Wastewater Issues Get Wormy

Recent research indicates that earthworms may be an important initial step by which organic contaminants could enter the terrestrial food web. Wastewater treatment plants process millions of gallons of mixed solid and liquid human waste daily, returning treated effluent to surface and ground water and disposing of the residual sludge. Roughly half of the many thousands of dry tons of treated sludge (usually referred to as biosolids) generated annually in the U.S. are applied to agricultural soils as a nutrient-rich soil amendment. Recent USGS research has identified a wide variety of organic contaminants (such as disinfectants, pharmaceuticals, synthetic fragrances, and plasticizers) that can be present in biosolids, often in concentrations tens to thousands of times higher than found in treated liquid waste. One concern related to the practice of land application of biosolids is whether any of these organic contaminants find their way into soil-dwelling organisms. To address this concern, USGS and Eastern Washington University scientists collaborated on a study of earthworms collected from agricultural soils in the Midwest and Western United States that had been exposed to land-applied biosolids. The samples were analyzed for a diverse array of pharmaceuticals and other organic contaminants (77 target compounds were measured). Soil and earthworm samples were collected from select agricultural fields early and late in the growing season. Thirty-one compounds including triclosan (household disinfectant), several fragrances, caffeine, and fluoxetine (the antidepressant Prozac) were detected in earthworms from biosolid-applied fields, with tissue concentrations ranging from 100’s to 1000’s of micrograms per kilogram (parts per billion). These results demonstrate that earthworms can accumulate a range of these chemically diverse organic contaminants within their tissues, and may be an important initial step by which these compounds could enter the terrestrial food web. For more information contact Ed Furlong, USGS, at efurlong@usgs.gov or 303-236-3941, and Chad Kinney, Eastern Washington University, at ckinney@mail.ewu.edu or 509-359-7932.