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Engineered wetlands for wastewater treatment can overcome a myriad of location challenges ranging from aesthetic demands to varied topography to complex soil configurations.
By Carol Brzozowski
From campgrounds to resorts, from residential homes on golf courses to farms dotted along rural byways, wetlands are being engineered as a solution to wastewater treatment challenges. Engineered wetlands are often the best option in an environment or location with restricted space or complicated configurations. The use of wetlands for onsite water treatment also allows for aesthetic control by facilitating the creation of a system that fits into the surrounding environment. One final and increasingly popular asset to engineered wetlands involves the ability to easily add a water reuse component to the system.
Innovation and Education
Some of the most challenging wetlands jobs have occurred on behalf of the Boy Scouts of America (BSA). Being good stewards of the environment is woven through the BSA programs. Part of that stewardship is called “Leave No Trace,” in which the boys learn such principles as properly disposing of any waste—including wastewater.
The standard practice for Boy Scout camps developed before the 1950s was to construct a pit latrine on a cleared campsite. But these days, that’s simply not enough. Camps are becoming a more popular destination for Boy Scouts.
“Many of these facilities were built in the 1950s before interstate travel was common,” points out John Stewart, consulting engineer for the BSA. “As a consequence of changing times, shifts in population, and consolidation of property, more and more kids are attending camps that were designed for 250 to 300 youth, staff, and leaders.
“When we exceed these design parameters, we have to keep a watchful eye on the water and wastewater systems given their age, capacity, and technology.”
Additionally, new camps are being built around the country in rough and remote terrain that require a high level of environmental stewardship that ties into the corporate values of the BSA and the Outdoor Code taught to all boys.
In 2000, the National Scout Council launched an educational program for its individual Boy Scout Councils that own and operate each camp in response to the need to address water and wastewater infrastructure needs in the BSA’s aging and developing camps nationwide. The effort provides expertise, guidance, and sometimes funding.
North American Wetland Engineering (NAWE) in White Bear Lake, MN, is an ecological engineering company co-founded by Curt Sparks, a former regulator, and Scott Wallace, a wastewater operator and design engineer. The company has engineered more than 200 water and wastewater projects throughout the United States. NAWE has helped provide the BSA with onsite wastewater treatment solutions on two of its three United States–based high-adventure camping properties.
One such camp is the Charles L. Sommers Wilderness Canoe Base. The high-adventure camp is located in Lake County, MN. NAWE was called to the camp in March 2000 after the site’s wastewater system had been cited for unauthorized discharge to Moose Lake in the Boundary Waters Canoe Area (BWCA). Minnesota Pollution Control Agency (MPCA) rules prohibit discharges from a wastewater system to the BWCA.
The aerated activated-sludge package treatment plant that had been in service for decades at the Canoe Base was in need of major repairs. Its discharge went to a beaver pond that would overflow to Moose Lake during heavy-rain events. The package plant was rated at a capacity of 15,000 gallons per day. Following treatment, the water discharged into a 1.2-acre lagoon. Flow variations at the Canoe Base caused the package unit to be prone to upset conditions.
A major windstorm hit the BWCA in July 1999, blowing down many trees. While areas with massive destruction were logged and cleared, uprooted trees caused damage to the wastewater system. The storm, combined with beaver activity and years of accumulated sludge and debris in the lagoon, caused the lagoon dikes to leak, with treated wastewater seeping out to Moose Lake.
The Boy Scout base, nestled among rock outcrops, clear glacial lakes, and rugged terrain, is a picturesque and desirable recreational destination. But it also presented a challenge for proper wastewater management. The Boy Scout property is bordered on the north and west by the BWCA, and thick forest and wetland areas border it on the south and east. Only one road leading to the south side of the Canoe Base provides access to motorized vehicles.
Soil conditions vary, with much of the site cleared of soil after tens of thousands of years of influence of successive glacial periods. A range of soil conditions starts with no soil and to 20 to 30 inches of soil in some of the hillside areas. The soil is mainly sandy loam to silt loam. Fractured bedrock lies below layers of the silt loam.
For wastewater treatment of the highest effectiveness, NAWE replaced the package plant with an insulated subsurface-flow wetland with forced bed aeration. Two shallow disposal drainfields were constructed—1,500 gallons per day for winter use and 9,000 gallons per day for summer use. Surface-water discharge was eliminated and biosolids in the old beaver pond were stabilized in situ.
At another BSA high adventure camp in Islamorada, FL, Scouts are taught about survival and the natural world in a setting that is accessible only by boat and wading onto shore. The camp has no running water, electricity, or permanent structures. From May to September, all of the campsites at the Florida Sea Base are filled. Most food comes to the camp prepared and packaged [as in MREs (Meals Ready to Eat)] and everything entering the natural eco-adventure camp leaves with the campers.
