Conscious Choice: Treating Wastewater the Natural Way

June 2002

Treating Wastewater the Natural Way

by Mary Boldan

For centuries, sewage and wastewater have been looked upon as nasty and embarrassing problems to get rid of. For many of us, waste is whisked away to complex mechanical or chemical treatment systems that, many times, lead to more environmental problems as well as ongoing costs. The federal government spent billions of dollars on centralized sewage treatment plants; however, the Congressional Research Service admitted in 1999, "Much of the surface water of the planet is in a state of ill health because of misplaced nutrients, and a main contributing culprit is misplaced human excreta."

Within the last few decades, interest has steadily increased in using natural physical, biological, and chemical aquatic processes for the treatment of household wastewater, especially the effluent from septic tanks. This interest has been driven by growing recognition of the natural treatment functions performed by wetlands and aquatic plants.

Wetlands have evolved to be one of the most productive and species-rich ecosystems on the planet, and have a natural, innate ability to treat wastewater. Wetlands are not necessarily all the same. In fact, the different names we have for wetlands represent some of the different categories of wetland: swamp, marsh, bog, fen, wet meadow, and slough are some of the most common. In all, over 2,000 types of soils can occur in wetlands. Plant types, water, and geological conditions vary, as well.

Many plant species have evolved symbiotic relationships with micro-organisms and can both oxygenate and purify waters with high levels of organic waste. The establishment of wetland vegetation improves water quality by recreating the natural wetland filtering mechanisms; the most important of these mechanisms is the ability to "uptake," or absorb nitrogen.

When wetland plants uptake nutrients, they filter the water. The nutrients are then absorbed by the plants. The plants use some of them and pass off some into the air through the process called trans-evaporation; thus they filter off the nutrients that would otherwise support excessive algae.

"Sewage is a wonderful, untapped resource. It’s been treated like this toxic substance
that we have to get rid of, but really it’s a valuable commodity."
— Mark Nelson, vice president, Wastewater Recycling Systems,
The Planetary Coral Reef Foundation

Constructed Wetlands

In response to growing interest in wetlands, ecological engineers have begun designing systems that consider waste an unused resource and filter it using the purification process found in the wetlands. These systems recycle water and nutrients back into nature in a way that does not upset the local ecology.

Sustainable Strategies, of Concord, Massachusetts, has designed an ecological engineered wastewater system called the Wastewater Garden. The process is simple. Toilets drain into scientifically engineered gardens, an impervious garden trench growing a variety of plants that essentially eat, drink, and breathe away the contaminants found in the wastewater. Diverted from high-cost treatment service plants, the wastewater essentially nourishes plants. The wastewater garden can do what a septic system does, but beyond this function, it is not like a septic system at all. It is a zero discharge system for the complete utilization of wastewater, resulting in the end products of plant biomass, evaporated water, carbon dioxide, and heat.

Closer to home, Prairie Crossing in Grayslake, Illinois, contains clustered housing surrounded by a prairie swale system that passively filters water as it flows through 175 acres of prairie, and finally into 18 acres of wetlands and 27 acres of lake. The system was designed by Applied Ecological Services, Inc. (AES) of Brodhead, Wisconsin. Steve Apfelbaum and Jack Broughton of AES "believed that by replicating the historic prairie-to-wetland ecosystem gradient, the majority of contaminants associated with urban land use could be bio-filtered and assimilated within the prairie swales before it reached the wetlands and lake."

However, such ecological wastewater treatments are not limited to large-scale projects. Homeowners, especially those with septic systems, are slowly adopting these systems, too. Most septic tanks are inadequate and are overflowing or backing up, spreading bacteria into lawns and homes, polluting the groundwater, and breeding insects. In addition, the standard septic tank only removes 60 to 70 percent of the organic waste in domestic wastewater, while newer alternatives can efficiently and rapidly remove 95 percent of the organic waste. While conventional septic systems usually are very effective at removing phosphorus, they do not effectively remove nitrogen, found abundantly in urine. According to Don Jones, a Purdue Cooperative Extension Service Agricultural engineer, "A conventional septic system gets rid of only 10 percent to 20 percent of the nitrogen. Alternative systems, such as constructed wetlands, remove 80 to 85 percent."

