Duckweed might hold the key to removing contaminants from ponds and other bodies of water that could be harvested into animal feed.
Researchers from South Dakota State University believe the small aquatic plant could be a viable option to help remove several contaminants from lakes, ponds and streams including phosphorus, nitrates, nitrites and heavy metals that eventually could be incorporated into animal feed.
Roger Foote, coordinator for the Upper Big Sioux River Watershed Project, first encountered duckweed when he was operating a water treatment plant as a phosphorus removal facility.
“My intent was to use algae to remove phosphorus, but the processing plant became contaminated with duckweed,” Foote said in a statement. “I was removing hundreds of pounds of duckweed every week.
“It’s very prolific and can compete with algae,” he added. “It will grow until it runs out of space and prefers warm, slow-moving water.”
The researchers collected samples of duckweed at Foote’s indoor phosphorous removal facility in Watertown, South Dakota and from the Big Sioux River.
“Duckweed can grow in South Dakota and even in the North Central region, but there are limits based on the season,” Lin Wei, an assistant professor in the Department of Agricultural and Biosystems Engineering, said in a statement. “Duckweed is also easy to harvest and process.”
Wei added that the best growth occurs in the summer and the primary challenge is to control the water content—which is 80 to 90 percent in fresh duckweed.
The researchers dried the duckweed and made silage in small amounts—about seven ounces each. They then incubated the samples for 60 and 90 days.
“We saw a slight decrease in crude protein and an increase in ammonia as a protein source when we went to 90 days,” Julie Walker, an animal science professor at South Dakota State, said in a statement.
The researchers will now test how contaminant uptake, including heavy metals, will affect the feed quality, as well as figuring out cost-effective ways to reduce water content.
