One tablespoon of chlorinated solvents -- used by dry cleaners and industry -- is enough to contaminate an Olympic-sized swimming pool full of drinking water. These solvents can seep into groundwater where they break down very slowly, contaminating water supplies years after pollution has stopped. Scientists began studying groundwater in the mid 1980's. By 1995 the team led by Dr. Suzanne Lesage of Environment Canada developed a new and environmentally friendly way of cleaning up such solvent spills -- a combination of vitamin B12 and titanium citrate. On this episode of Earth Tones, see a demonstration of this innovative approach to cleaning chlorinated solvents, a field application done in collaboration with URS-Dames & Moore and AIMTech.
One tablespoon is enough to contaminate an Olympic sized swimming pool full of drinking water. Chlorinated solvents are used by dry cleaners and by industry. It takes a minute amount to poison the water, and it doesn't go away on its own. Once it's in the environment, that little bit just won't quit.
Dr. Suzanne Lesage
In the absence of anything being added it can be decades, it can be centuries. At the moment, the field demonstration we are doing is on pollution we know for a fact stopped 40 years ago. And really nothing has happened naturally. And so if we did not intervene this would be there forever.
Persistent solvents seeping into our groundwater, the water that feeds wells and springs, are a big problem.
It is a big problem, but it is a problem that we don't really have statistics for in Canada. We know, for instance, that for petroleum contamination, about one out of five underground storage tanks will leak. If we apply the same logic, about one, probably, out of five dry cleaning shops could have a problem of leaking solvents into the ground.
In the mid 1980's, when groundwater was studied for the first time in Canada, Dr. Suzanne Lesage began looking for ways to clean up solvent contamination. Bacteria are often used to clean up toxic spills, but when solvent concentrations are high, they kill the bacteria. Another safe and effective way had to be found. By 1995 Dr. Lesage had developed a new way to clean up solvent spills. The treatment is made of environment friendly ingredients - vitamin B12, essential for human and animal health, and titanium citrate. It's made from citric acid, an ingredient found in lemon juice, and titanium, a non-toxic metal. A demonstration taking place at an American military facility, the Aberdeen Proving Ground, is Dr. Lesage's bid to prove that the treatment works in the field.
It works extremely well. We're quite excited about the results because to see it going from what we could do in the lab in little vials to have actually a whole field site that may be 100 yards being cleaned up is really quite amazing - because the reaction in the well takes five minutes, which is quite amazing in environmental chemistry.
The incredibly fast clean-up time is due to the action of vitamin B12. It's a catalyst - a substance that speeds reactions up. It helps the other ingredient in the treatment, titanium citrate, to work faster. Dr. Lesage's lab model demonstrates how the system works. The B12 treatment is mixed with contaminated water in the well, represented by the glass cylinder. While the B12 binds to, or holds, the solvent particles in place, the titanium 'bites' the chlorine molecules from their surface. A molecule of the toxic dry cleaning solvent perchlorethylene becomes a much less toxic substance, ethylene, when its chlorine molecules have been 'bitten' off by the titanium. Once the water is cleaned, it turns pink - the colour of B12.
It can lower the concentration of the chlorinated compounds in the ground in such a way that then bacteria can live. And so when the vitamin B12 is finished doing its job, the bacteria can then take over. And the other ingredients that we add in our... the other active ingredient we add is the titanium citrate. It's also a source... a food for the bacteria. So what we leave behind is actually an active bacterial population.
The presence of the bacteria, which can't survive if there's too much solvent, is a sign that the treatment has worked. Using vitamin B12 to clean up solvent-contaminated groundwater is a novel approach, but it may be just what the doctor ordered - a natural solution to unnatural problems.
Earth Tones is produced in co-operation with Environment Canada.