Is treated wastewater safe for agriculture?

IN MANY arid parts of the world, treated sewage water is used to irrigate crops. Whilst a common practice, concerns about its health and environmental effects are often raised. Just how safe is it to consume vegetables grown in fields irrigated with recycled water?

Recycled water originates from wastewater that flows into the municipal sewage treatment plants. As it undergoes processing, the resulting water known as effluent is safe to consume, although it may still contain traces of pharmaceutical and personal care products (PPCPs) such as shampoo, prescription drugs, cosmetics, and other impurities. Several studies have been made to see how much is absorbed by plants. But the first-ever research done under realistic conditions was carried out by researchers from the University of California- Riverside. Their study is also the first to focus on 20 PPCPs in different crops.

“The levels of pharmaceuticals and personal care products that we found in food crops growing under real-world conditions were quite low and most likely do not pose any health concern,” said study leader, Jay Gan, Ph.D. “I think this is good news. These substances do not tend to accumulate in vegetables, including tomatoes and lettuce that people often eat raw. We can use that information to promote the use of this treated wastewater for irrigation.”

A lab member, Xiaoqin Wu, found that crops absorbed several types of PPCPs such as triclosan (anti-bacterial ingredient), caffeine, tranquiliser, and medication (such as one for epilepsy). He said that leafy vegetables absorbed the highest amounts of PPCPs.

The study was presented at the 246th National Meeting & Exposition of the American Chemical Society (ACS) in Indianapolis, Indiana, and was funded by the U.S. Department of Agriculture’s National Institute of Food and Agriculture.