Constructed wetlands are created specifically for the treatment of wastewater, stormwater, or agricultural runoff. Duplicating the process that occurs in natural wetlands, constructed wetlands are complex, integrated systems where water, plants, animals, microorganisms, and the environment interact to remove contaminants and improve the water quality.

Wetland systems work on the principal that aquatic plants transfer oxygen from above-surface leaves to sub-surface roots. Aerobic bacteria attach to the roots, while anaerobic bacteria attach to the rocks. The effluent that flows through the wetland is treated by the action of the bacteria attached to the plant roots and rocks. After treatment, the water is released, usually through a drip system that irrigates the landscape.

Most constructed wetlands that treat domestic wastewater are subsurface systems. The wastewater is not exposed on the surface of the yard, which eliminates foul odor, insects, or safety concerns. Wastewater first flows to a septic tank that acts as a primary treatment system. Here solids are settled. From the septic tank, the effluent flows through a distribution pipe buried in rock or gravel into vegetated submerged beds. According to Kevin Tungesvick, nursery manager of Spence Restoration Nursery, a wholesale nursery in Muncie, Indiana that specializes in native plants and seeds for wetlands, constructed wetlands typically include Sweet flag (Acorus calamus), Burreed (Sparganum spp.), Bulrushes (Scirpus spp.), Arrowhead (Sagittaria spp.), Arrow arum (Peltandraw virginica) and Lake sedge (Carex lacustris). He warns that cattails and common reed should be avoided due to their invasive nature.

Other Alternatives

An alternative to constructed wetlands is drip irrigation. Drip irrigation is one of the best options for homeowners like Bret and Gina Rappaport of Deerfield, Illinois, who are releasing the water to an environmentally-sensitive area. A few years back, when the Rappaports replaced their existing septic system, which was a standard underground gravel field, they decided they wanted the discharge to flow into a manmade fen. Of course, living adjacent to the Chicago River helped.

"We consider it our obligation as stewards of the land to use our property in an ecologically friendly way," said Bret Rappaport, a Chicago attorney, who has also served as president of the Wild Ones; an organization dedicated to promoting natural landscaping. He is also a champion for homeowners who must combat unfair weed ordinances when planting natural landscapes.

At first, the Environmental Health Services of Lake County had indicated that the Rappaport’s soil was conducive to a Wisconsin Mound system. No other alternative could be built under the existing ordinance without the granting of a variance from the Department of Public Health. The Wisconsin Mound system is a soil absorption system constructed above ground that uses sand fill to enhance treatment before wastewater enters the natural soil at the site. However, in order to meet the code requirements, this system would consume the entire backyard

"A Wisconsin Mound system is like a big plateau in your backyard," commented Rappaport. "In our case the mound would have had to be 100 feet long by 40 feet wide, and 4 feet high. Constructing a mound system would render my entire yard unusable, cause environmental problems, and be detrimental to the quality of life for my family and neighbors. In addition, the mound would cause significant erosion and flooding problems." In response to the Rappaport’s concern, the Environmental Health Services of Lake County suggested that the Rappaports install a drip irrigation aerobic system. The system would remove nitrogen and harmful organic matter as the wastewater traveled through a special filtering system, and discharge would flow into a manmade fen.

Aerobic systems are similar to septic systems in that they both use natural processes to treat wastewater, which includes water from toilets, bathtubs, showers, sinks, and laundry. But unlike septic (anaerobic) treatment, the aerobic process requires oxygen. Bacteria that thrive in oxygen-rich environments work to break down and digest the wastewater inside the aerobic treatment unit. The aerobic wastewater treatment is designed to treat septic tank effluent to a level suitable for surface irrigation (in the Rappaport’s case, drip irrigation) within the site. The process most aerobic units use to treat wastewater is referred to as suspended growth. These units include a main compartment called an aeration chamber in which air is mixed with the wastewater. Since most home aerobic units are buried underground like septic tanks, the air must be forced into the aeration chamber by an air blower or a compressor.

Although aerobic units are very effective, the wastewater leaving the unit cannot return to the environment until it receives a final treatment. The wastewater is pumped evenly over several layers of sand and gravel, which is located below the ground. As with any soil treatment system, the purification process is aided by bacteria that occur naturally in the sand. The sand/gravel filter removes any solids that might plug the drip irrigation system.

