Research Raises Questions About Recycled Wastewater For Produce

Eating produce grown with recycled wastewater may have drawbacks, new research indicates.

“A new study shows that eating vegetables grown using reclaimed water boosts urine levels of carbamazepine, an anti-epileptic drug commonly detected in wastewater,” Chemical & Engineering News reported.

The study, recently published in Environmental Science & Technology, noted that concerns have been raised about reclaimed water contaminated by pharmaceuticals.

“This study focuses on carbamazepine, an anticonvulsant drug which is ubiquitously detected in reclaimed wastewater, highly persistent in soil, and taken up by crops,” the study said.

The findings, per the study:

In a randomized controlled trial we demonstrate that healthy individuals consuming reclaimed wastewater-irrigated produce excreted carbamazepine and its metabolites in their urine, while subjects consuming fresh water-irrigated produce excreted undetectable or significantly lower levels of carbamazepine.

The researchers did not expect such pronounced results. Ora Paltiel, study coauthor, told Chemical & Engineering News: “We were very surprised that the effect was so clear.”

“Empirically, it’s obvious that everyone who is exposed to a seven-day diet of reclaimed water is going to have a quantifiable level of this drug in their urine. These are nanogram per liter levels — they are four orders of magnitude away from levels of if you were taking the drug,” Paltiel said, per the report.

“Reclaimed wastewater can be a partial solution to agricultural problems in semi-arid regions, but we have to be cognizant that there are potential exposures from this” Paltiel said.

The researchers tested for the drugs using a method they developed in a previous study, recently published by Environmental Pollution. “A novel trace determination of carbamazepine and metabolites in urine is presented. A sample preparation optimization for all the compounds was performed,” the study said.

In the latest study, the researchers provided volunteers with produce, including lettuce, tomatoes, cucumbers, peppers, and other vegetables, according to Chemical & Engineering News.

“For the first week of the study, participants received either vegetables grown on a farm irrigated with reclaimed wastewater or vegetables grown on an organic farm that only used freshwater. For the second week, the reclaimed-water group received freshwater-grown produce, and the freshwater group — because of a produce supply issue — received produce from a supermarket, which likely included a mix of produce grown with freshwater and reclaimed water. Everyone received bottled water from the researchers to drink to control for other sources of water contamination,” Chemical & Engineering News reported.

The safety implications of the findings remain unclear. Alistair Boxall, a professor of environmental science at the University of York, told Chemical & Engineering News: “We don’t really know much yet about the effects of low-level but very long-term exposure.”

Benny Chefetz, a study coauthor, explained that treating wastewater does not necessarily remove all contaminants.

“Treatment for wastewater used in agriculture generally does not remove these trace chemicals because purifying such a large quantity of water to drinking water standards would be prohibitively expensive,” Chemical & Engineering News reported, citing Chefetz.

Environmentalists and water experts have also raised concerns about the use of recycled water to irrigate parks.

Research undertaken at Denver Water’s request makes “a persuasive case that foliage and soils in city parks treated with Denver Water’s recycled product contain high amounts of sodium — which, over time, can be particularly lethal to conifers, since they draw water from their roots most of the year,” according to a Westword report.

To read more about recycled water visit Water Online’s Water Reuse Solutions Center