Although there is hardly any food preparation, 4 gallons of wastewater per day are generated through the washing of pots and eating utensils. The BSA sought a wastewater treatment system to treat that small amount and meet strict nutrient reduction standards for the Florida Keys.
NAWE recently designed and installed a constructed wetland with botanist-selected native plants to treat the dishwater generated by meal consumption. The constructed wetland system removes the phosphorus, biological oxygen demand, suspended solids, and nitrogen from the graywater left after dishwashing. Phosphorus is of particular concern because of its harmful effects on plant and algal growth.
The system NAWE designed includes a small sand filter in a polyethylene drum at each campsite, with 15 graywater receiving units servicing the 17 campsites. Two campsites are close enough to other sites so that a double system was utilized. A 55-gallon barrel was used to house the sand filter, which is situated in a constructed lined wetland bed measuring 8 feet by 10 feet. The scouts pour the graywater into the top of the barrel, modified to include a disposable coffee filter supported by a plastic screen. Food particles are caught and disposed with other solid waste. After graywater enters the wetland bed—filled with phosphorus-absorbing material—most of it evaporates and is taken up by the native plants that disguise the wastewater treatment system as part of the surrounding environment. In the case of heavy rainfall or otherwise high use, treated effluent flows through the bed into a subsurface discharge system. The NAWE wetland system was selected because the material could be delivered by boat and waded into shore.
In addition to the graywater wetland treatment system, the campers also use composting toilets for their other sanitary needs. The system provides an added benefit: an educational opportunity for scout leaders to discuss water treatment, recycling, and environmental protection.
To date, NAWE has worked on about 30 projects in 10 states for the BSA. It’s an effort that’s close to Wallace’s heart, as he is a former scout and now a leader in his son’s scout troop. Additionally, “It’s very rewarding for our staff to solve the real needs in often pristine environmental settings,” Wallace notes.
Scouting officials praise NAWE for its quick assessment process and innovative ecological solutions, pointing out that the company is onsite in a timely fashion and its employees are adept at working with local regulators in working out solutions. They say it’s in keeping with the scouts’ mission of respect for the environment and a willingness to do what’s needed to improve water and wastewater systems.
Aesthetic Needs, Challenging Topography
Lutsen Resorts was established in 1885 as the oldest resort in Minnesota. Lutsen Sea Villas Resort was built in 1968 on the North Shore of Lake Superior in Lutsen, MN. Some 31, two-bedroom suites fed into the onsite septic system, which had reached its lifespan and did not meet current codes. Replacing the conventional onsite septic system—which would occupy more land—was not a realistic option for the management company.
Some of the challenges in addressing the site-planning situation included shallow bedrock, high water tables, and setback requirements from Lake Superior. Aesthetics was a significant concern as well, says Scott Harrison, president of Lutsen Resorts Co.
“For me, the challenge was to understand what alternatives there were to conventional systems,” he says.
Resort owners realized the need for a wastewater treatment system that would have a lifespan to match the needs of resorts and developments along the North Shore. Limited land area called for innovation in design approach with a system that is aesthetically pleasing when integrated into the resort environment.
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Photo: North American Wetland Engineering |
| More interstate travel means campsites are seeing more traffic than ever before. |
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Photo: North American Wetland Engineering |
| Shallow bedrock, high water tables, and setback requirements from Lake Superior
were just some of the obstacles faced by NAWE. |
Harrison met with the NAWE executives to discuss the science of wetlands engineering.
“I was intrigued by the alternative way of dealing with waste horizontally to a subsurface-flow treatment system instead of vertically,” he says. “I had enormous respect for how they approached the problem and how they dealt with their client. They educated me and then allowed me to educate the owners whose property we represent.
“They designed the subsurface-flow wetland with a forced bed aeration system with 6,000 gallons per day, monitored the installation of the system through the contractor I hired, and then continued to monitor that as they have since the installation primarily to help us understand what was happening long-term.”
The design incorporated the extensive use of existing water-use records, resulting in a time-based flow equalization system to accommodate peak flows. After wastewater goes through wetland treatment, the effluent is disposed of in two pressure-dosed mounds. Lowboy septic tanks were utilized to avoid groundwater and minimize blasting. The area’s clay soils were not suited to conventional septic tank use, so a wetland-treatment cell was constructed. And when motor vehicles traverse US Highway 61, drivers see nothing but a variety of ornamental wetland plants as part of the vegetation.
Lutsen Resorts would go on to use NAWE on two other sites, even though there were not equivalent soil challenges. The second installation was done at a 24-unit, 12-building condominium, constructed in 1998.
“We went to North American Wetland Engineering in 1997 with the plan and they designed it. Despite the fact we had dramatically better soil and didn’t have bedrock problems, I wanted the same technology,” Harrison says.
“I wanted the subsurface treatment system. I wanted a lot of plant life that drove off a lot of water in the summer through transpiration,” he says. The system was designed for 4,000 gallons per day.
