If You Build It (a Wetland), They (Pollutants) Will Stay
It's hard to read a newspaper today without bumping into a story about developers destroying wetlands to build a condominium, beach house, or some other human amenity. While wetlands may be on the wane in other areas, Alaska may gain a few if Dave Maddux has his way. Maddux, a doctoral student with the School of Agriculture and Land Resources Management at the University of Alaska Fairbanks, wants to construct wetlands to help cure village sewage problems.
Maddux envisions a slew of manmade swamps all over Alaska. These constructed wetlands have the potential to capture pollutants from sewage lagoons and keep them from drifting downstream to be ingested by animals and plants.
Many Bush villages have sub-par sewage treatment facilities, Maddux said. A typical sewage management system consists of a large settling pond, into which all the village waste is flushed. Solids sink to the bottom of the stinky lagoons, and then the water is periodically released onto the tundra, muskeg, or whatever happens to be downstream. Dangerously high levels of phosphorus, nitrogen, and ammonia flow with the water to wherever it goes. Fish and shellfish in the contaminated water's path get a mouthful of pollutants, and animals dining on the funky fish or clams receive a similar dose, as do humans who drink the water.
When placed in the drainage path of contaminated water, constructed wetlands can act as a filter, Maddux said. Many plants that thrive in or near the water have the ability to take up phosphorus, nitrogen, and ammonia and store it in their roots and other tissues. By locking up the excess nutrients, the plants may be able to convert sewage runoff to water that's safe to drink.
How do you build a wetland? Maddux uses a group of six native Alaska plants ranging from buckbean, which grows in swamps with its roots dangling underwater, to pendant grass, which needs wet soil to thrive. Maddux also uses cattail, bulrush, carex (a sedge), and bur reed. These plants strain nasty stuff from water and soil and absorb it for their own use.
The plants Maddux deems suitable for constructed wetlands in Alaska are all vigorous growers that can reproduce rapidly by sending up shoots. Low-maintenance, hardy plants are essential, Maddux said, because the villagers who eventually build their own wetlands won't have a lot of time to maintain the swampy crops.
After a wetland is built, it can't simply be drowned with sewage. Depending on the size of a constructed wetland, the runoff from the settling pond might need to flow through the wetland slowly for anywhere from five to 20 days until the plants pick up the bad stuff, Maddux said. Once a plant latches onto the contaminants, the plant can be either harvested or left there. Some plants will even help to convert the nitrogen, phosphorus, and ammonia to less harmful forms.
Critics of constructed wetlands in Alaska have told Maddux that it's too cold here, especially in northern Alaska, for wetlands to work. Maddux counters by saying tainted water could be stored in the lagoons until plants become active in spring and summer, when our long days will allow the plants to work overtime. Maddux also pointed out that although he's a pioneer in regard to using constructed wetlands for village sewage problems in Alaska, the method has been used elsewhere to treat runoff from airport runways, oil refineries, mines, paper mills, and dairy farms.
Maddux is so sold on the natural healing potential of constructed wetlands that he plans to create a wetland in his backyard. I'd follow his lead if Mother Nature hadn't already provided one for me.
