Toxic Substances Hydrology Program
Detergents in Streams May Just Disappear
The Story of 4-n-nonylphenol Biodegradation in Stream Sediments
Since about 2000, U.S. Geological Survey (USGS) scientists have been finding the chemical breakdown products (degradation products) of household detergents in streams downstream from wastewater treatment plants WWTPs. Detergent degradation products are among the most frequently detected compounds in stream samples and are among the compounds measured at the highest concentrations. Environmental professionals are concerned about these compounds because scientists have shown that a class of degradation products known as nonylphenols can disrupt normal hormonal (endocrine) function in fish. To help determine the environmental fate and transport of detergent degradation products discharged into streams from WWTPs, USGS scientists assessed the potential for naturally occurring microorganisms to remove one common detergent degradation product (4-n-nonylphenol) from stream sediments. This process of natural degradation by microorganisms is called biodegradation. In a laboratory setting the scientists tested the ability of 4-n-nonylphenol to biodegrade naturally in the environment using actual stream sediment from three streams. Sediments were collected from upstream and downstream of WWTP discharges. The experiments demonstrated that naturally occurring microorganisms that inhabit the stream sediments can biodegrade 4-n-nonylphenol in sediments under oxic (with oxygen) conditions in the laboratory; however, no biodegradation was observed in the laboratory under anoxic (without oxygen) conditions. These results help explain the presence and absence of these compounds in the environment, and may suggest ways to enhance natural removal mechanisms. For example, WWTP practices that produce high dissolved-oxygen concentrations in sediment and water downstream of wastewater discharges could improve the potential for natural removal. Environmental professionals, water resource managers, and WWTP managers can use this information to develop sound programs and practices regarding the occurrence of emerging wastewater contaminants in the environment.
Bradley, P.M., Barber, L.B., Kolpin, D.W., McMahon, P.B., and Chapelle, F.H., 2008, Potential for 4-n-nonylphenol biodegradation in stream sediments: Environmental Toxicology and Chemistry, v. 27, no. 2, p. 260-265, doi:10.1897/07-333.