Science and Technology for Canadians

Streaming Video - High resolution | Low resolution | RealPlayer Help

Summary

Here is a made in Canada problem, with a made in Canada solution. Natural Resources Canada scientists were called in after several cities complained about winter run-off from their local airports. The fluid to take ice off a plane's wings, ethylene glycol, was ending up in lakes and streams, and researchers found the way to get the bugs out of the de-icing system was to put a special bug back in.

NRCan scientists were able to select a bacteria, Pseudomonis putida, that degrades ethylene glycol very efficiently and with no toxic residues or by-products.

Transcript of Video

Jill Deacon
Here's a made in Canada problem, with a made in Canada solution. Federal scientists were called in after several cities complained about winter run-off from their local airports. The fluid used to take ice off a plane's wings was ending up in lakes and streams, and researchers found the way to get the bugs out of the de-icing system was to put a special bug back in.

Jay Ingram
It's the cold, hard truth about flying in winter. A fine layer of snow or ice sticking to a plane can be deadly. It disrupts air flow over the wings, decreasing lift, with often tragic results. Whether a plane is large or small, this is a common sight at Canadian airports in winter. Airports use de-icing fluid by the truckload; Pearson airport in Toronto uses nearly four-million litres a season. De-icing was designed to keep planes free of snow buildup. One of the active ingredients, ethylene glycol, actually lowers the freezing point of the snow and ice, and that allows it to melt, and then drain away. Ethylene glycol is an organic compound... it's made from natural gas... and is actually a form of alcohol... but it turns out that an ethylene glycol solution is actually NO SOLUTION if it gets in nearby waterways.

Dr. Doug Gould
Ethylene glycol is relatively non-toxic to humans... compared to many other contaminants. But when it enters the environment, bacteria will feed upon it, and use it as a food source. And in so doing, they consume oxygen, and that deprives other aquatic organisms... say a river, a stream or a lake... of their oxygen... and then results in death of a number of aquatic organisms.

Jay Ingram
Dr. Gould knows he couldn't take the ethylene glycol out of de-icing fluid... but he could find a way to keep it out of the waterways.

If he could collect airport run-off, he thought, he could use some those bacteria to disarm the glycol... and render it harmless to the environment.

But first, he had to identify the bugs that like to feed on ethylene glycol.

Dr. Doug Gould
We went to an environment where likely you would find bacteria that had been exposed to both of those compounds. We went to between two taxiways at the Ottawa airport and we took a few shovel-fulls of soil... and brought them back to the lab.

Jay Ingram
From there, it was a pretty lengthy process of elimination... to isolate the bacteria.

Soil samples were added to solutions with ethylene glycol provided as the only food source.

The bacteria were given several days to grow, and then transplanted again to a more concentrated solution.

Then they went into the incubator for several days.

Dr. Doug Gould
The process is designed to select for bacteria that do what you want... and if you force them to use only one food source... only bacteria that are able to do that will grow.

Jay Ingram
And so, out of approximately 100-million bacteria in a gram of soil... Dr. Gould was left with only 11. He grew lots of them, and then put them to the test.

This is called a Rotating Biological Contactor... that's actually exactly what it does. It's a scale model of a system that could be used at an airport... It's a trough, filled with roughed-surfaced, rotating discs.

Dr. Gould added his hungry bacteria to the system, and they quickly colonized the discs... Then he added the ethylene glycol, and let nature take its course.

In time, one strain of the bacterium called pseudomonis putida, survived over all the rest. Dr. Gould dubbed it a "super glycol degrader."

Dr. Doug Gould
We found that the bacteria would degrade up to 90-95 percent of the ethylene glycol, and the final products were basically bacterial biomass... which is non-toxic and can be used as a fertilizer, and the majority of the glycol ended up as CO2. So there were no toxic by-products remaining from... or envir... shall we say... the final end products are environmentally benign... and no toxic products as well.

Jay Ingram
The slimy coating is called a biofilm... it shows the system is working... as does a telltale odour.

Dr. Doug Gould
Most microbiological processes do have a fairly strong odour to them... but it goes with the territory... and you get used to it... in fact, the worse it smells, usually the better it's working!

Jay Ingram
Dr. Gould and three of his colleagues have received a patent for this system... It's the first time this kind of system has been used for airport waste... he's waiting for the right opportunity to put it to work.

Dr. Doug Gould
I think the most appropriate conditions for this system would be in smaller airports... perhaps military airports and airport in more remote locations... and some regional airports, in cities such as Halifax.

Jay Ingram
And in the end, it might make winter travel a little easier on passengers, and on the environment.

Jill Deacon
Tonight's Earth Tones was produced with the help of Natural Resources Canada.