by Walter Mugdan
In Part 1, I explained that a large variety of chemical solvents were concocted over the past two centuries. They are integral to nearly every industrial enterprise, but many of them are dangerous to your health if you ingest or inhale them. Among the most common is PCE or “perc,” which is a probable human carcinogen. The most common use of perc is as dry cleaning fluid. In the past, many dry cleaners simply dumped their used perc on the ground, contaminating both soil and groundwater. EPA’s “Superfund” list of the worst toxic waste sites in the country is littered with former dry cleaning facilities.
One of these Superfund sites is located in Nassau County, just a stone’s throw from where I live in Queens County. I’m in the Little Neck part of Queens; and the former Stanton Cleaners sites is a half mile away in Great Neck. When Stanton dumped its used perc down the drain, it contaminated the groundwater below. This is bad enough under any circumstances, but here it was particularly dangerous, because Stanton was only about 300 yards away from a Great Neck drinking water supply well. To make matters even worse, perc vapors from the contaminated groundwater were getting into nearby homes and a synagogue.
The Stanton site was added to the Superfund list in 1999 and EPA installed a “pump-and-treat” system. This is one of the ways that we use to solve our solvent problems. Contaminated groundwater is pumped up to a small building at the back of the dry cleaner’s parking lot. There it’s treated to strip away the perc, and returned clean to the ground. More than 200 million gallons have been treated to date at the Stanton site.
As a precaution, a treatment system was also installed at the drinking water well; and vapors are now vacuumed from the soil before they can reach homes and other buildings. (The current dry cleaning operation – a different company, though still using the Stanton name – has state-of-the-art equipment to prevent perc from entering the ground.)
Over the past three decades, we’ve developed a variety of techniques for solving solvents problems. In a “pump-and-treat” approach like the one used at Stanton, the contaminated groundwater is cleaned by passing it through a carbon filter or an air stripper (in which air is blown through tiny water droplets, stripping away the contaminants). Alternatively, various in situ techniques can be used to clean the groundwater in place. Other chemicals that react with the solvents to form harmless substances can be added to the groundwater; or nutrients can be added to stimulate microbes that degrade the solvents. Continue reading