MINNEAPOLIS - This is the bio-box, a passive filter that takes out bacteria like e-coli and others from the water. It also can remove phosphorus which can contribute to excessive algae growth in our lakes and streams. This is a small field trial that has already been going on for a year and so far the results are positive.

"So we need a 99.9 percent reduction and this media is giving us that," said Ed Matthiesen, Shingle Creek Engineer.

Here is how it works, water comes it to the bio-box through these tubes and is filtered by the sand you see below.

"It's really a sand media so imagine getting some sand, and then getting some rusty iron that are in really small particles and mixing that in. Then imagine getting some charcoal like you use for a grill and breaking that down so its a little bigger than sand size and then mixing that in. That's really what we've got here," said Ed.

After filtration, the water goes back into the stream from a pipe below. The goal is to build this on a large scale so more water can be filtered before it gets further downstream into the Mississippi River.

"Sand is cheap, rusty iron is pretty cheap, biochar we buy it by the cubic yard, its like charcoal, it's all inexpensive," said Ed.

The only maintenance required now is a once a month cleaning of the box.