Wetlands system recycles building's wastewater
provided by North Carolina State University
alford House believes wastewater is too precious to dump down the drain. House, a North Carolina State University water quality specialist, has underscored his point by creating North Carolina's first and only self-contained wastewater treatment system for an office building. The system which uses a constructed wetland to imitate natural processes purifies and reuses 1,200 gallons of sewer water daily from the 60 employees who work in the building, a refurbished schoolhouse on the shore of Jordan Lake in Chatham County, NC.
"We think of it as mimicking nature," said House, who works for NC State's Water Quality Group. "Nature has been cleansing water for millions of years, so we figure it's got the process figured out pretty well."
Like nature, House's system uses soil, plants and microscopic organisms to filter and treat the wastewater. The treated wastewater is used to flush toilets in the building and to irrigate the lawn and foundation plantings.
"It's clear, it sparkles, and it looks like it's right out of the tap, but it has nutrients in it, so it's liquid fertilizer," House explained. With the addition of a few minor cleansing steps, the water could be made suitable for drinking.
Without the system, the schoolhouse-turned-office building would probably still be an abandoned eyesore, because it's too remote to be hooked up to any municipal wastewater systems. The soils at the site are unsuitable for traditional wastewater treatment options.
Built in the 1940s, the Bells School building -- named for the rural community it served in eastern Chatham County -- housed first a public school and then a parochial school before closing in the 1970s. In the mid-1990s, Lyle Estill, president of software distributor EMJ America, Inc., paid to have it renovated. EMJ America and two smaller businesses are now located there.
"There's no question that it's enhanced the facility, in addition to making it possible," Estill said of the wastewater recycling system. "Giving a tour of the building is greatly enhanced by the greenhouse and the courtyard. It's a great place to bring a customer, to bring a client."
In the spring, EMJ received a Governor's Award for Excellence in Waste Reduction from the NC Department of Environment and Natural Resources, in part for its sponsorship of the water recycling project.
The wastewater treatment system has three major components: A "hill/marsh" wetland that mimics a set of sand dunes around a marsh; a wetland designed to flood and drain like a tidal marsh; and a set of greenhouse planters filled with tropical plants. Together, those components create a web of life in which tiny microbes transform waste nutrients into liquid fertilizer taken up by the plants, or into harmless and odorless gas.
Each day, 1,200 gallons of wastewater from the building flow into a 2,000-gallon septic tank near the building's courtyard. Every six to eight hours, the wastewater is released automatically into the "hill/marsh" wetland. As the water flows through three sand filters (the so-called "hills"), sand, microbes and plant roots transform and store potential pollutants. The water then flows into the "tidal marsh" wetland. The flooding and draining cycles of the wetland are controlled to influence the flow of nitrogen and phosphorus from the system.
The water is then disinfected by ultraviolet light and diverted to the greenhouse, where tropical plants take up or transform the small concentrations of remaining nutrients. Water leaving the greenhouse, on its way to being reused in the building, is treated with chlorine as a final disinfection. The entire process takes about 10 days.
The system also serves aesthetic and educational purposes. Benches in the courtyard and greenhouse make them inviting places for employees to take a break. And House uses the system as an outdoor classroom to teach children about how natural systems work, and about how they -- as humans are part of those systems. "This is applied ecology," he said.
Water is not the only natural resource reused in the system: crushed building brick and decking made from recycled plastic and sawdust are used in the exterior courtyard, and windows from a condemned building were utilized for the greenhouse.
House has evaluated similar designs in a wide variety of situations and believes the approach has many applications, especially where expensive conventional wastewater treatment systems are not feasible -- including small communities and buildings in rural areas such as Chatham County. With some alterations, the system could be maintained inside a building, making it useful in urban environments and colder northern climates. Scaled down to one-third its current size, he adds, the design would be a cost-effective wastewater treatment option for a home.
House is now developing water recycling projects in several areas, including Gates and Craven counties, and is developing a way to monitor the systems' functioning and nutrient content remotely, by Internet. "If I can get measurements in real time, I can make adjustments immediately, rather than having to send water samples to a lab and then making adjustments in person," he said.
|For more information about House's wastewater treatment system, look on the Web at www.waterrecycling.com.|