U.S. Department of the Interior | U.S. Geological Survey


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

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

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.

Additional background studies
Survey of Organic Wastewater Contaminants in Biosolids Destined for Land Application.


For more information contact Ed Furlong, USGS, at [email protected] or
303-236-3941, and Chad Kinney, Eastern Washington University, at
[email protected] or 509-359-7932. SETAC presentation is on Thursday,
Nov. 9, 4:10 p.m., Room 516 AB, Palais de Congrès.