| Dan Kotansky |
Kotansky is an environmental protection specialist at the Bureau of Land Management in Idaho.
What is the problem on this site?
At this site we had an abandoned mine that was opened in the '20s and then closed in 1946 filling up with water. It came out at the Moran Tunnel. This water would not have been a problem except that it had a very low pH and a lot of heavy metals: arsenic, cadmium, zinc, aluminum. So all these metals were impacting Champaign Creek, which is a freshwater stream holding trout down below our project area. With all the vegetation here we did not want to harm that riparian zone, so we wanted a treatment system that was passive and low maintenance and one that we could afford.
We're not treating water in the traditional sense that we're constantly adding something to it or sampling it every day. We are passively treating it with sulfate-reducing bacteria, which work under the surface and improve the quality so much that we can release it in a Champaign Creek down below.
What was the reason for choosing this passive treatment?
I think that these bacteria are working constantly. They're working all the time. They only take manure and below the surface of the water to perform and so we do not have to sample them and monitor it continuously.
Why does the water go from berm to pool?
We wanted to maximize the space here for our treatment so we have a pretty small area between the mountain and the stream. We wanted to get in as large a berm as possible. We have Pond 1 separated from Pond 2 by this berm, [which] is the heart of the treatment. It's called a "bioreactor" and the bacteria are here. We're standing on the outlet into Pond 3 and Pond 4 and so we have two berms and four ponds passively working and the bacteria working continuously to treat this water.
Is it working?
It's working right now. We would like to improve it. It's a work in progress and we'd like to get to the point where we have buffered the pH and we could really drop the metals out. Right now it's having a huge impact, probably a 50 to 90% reduction in aluminum and copper and iron. However, zinc is getting through the system, so we need some improvement on reducing our zinc problem.
Are you surprised that bacteria are cleaning up the environment?
The bacteria reduction on this water is just amazing. It's amazing what they can do for the metal problem because it's low maintenance, it's fairly inexpensive, we can haul manure ten miles, and that's just about it, once everything's working properly.
Is it self-sustaining?
The maintenance schedule hasn't been defined yet, but it will likely be between two and six years and so, no, you have to keep adding manure, you have to freshen up the populations and then it can work continuously. The beauty of it is it can work around the clock and through the whole course of the year.
Are sites like this increasing in use?
There are entire conferences and workshops now being held on bioremediation, bioreactors (which is what they're calling this berm), and abandoned mine land cleanups, and so this is what this site is all about.
Why does it take 48 hours to seep through the berm?
Forty-eight hours is a long period of time and that's the time required by the bacteria to digest and work on the metals and convert the solvate to solids.
So the water takes 48 hours to go from one pond to the other?
From Pond 1 to Pond 2. Yes. Whatever ponds that berm is separating, you want that residence time allowed for the bacteria to do their job.
Does that result in improved water?
When it gets to the creek, the water from this system is really entering it at a much improved quality than what it was before our project. One of the problems with these sites is that you have underflow from inside the fractures of that mountain taking some groundwater underneath the system and then into the creek which you, of course, cannot treat. We're trying to collect the surface water but we cannot contain all the underflow.
What is the final environmental impact?
We would like this system to improve the water quality of Champaign Creek over time so much so that we can have fish migrate upstream in this reach which hasn't been here likely since mining started in the 1880s.