livestock

Treating manure doesn’t remove all the antibiotics

Two of the most elite waste treatment systems available today on farms do not fully remove antibiotics from manure, research finds.

“We were hoping that these advanced treatment technologies could remove antibiotics. As it turns out, they were not as effective as we thought they could be.”

Each year, farmers in the US purchase tens of millions of pounds of antibiotics for use in cows, pigs, fowl, and other livestock. But when the animals’ manure becomes fertilizer or bedding, traces of these medicines leach into the environment, raising concerns that agriculture may be contributing to the rise of antibiotic-resistant bacteria.

New research offers troublesome insights with regard to the scope of this problem.

Both technologies—advanced anaerobic digestion and reverse osmosis filtration—leave behind concerning levels of antibiotic residues, which can include both the drugs themselves and molecules that the drugs break down into.

In addition, the research uncovers new findings about solid excrement, which is often filtered out from raw, wet manure before the use of treatment technologies.

Two treatment options

To conduct the research, scientists visited two dairy farms in Upstate New York.

Both facilities extract much of the solid matter from cow manure before subjecting the remaining sludge to high-tech waste management techniques. To process the remaining goop, one farm uses advanced anaerobic digestion, which employs microorganisms and pasteurization to break down and convert organic matter into products that include biogas, while the other farm uses reverse osmosis, which passes the slurry through a series of membranes to purify water.

Researchers found that this solid matter may contain higher concentrations of antibiotics than unprocessed manure, a discovery that is particularly disturbing because this material often goes into the environment as animal bedding or fertilizer.

“We were hoping that these advanced treatment technologies could remove antibiotics. As it turns out, they were not as effective as we thought they could be,” says Diana Aga, professor of chemistry at the University at Buffalo.

She does offer some hope, however: “On the positive side, I think that a multistep process that also includes composting at the end of the system could significantly reduce the levels of antibiotics. Our earlier studies on poultry litter demonstrated that up to 70 percent reduction in antibiotics called ionophores can be achieved after 150 days of composting. Testing this hypothesis on dairy farm manure is the next phase of our project, and we are seeing some positive results.”

The research on reverse osmosis filtration appears in the journal Chemosphere. The study on advanced anaerobic digestion—a collaboration between the University at Buffalo and Virginia Tech—appears in the journal Environmental Pollution.

It’s not just farms

Though the new research focuses on dairy farms, the findings point to a larger problem.

“Neither of the treatment systems we studied was designed to remove antibiotics from waste as the primary goal,” Aga says. “Advanced anaerobic digestion is used to reduce odors and produce biogas, and reverse osmosis is used to recycle water. They were not meant to address removal of antibiotic compounds.

Tons of gull poop mess up nearby water

“This problem is not limited to agriculture: Waste treatment systems today, including those designed to handle municipal wastewater, hospital wastes, and even waste from antibiotic manufacturing industries, do not have treatment of antibiotics in mind. This is an extremely important global issue because the rise of antibiotic resistance in the environment is unprecedented. We need to start thinking about this if we want to prevent the continued spread of resistance in the environment.”

Aga is a proponent of the “One Health” approach to fighting antimicrobial resistance, which encourages experts working in hospitals, agriculture, and other sectors related to both human and animal health to work together, as humans and animals often take the same or similar antibiotics.

Source: University at Buffalo

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