Engineering nature-based solutions to improve water quality on the farm

Consider the humble farm pond. It’s used to water crops and livestock. It attracts birds and other wildlife and can be stocked with fish. In a pinch, farm pond water can be used to put out fires.

But farm ponds, filled by rainfall and runoff from nearby fields, can collect numerous harmful substances, from pesticides and herbicides to traces of veterinary medicine, hormones and antibiotics found in animal manure. When water from farm ponds is used to irrigate fields, it can post a risk to food safety and ultimately human health.

Consider the humble farm pond. It’s used to water crops and livestock. It attracts birds and other wildlife and can be stocked with fish. In a pinch, farm pond water can be used to put out fires.

But farm ponds, filled by rainfall and runoff from nearby fields, can collect numerous harmful substances, from pesticides and herbicides to traces of veterinary medicine, hormones and antibiotics found in animal manure. When water from farm ponds is used to irrigate fields, it can post a risk to food safety and ultimately human health.

CAES professor Niroj Aryal, Ph.D., is seeking ecologically engineered solutions to nonpoint source pollution, His ongoing research points to several low-cost and sustainable approaches that could improve water quality in agricultural settings.

On the glove of Niroj Aryal, Ph.D., is what he calls “the worker in the wetlands,” duckweed.

“Farm pond water quality can be impacted by so many different kinds of pollutants.

My goal is to evaluate ecological engineering techniques to see how effective they are at removing these pollutants and finding innovative ways to improve these techniques,” said Aryal, an associate professor of biological engineering in the Department of Natural Resources and Environmental Design.

“We want to improve the quality of water in those farm ponds so when we use it for irrigation we can lessen the impacts on us,” he added. “Water quality and food safety — they’re connected.”

Aryal joined the CAES faculty in 2017 after earning his doctorate in biosystems engineering and environmental engineering from Michigan State University and working for two and a half years as a postdoctoral researcher with the U.S. Department of Agriculture’s Agricultural Research Service in Arkansas. In 2023, North Carolina A&T State University promoted him to associate professor and granted him tenure. He is currently serving as interim chairman of the Department of Natural Resources and Environmental Design.

Aryal is aligned with an emerging scientific discipline known as ecological engineering, which seeks to design natural and sustainable solutions to restore ecosystems and address environmental challenges. Nature has the capacity to solve many of its own problems, he said, but sometimes it needs some human assistance.

To design ecological engineering solutions to agricultural problems, “we try to use as many natural materials as possible — no chemicals, no fertilizers, no pumps,” Aryal said. “We’re looking for low-cost, natural and passive techniques that can work in the fields and be deployed by farmers. If it’s expensive, it’s not going to be adopted.”

In his latest research endeavor, Aryal is seeking ways to improve the water quality in farm ponds by removing pollutants from water runoff. His project is funded by a USDA Evans-Allen capacity grant, which supports agricultural research at 1890 land-grant universities, of approximately $600,000 over four years.

Aryal is experimenting with two methods: woodchip bioreactors and constructed wetlands. Woodchip bioreactors — simple trenches dug out and filled with cheap and available wood chips — have been proven to be extremely effective at converting nitrates found in water flowing through agricultural tile drainage networks into harmless nitrogen gas. Wetlands also are highly efficient at improving water quality.

Aryal noted that much research on biofilters has focused on their ability to remove nutrients such as nitrogen and phosphorus from groundwater. But scientists have paid relatively little attention to their effectiveness at eliminating common farm pollutants such as agrochemicals, pathogens and even antibiotic resistant bacteria.

In a greenhouse laboratory at the N.C. A&T University Farm, Aryal and his research team designed and built multiple versions of these bioreactors — solely with wood chips, with wood chips and various metals, and wetlands that incorporated peat moss and biochar, a charcoal-like substance that remains after organic materials are burned.

Aryal said he has found designs that removed significant amounts of lambda cyhalothrin and cypermethrin, two pyrethroids widely used in commercial insecticides. Other designs have been effective at lowering levels of glyphosate, a widely used herbicide, and E. coli bacteria.

Aryal already has published one paper on his current work in the journal Sustainability. A second paper has been accepted for publication, and a third is being written. He hopes his findings will spur other researchers to investigate what other pollutants and pathogens might be removed by biofilters so they can engineer more effective methods of improving water quality on farms and even urban environments.

Better water quality, he said, holds promise for solving water shortages that threaten so much of the planet.

“A good solution for our water quantity problem is to collect more runoff, but at the same time we need to improve our water quality,” Aryal said. “Ultimately, the goal is to have access to safe and abundant water for diverse uses by improving methods of conservation, protection and treatment.”