Like many other long-standing chemical companies, WACKER has some soil contamination on its premises. In the pioneering days of chemical production, nobody was aware of the dangers posed by certain chemicals, or that some substances could persist in the ground for extended periods without undergoing degradation.
To remediate this legacy of contamination, WACKER has been extracting air from the soil at the Burghausen site since 1989. This removes predominantly the highly volatile halogenated hydrocarbons from the soil, which are then incinerated to render them harmless. To date, 1,921 metric tons of chlorinated hydrocarbons (CHCs) have been removed in this way. As soil treatment progresses, the amount of contaminant removed decreases, as is to be expected. In 2010, only 23 metric tons were removed (2008: 35 metric tons).
Since 2003, we have been using a groundwater stripping plant to treat an area of localized groundwater contamination east of the Burghausen site. By the end of 2010, 25 metric tons of CHCs had been removed; pollutant concentrations have been reduced to one fifth of their original levels. In order to reduce the discharge of hexachlorobutadiene (HCBD) into the tailrace, we are continuing groundwater treatment of the site’s contaminated areas. The already very low HCBD concentrations continue to fall. Currently, 65 kg of the pollutant is being removed per year. The results of our fish contaminant survey at Burghausen indicate that HCBD discharge into water bodies is falling and that the fish are quite safe to eat.
Additionally, there is some groundwater contamination at our Nünchritz site. The solvent residues predate WACKER’s takeover of the site. We have been cleaning up the groundwater there since 2009 and in 2010 we increased the scope of our remediation efforts. We performed an in-situ field test to investigate whether pollutants (solvent residues) in the groundwater could be broken down by naturally occurring microorganisms. We expect to receive the test results in 2011.
In 2010, we decontaminated the land earmarked for the construction of Nünchritz’s new polysilicon production facility. We removed 75,000 metric tons of contaminated sludge and disposed of it correctly. This remediation work meant that we could build the new facility on the existing site rather than having to use uncontaminated land. That same year, we began to expand the Nünchritz wastewater treatment plants in preparation for the commissioning of polysilicon production at the site in 2011. In spring 2011, additional chemical-mechanical cleaning stages were incorporated into the water treatment system, doubling the capacity for inorganic wastewater.
Siltronic’s site at Portland (Oregon, USA) developed a process to biologically degrade trichloroethylene (TCE) residue in groundwater using microorganisms. As a result, TCE has decreased by 99.9+ percent in the treated areas.
Prior to 1973, chlorinated hydrocarbons were stored in a chemical warehouse in the southern part of Düsseldorf. For reasons that remain unclear, some of these substances contaminated the soil and groundwater. At the time, the warehouse was rented by a shipping company. Deutsche Bahn (Germany’s national rail company) owns the site, which is now being remediated. WACKER and the shipper are to make a contribution toward the cleanup costs.