In the third installation, designed for 22,000 gallons per day, the system was designed to take all of the load from the main lodge for the food and beverage operations, laundry, and rental rooms. It also was designed to include all of the long-term development plans for which Lutsen has a county permit that will include 17 more three-bedroom town homes, employee housing with 22 efficiency apartments, and a potential 24-unit motel.
“We scaled everything for where we thought we could be and sized it for that,” says Harrison. “In this particular case, because it was more than 10,000 gallons per day, we had to go through the permitting process with the State of Minnesota.”
Sparks’s experience as a former regulator helped in navigating the permitting process, Harrison points out.
“So we permitted the 22,000 gallons here and are using 50% of it right now,” says Harrison.
The system is more conventional, he adds. “All of the effluent goes to a pre-treatment filter bed and is recycled several times through the aerating gravel filter bed. Subsequent to that treatment, it’s sent out to a conventional treatment field and it’s 99% treated.”
NAWE is onsite each month to monitor the systems as a condition of getting the permits from the Minnesota Pollution Control Agency for the latest installation. The other two systems are monitored every three months.
Incorporating Water Reuse
In another residential application, NAWE was instrumental in setting up the wastewater treatment needs for the Ponds, a 223-unit residential development on 410 acres in Oak Grove, MN. The residential units adjoin an 18-hole golf course.
Several wetlands made the layout of a wastewater treatment system a challenge, so developers sought a solution that would be compact and efficient to meet the minimal space that could be set aside.
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Photo: North American Wetland Engineering |
In 2002, NAWE created a vertical-flow treatment wetland with a design flow of
86,300 gallons per day using recirculating gravel filter technology. |
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Photo: North American Wetland Engineering |
| Engineered wetlands have practical applications for agricultural wastewater. |
In 2002 NAWE created a vertical-flow treatment wetland with a design flow of 86,300 gallons per day. The approach utilizes recirculating gravel filter technology. The design also included a gravity flow sand filter and sodium hypochlorite disinfection track. The entire footprint is on less than 1.5 acres.
A reclaimed water pond provides storage for treated water to irrigate the golf course. The golf course’s water appropriation by the state’s Department of Natural Resources had been limited and the reclaimed water meets the deficit in what was needed for favorable turf grass growing conditions.
Connexus WaterWays, which is affiliated with Connexus Energy in Ramsey, MN, owns and operates decentralized wastewater systems throughout Minnesota on behalf of homeowners’ associations. Connexus took over operation of the system after it was installed. Rod Morton, a manager of corporate development with Connexus WaterWays, says in the case of the Ponds, soil conditions and the water table played into the challenges in designing the system.
“The soil conditions there would have taken up so much more land to incorporate the disposal of the wastewater,” he says. “That’s why they went to the pond-type technology and used it to irrigate the golf course.
“Having the golf course there probably helped drive up some of the land prices for the lot and drove the demand of people purchasing those lots, and at the same time, the golf course was able to receive a benefit from using the reclaimed water.”
Minnesota hasn’t focused on water conservation to the extent of other states “because we do have the abundance of water through the lakes, rivers, and streams,” says Morton.
“It doesn’t mean that it isn’t important, that we should not conserve it when appropriate,” he says. “In the bigger picture, I do think it does help our aquifers to reuse the water as much as we can. And it is regenerating in the same area where the water was taken from.
“The biggest part of the whole collection or treatment system was the disposal. This made a very efficient use of land to be able to dispose the water on an area that’s being utilized for something that has value, versus just a drainfield.”
The important part from the view of Connexus WaterWays as the wastewater system’s owner and operator was being able to get legal agreements with the golf course to be able to dispose the water on the golf course.
“One of the concerns was if there wasn’t that agreement for somebody to take the water, how do we get the water out of the retention pond? That is a very key factor that was a real learning experience,” says Morton.
“It’s almost best to work from the back end forward and ask, ‘How am I going to get rid of the wastewater after it’s treated?’ I need to really firm up that language to make sure I have a secure place for using that reclaimed water. Without that disposal mechanism for the wastewater, the system basically doesn’t function. That was real learning experience on our side, and in the future we’ll put more emphasis on that in the beginning of the process.”
NAWE also has been instrumental in engineering wetlands for agricultural wastewater. The company did such a project in Sleepy Eye, MN, where tertiary treatment wetlands have been installed at four facilities of Christensen Farms, an agricultural firm that operates farms throughout the Midwest.
Earthen storage basins were installed at the sites with tertiary treatment designed to reduce nitrogen levels in the reuse stream. Supernatant is discharged from the anaerobic lagoons to a pre-aeration cell for pretreatment before the flow is introduced into a free-water surface wetland designed to polish the water and provide a natural habitat for water fowl. The treated water, pumped from the wetlands, is reused for barn washwater.
Carol Brzozowski is a journalist in Coral Springs, FL.
OW - September/October 2007
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