Building a wetland: the natural way to treat sewage

Article by Sharon Chickering

Environment – April 1996 – Colorado Central Magazine

I sat in the sunny corner window of the Mt. Elbert Lodge with owners Scott Boyd and Laura Downing, watching flighty chickadees attack the hanging bird feeder. Just beyond the line of brown willows flowed the icy water of Lake Creek. There was nothing to indicate that under the picnic table sitting just below us in the snow lay the wastewater treatment system for the bed and breakfast resort.

Downing and Boyd are among a handful of Colorado residents turning to constructed wetlands for treatment of their household waste/sewage.

Two years ago when the couple purchased the mountain property on Highway 82 four miles above Twin Lakes, they knew the Lake County Health Officer had already mandated replacement of the antiquated sewage disposal system. The sewer regularly backed up and untreated waste water was seeping directly into surface and groundwater. It wasn’t the kind of environment to which they wanted to attract guests.

Treatment alternatives included: building a mechanical wastewater treatment facility on the property (a potential eyesore in their pristine setting); installing holding tanks which would need to be pumped regularly; or constructing a wetland. In an area of abundant natural wetlands and a high water table, the constructed wetland seemed the best solution. Despite the high installation price, the system has virtually no on-going costs, unlike the other two alternatives. It also had the advantage of enhancing rather than detracting from the beautiful surroundings.

Downing and Boyd are enthusiastic about the system: “The wetland is an integral part of our place and people don’t know it’s there. . . We haven’t had any complaints about odor.” They also have nothing but good things to say about John Grove of Grove Constructed Wetlands who designed the system.

Wastewater from the six guest cabins and main lodge is now funneled into one of four septic tanks for primary treatment. Here solid material settles out. The grey water then flows into the constructed wetland, in this case an 80 foot long, 16 foot wide, 4 foot deep “swimming pool” with waterproof lining which is filled with 3 1/2 feet of gravel and topped with another 6 inches of pea gravel.

The subsurface flow system (meaning all water is below the surface) is planted with moisture-loving plants such as bulrushes, sedges, iris and roses. Grove is adamant about using native species as much as possible. He wants the area to be aesthetically pleasing and blend in with the surroundings. Once vegetation is established, people can walk on the solid surface with no hint of water being recycled just below their feet. Grove’s favorite compliment is when people don’t realize the wetland is there.

As effluent enters one end of the wetland, control structures or buffers direct the horizontal percolation so exposure time is maximized. The purpose of the wetland would be defeated if channels developed allowing water to run through quickly. As the effluent flows around and through, diverse populations of microorganisms clinging to underwater plant surfaces as well as to the gravel do the work of breaking down and absorbing wastes. Above-water plant parts help by absorbing oxygen and transporting it to lower stems and roots where the microorganisms use it for respiration.

After spending about a week in the wetland environment, the water, yellow and “yucky” when it entered, runs out clear into a traditional leach field. By the time it reaches the groundwater or nearby streams, it is well within acceptable standards.

Although skeptics predicted the wetland might freeze solid during the long, harsh winters at 9,800 feet, that has not been the case. Even the first winter, before much vegetation had been established, the wetland did its job of biologically treating the water. By insulating the septic tanks, using a stock tank heater with one, and adding heat tape to the outflow pipe, the wetland functions well throughout the year. To prove the point, Boyd dug through three feet of snow to the level control structure to show how water was trickling out of the system, even though some ice had formed on the surface.

In a natural settings, wetlands combine plants, soil, bacteria and animals to “treat” water. Originally, wetlands took care of much water pollution, but wet “waste” lands have been appropriated for other purposes at an alarming rate. Less than half of the 215 million acres of wetlands in the U. S. at the time of European settlement remained by the 1970s. Problems also multiplied as the sewage from dense population centers overwhelmed the remaining wetlands’ ability to deal with it.

Today in Colorado alone, between ten and fifteen thousand on-site sewage treatment system permits are issued every year. The use of individual constructed wetlands tends to make people more aware of potentially toxic substances like paint thinner or anti-freeze that they might be tempted to flush down the drain.

In addition, the Clean Water Act now discourages the use of natural wetlands for systematic wastewater treatment. Sewage running into these wetlands is subject to stringent point source pollution regulations. While constructed wetlands mimic these natural processes, they can be designed for maximum efficiency and are not subject to the same set of rules.

Working with the Buena Vista Sanitation District (BVSD), John Grove has designed a much larger treatment facility involving subsurface flow as well as free water surface (FWS) wetlands. While subsurface systems are best for individuals having limited amounts of land, free water surface wetlands are appropriate for entities with more acreage.

The principles of treatment are the same but the FWS is fairly shallow and the surface of the water exposed — more like a traditional marsh or swamp. Because these wetlands cover larger areas, they are apt to attract greater wildlife populations (birds, frogs, deer, etc.) and can also provide recreation opportunities.

If phased-in as Grove envisions, these BVSD wetlands would replace the present water treatment lagoons which are no longer adequate for the needs of the growing district. One of the major selling points is that the up-front capital costs would be 40% less than those of a more traditional system. Dependence on plant and animal growth rather than more expensive chemicals and energy would provide further savings in routine operating costs.

While mechanical systems last twenty to twenty-five years, Grove estimates a constructed wetland system could have a life-span of one hundred years (although no one really knows because none have been in existence that long).

“In this country we don’t see waste as anything but waste,” he says. “Other countries see it as a resource.”

Laura Downing certainly sees it as a resource. Next summer she will be out in her yard experimenting with plants to see which ones grow best in her wetland environment. And most of her guests will think she is only gardening.

Sharon Chickering likes to watch things grow at high elevations from her Leadville home.