Plant May Help Wastewater Treatment
Paul Skillicorn spreads the root and tiny green leaves of one of the world's smallest flowering plants, which he thinks may be the answer to problem hog lagoons and aging wastewater treatment systems
Paul Skillicorn spreads the root and tiny green leaves of one of the world's smallest flowering plants, which he thinks may be the answer to problem hog lagoons and aging wastewater treatment systems.
"This duckweed is a living mat for organisms," Skillicorn said as an inchworm wiggled in his hand through fronds the size of a needle's eye.
Skillicorn, who spent nearly a decade teaching Third World communities how to harvest duckweed for a profit, says the plants absorb pollution-causing nutrients from waste. The plants then can be harvested, dried and made into pellets for animal feed.
The swine industry has shown lukewarm interest so far in Skillicorn's ideas, although he has a makeshift duckweed system at one hog farm in Greene County, about 60 miles east of Raleigh. But the Greene County town of Hookerton, faced with a $2 million price tag to pipe its waste 10 miles to Snow Hill, wants to test it.
While obstacles remain, a $790,000 state grant is waiting for Hookerton to become the first municipality in North Carolina -- and only a few dozen nationwide -- to become reliant on a duckweed system.
Skillicorn said the future of small towns can hinge on wastewater capacity. Without room for expansion, development won't happen.
"Everybody treats it as nothing," Skillicorn said, "but they don't think it through of just how profound wastewater capacity is."
Laurel, Del., a town of 3,800, added a duckweed finishing pond to its three-lagoon system because of a high algae concentration. Pollution levels are down, and the duckweed is harvested and made available to all residents as compost.
"It's done a pretty good job, although it's been a little more work than what we thought at times," said Al Adkins, Laurel's public works supervisor.
Hookerton's three-lagoon system, similar to Laurel's, becomes less efficient in killing algae and bacteria when lagoons grow warmer in the summer, and it has paid the price.
The town was fined $3,689 by the state for violating pollution limits at Contentnea Creek in the early 1990s and $3,000 last year, according to state regulators. Since January 1999, it has been operating under a special monitoring pact with the state.
"The system is outdated, so it's been a worry," Hookerton board member Ken Garris said.
Then Hookerton officials heard about Skillicorn, who moved here in 1998 after setting up duckweed-based wastewater treatment systems in Bangladesh and Peru for a decade through a nonprofit organization. He hopes to make a living with his firm, The Duckweed Co.
"I was looking for a place with intensive animal operations, so I thought, 'Why not come to North Carolina?'" said Skillicorn, an Australia native who is now an American citizen.
Skillicorn recommended that Hookerton install 26 greenhouses, each 100 feet by 15 feet. Untreated waste from the first lagoon would enter the greenhouses, where duckweed would feed off nutrients in the waste, growing rapidly. Nutrients dumped into rivers and streams generate algae blooms that rob waters of oxygen, hurting plant and animal life. But under Skillicorn's plan, duckweed would break down the nutrients while removing those pollutants from the water.
Workers would harvest duckweed daily and take it to a farm to dry out, in the process killing any pathogens that remain. The resulting olive-green material would be sold to feed operators for livestock.
"What we've got is the same kind of protein levels as the soybean," Skillicorn said as he handled some dried duckweed on a 2,000-head hog farm in Snow Hill, where he set up a greenhouse to treat hog waste.
He said the duckweed system would reduce nitrogen levels in the raw waste Hookerton discharges into Contentnea Creek from 3.6 pounds per day to 1 pound. The amount of fecal coliform would be cut by 75 percent.
Eventually, the town's two other lagoons would be eliminated, because expanding a duckweed system's capacity is easy: Add more greenhouses. Skillicorn said Hookerton could expand from its current discharge limit of 60,000 gallons per day to 200,000 gallons with the duckweed system.
Administrative costs would be about $30,000 a year, and the capital cost would be a third the cost of piping Hookerton's waste to Snow Hill, Skillicorn said. "We're making more promises than any other plan in the state and in the world," he said.
Skillicorn said duckweed could become an option for dozens of North Carolina towns with aging treatment systems that violate state pollution controls. Many face tough financial times should they hook up to a larger system.
Encouraged by state environmental secretary Bill Holman, the state Clean Water Management Trust Fund agreed in November to give Hookerton and its 515 residents a $790,000 grant for the duckweed system. Some red tape must be negotiated before Hookerton gets the money, but amid concern there is hope.
"There was very favorable reception to the project," said David McNaught, the outgoing executive director of the trust fund.
Some state regulators are skeptical of duckweed's effectiveness. A state Division of Water Quality official who reviewed the project for the trust fund said duckweed would "offer little, if any, improvement" over simply installing additional filters.
However, Holman said duckweed might be Hookerton's best option, given the high cost of tying into a regional system.
Water quality spokesman Ernie Seneca said the division prefers regional systems because they are easier to monitor, and with duckweed, "you're talking about an innovative technology system."
Hookerton leaders said piping waste to a regional system would limit Hookerton's wastewater capacity, stifling any growth it might realize from the Global TransPark, a projected air and industrial park in nearby Kinston. Mayor Kim Purser says if the town cannot offer new industry sewer and water, it has nothing to offer.
"If I'm a developer and I want to put in 100 homes, do I go mess around with Hookerton?" Skillicorn said. "No. Instead ... I go to Raleigh."
Some might consider Skillicorn an environmental crusader, but he said his ideas make financial sense.
"A tree-hugger is not useful unless what he's doing is making money," he said. "And what he's doing must make more money than what's being done right now."
Duckweed refers to species of free-floating, stemless aquatic plants touted for their uses in waste treatment, animal feed and pharmaceuticals.
Known by botanists under the family of Lemnaceae, duckweed is believed to be both the world's smallest-flowering and fastest-growing plant.
It grows 20 times faster than corn, doubling in size within a few days through a natural cloning method. It can tangle the lines of recreational fishermen casting near duckweed along still, freshwater areas where the plants thrive.
North Carolina is a common habitat for duckweed, whose fronds range in size from a pin head (genus Wolffia) to under a centimeter in length (Lemna and Spirodela). Wolffia species do not have roots, while Lemna and Spirodela have one or a few roots that dangle in the water.
Duckweed can be used to cleanse wastewater, reducing nitrogen and phosphorous in human waste.
Paul Skillicorn, who is attempting to set up a wastewater treatment system in the town of Hookerton, N.C., and other researchers also believe it could clean up hog waste, making lagoons unnecessary.
Duckweed produces more protein on average than soybeans. It can also be used to feed exotic fish being raised for aquaculture.
North Carolina State University researcher Anne-Marie Stomp has been working to genetically engineer duckweed to produce proteins such as insulin more cheaply and in greater quantities than through traditional methods. Stomp applied for a patent for her procedure and began Biolex Inc., a plant biotechnology company.
As patents on the oldest protein drugs expire, duckweed could become "the premier protein production system of the 21st century," Stomp said.
She said duckweed clones itself naturally, creating an identical copy of its parent, and its high protein content and rapid growth could be used in a controlled environment.
For more information on duckweed, check out http://www.mobot.org/jwcross/duckweed/