Drugs, Chemicals Seep Deep into Soil from Sewage Sludge
Sewage sludge used as fertilizer on farms can leave traces of prescription drugs and household chemicals deep in the soil, according to a new study by federal scientists.
The findings suggest that the widespread use of biosolids could contaminate groundwater near farms with a variety of chemicals, including anti-depressants such as Prozac and hormone-disrupting compounds in antibacterial soaps.
“These compounds are not sitting in top layer, we see vertical movement down through the soil, which means there’s the potential to get into the environment – groundwater or surface water,” said Dana Kolpin, a research hydrologist for the U.S. Geological Survey.
USGS researchers tested an eastern Colorado wheat field that used treated sludge from a Denver sewage treatment plant. Chemicals in antibacterial soaps, cleaners, cosmetics, fragrances and prescription drugs such as Prozac and Warfarin not only persisted in the topsoil, but migrated down.
The researchers looked for 57 “emerging” contaminants that are increasingly showing up in the environment. Ten were detected in the soil at depths between 7 and 50 inches 18 months after the treated sludge was applied. None was in the field’s soil beforehand.
Called biosolids, about half of treated sewage sludge – about 7 million dry tons per year – from U.S. wastewater plants is applied to farm fields because the nutrients and organic matter help plants grow. The municipal sewage has gone through mandatory primary treatment and other processes that reduce pathogens but do not remove chemicals.