"The benefit of using drip irrigation is that the effluent is injected into the soil ten to twelve inches below the surface, rather than twenty-four to thirty inches as with the conventional absorption trenches," adds Don Jones. "Nearly all the biological activity takes place in the top sixteen inches of soil so there is much better opportunity for treatment of effluent."

Jones adds that drip irrigation systems have been used in the southeast United States for about fifteen years for septic system, and in the Midwest for only the last five to six years. One of the concerns is freezing during the northern winters. However, he states that if the valves work correctly, the water drains after the drip line is loaded. Natalie Kearney, Health Officer at Land Technologies in McHenry, Illinois adds that the constant use of power underground produces continuous heat and prevents freezing.

The drip irrigation system applies treated wastewater to soil slowly and uniformly from a network of narrow plastic, polyethylene, polyvinylchloride (PVC) tubing placed at shallow depths of usually six to twelve inches in the plant root zone. The wastewater is pumped through the drip lines under pressure, but drips slowly from a series of evenly spaced openings called emitters. One advantage to this system is that water is applied at a controlled rate in the plant root zone. Shallow placement of the drip emitter lines is intended to allow for enhanced evapotranspiration of effluent, as compared with the conventional subsurface disposal system.

A Home Ecosystem

Today, Rappaport’s fen is teaming with special relationships that exist between plants, insects, and animals. It is a beautiful focal point, a place for children to look under rocks and search for insects, as well as a peaceful place for people to sit. With the help of Anne Meyers of Enders Greenhouse and Pat Armstrong, owner of Prairie Sun Consultants and a frequent lecturer on wildlife landscaping, Rappaport has created a self-regulating system of native plants and other organisms to approximate as closely as possible a natural wetland ecosystem.

Fens are the rarest wetland community of great scientific interest. While their geology varies, they are all products of the seepage of groundwater to the surface. Because the drip irrigation system slowly, but constantly, releases the treated wastewater to soil, Rappaport calls his natural wetland a septic field fen. Pat Armstrong adds, "Because he is using water from the septic system, it is not very limey, but higher in nutrients. I suspect that some of his plants will grow much bigger and taller due to the increased nutrients."

The vegetation growing in the Rappaport’s fen is very similar to that of sedge meadows and wet prairies. A sedge meadow is an open wetland community occurring on saturated locations. It is dominated by sedges and forbs such as the Sensitive fern (Onoclea sensibilis), Marsh fern (Thelypteris palustris), Bottle gentain (Gentiana andrewsii), Blazing star (Liatris spicata), Swamp goldenrod (Solidago patula), Blue flag iris (Iris versicolor), Bottlebrush sedge (Carex lurida), and Monkeyflower (Mimulus ringens). The wet prairie is seasonally inundated in low spots, and includes Switchgrass, Big bluestem, and forbs such as Flat top aster (Aster umbellatus) and Ironweed (Vernonia).

Deep water is of relatively little value for much of wildlife, but the damp sedge meadow provides food for the Delaware skipper butterfly, and a hunting ground for the tiny bluebell dragonfly. Rare butterflies like the Baltimore Checkerspot depend on the white flowers of the turtlehead (Chelone glabra) and valerian for laying their eggs, and later for food for young caterpillars. The yellow-headed blackbird, marsh wren, and common snipe all depend on this ecosystem for survival.

Since using wastewater to create wetlands helps redeem wastewater from its status as befouled residue of civilized life, one may ask why such systems are not more popular. Mark Nelson, vice-president of Wastewater Recycling Systems for the Planetary Coral Reef Foundation, thinks the concept is just too simple. He believes people tend to underestimate ecology, while overrating technology. However, he strongly believes that ecological engineering, such as constructed wetlands, will find its place in the twenty-first century.

Get More Info

Illinois Department of Natural Resources

U.S. Environmental Protection Agency Wetlands page

The National Onsite Wastewater Recycling Association, Inc. (NOWRA)

National Environmental Services Center (National Small Flows Clearinghouse). The NSFC helps America’s small communities and homeowners solve their wastewater problems to protect public health and the environment.

Environmental Concern, Inc. This non-profit organization has been dedicated to wetland restoration, research, and education since 1972.

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