In the site http://radixcenter.org you can find a lot of great solutions to promote ecological literacy and environmental stewardship through educational programs based around demonstrations of sustainable technologies.
The following constructed wetland was developed by Radix Center: Fantastic!
from the site http://radixcenter.org: "This system consists of several bathtubs filled with gravel, which have water plants growing inside them. Wastewater passing through the aerobic root zones of the plants is cleaned by the bacteria living there. The bacteria consume organic nutrients while the plants themselves uptake nitrogen and phosphorus. By the time it exists the system, the water has been made safe for reuse in irrigating vegetable crops. Plants used in this system include: bulrush, taro, cattail, papyrus, swamp hibiscus, canna lilly and phragmittes reeds.