Horne: Wetlands are a dynamo of productivity.

Narrator: This is Science Today. You see them all the time -- a bunch of reeds and grass growing in shallow water. You might call them swamps. Ecologists call them wetlands.

Horne: Increasingly nowadays, we are creating wetlands that are very purposeful.

Narrator: Ecologist Alex Horne of the University of California, Berkeley creates wetlands with a very specific purpose: sewage treatment. He says an artificial wetland can treat sewage just as well or better than a high-tech treatment plant. The reason: wetlands have countless sewage-eating bacteria and almost unlimited solar power.

Horne: Basically, the usual wetland we think about is a bunch of reeds and vegetation that's only a foot or so high, maybe a meter high, and if this is so, then all that sunlight is compressed into that short little area, there's no other way the sunlight can be used other than to heat the surface. So the plants can grow profusely, they can grow for a long time, that energy can be used directly or it can be stored in dead material and recycled very quickly.

Narrator: Horne thinks of wetlands as open-air chemical transformers -- turning sewage into inoffensive mud. For Science Today, I'm Steve Tokar.