spread over surfaces and seep into fractures within rocks. Efforts to manage these residues have succeeded in removing the bulk of the substance from the contaminated site, but eliminating it completely has so far proven challenging.
OBJECTIVES
The LIFE SURFING project aimed to fully eradicate pervasive pollutants in sites contaminated by Lindane. Regional authorities in Aragon, Spain, demonstrated the benefits of combining techniques from surfactant enhanced aquifer remediation and surfactant enhanced in situ chemical oxidation to extract Lindane residues from even the smallest fractures in rocks and remove it from natural environments completely. Project partners tested the combined technique in the Bailin ravine in Aragon. Better tools for decontaminating the aquifer supported the EU Water Framework Directive and Regulation No 850/2004 on persistent organic pollutants. Site measurements also shed light on the technical, economic and environmental feasibility of the combined approach, and its benefits for public health and the environment. Results helped define a strategy to replicate the decontamination process along the Gallego river and ultimately expanded it to contaminated sites affected by other kinds of pesticides and pollutants.
RESULTS
The project has successfully validated the applicability of two innovative techniques for the large-scale decontamination of soils containing residual Dense Non-Aqueous Phase Liquid (DNAPL) with a high pollutant load of multicomponent organic contaminants and Persistent Organic Pollutants (POPs).
A combination of Surfactant-Enhanced Aquifer Remediation (SEAR) and Surfactant-Enhanced In Situ Chemical Oxidation (S-ISCO) was applied in the fractured and heterogeneous aquifer of Bailín (Aragón), a contaminated site where a large part of DNAPL had already been decontaminated in the past through the pump and treat method. However, after this significant decontamination work, approximately 4% of DNAPL still remained impregnated in the rock fractures or trapped in poorly connected areas of the aquifer, prolonging the contamination of the water flow in contact with it. The project has provided a solution for efficient removal of this residual DNAPL, which cannot be removed by conventional physical means, through the combination of SEAR and S-ISCO techniques, leaving the aquifer in a much lower risk condition. During the project period, a total of 240 kg of DNAPL were removed from the Bailín aquifer, and 589 kg more in the neighbouring detrital aquifer of Sardás.
In addition, the application of the project solution facilitates the subsequent use of other final cleanup options such as microbiological treatments.
The project technique reduces treatment periods by more than 10 times, estimating a reduction of more than 50 years in the duration of the decontamination periods of surface water. It can be applied on different types of aquifers and contaminated sites, especially those affected by lindane residue contamination.
