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Water: Biosolids

Biosolids: Targeted National Sewage Sludge Survey Report

Fact Sheet; January 2009; EPA 822-F-08-006

EPA is releasing the results of the Targeted National Sewage Sludge Survey (TNSSS). The survey measured concentrations for a target list of chemicals (analytes) in sewage sludge from a statistically derived sample of publicly-owned treatment works (POTWs) in the contiguous United States with flow rates of at least one million gallons per day and which use secondary treatment or better.

The TNSSS Overview Report provides an overview of two reports that together comprise the TNSSS:

  1. Targeted National Sewage Sludge Survey Sampling and Analysis Technical Report ("Technical Report"), and
  2. Targeted National Sewage Sludge Survey Statistical Analysis Report ("Statistical Report").

The Overview Report provides summary information on the background of the survey, the selection of chemicals and POTWs included in the survey, and some preliminary observations based on survey results. Additional details may be found in the Technical and Statistical Reports. Results from the TNSSS provide important chemical concentration information that EPA intends to use in its effort to evaluate biosolids generated by the nation's POTWs.

About the Survey

We are working to understand potential pollutants in sewage sludge and in the environment. Because many chemicals tend to accumulate in sewage sludge during wastewater treatment, EPA initiated the TNSSS to characterize what chemicals may be present in sewage sludge. The survey included metals, inorganic ions, and certain organics, such as polycyclic aromatic hydrocarbons, semivolatiles, polybrominated diphenyl ethers, pharmaceuticals, steroids and hormones.

EPA collected and analyzed sewage sludge samples from 74 POTWs that employ secondary treatment or better. The 74 POTWs statistically represent over 3,300 of the nation's largest POTWs. Sample collection at the 74 POTWs was conducted between August 2006 and March 2007.

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Results include minimum and maximum concentrations for 145 different analytes, including four anions (nitrite/nitrate, fluoride, water extractable phosphorus), 28 metals, four polycyclic aromatic hydrocarbons, two semivolatile chemicals, 11 PBDEs, 72 pharmaceuticals, and 25 steroids and hormones.

Results also include nationally-representative estimates of the underlying distribution of concentrations across POTWs as well as an in-depth statistical analysis of a subset of 34 out of the 145 analytes. EPA selected the subset of 34 analytes for in-depth statistical analysis. These 34 analytes were selected for the following reasons:

  • nine "target" analytes from the 2003 Biennial Review were identified as needing additional evaluation of potential risks using more up-to-date sludge concentration and occurrence data;
  • molybdenum is being re-evaluated using updated information to determine the need for a revised numeric standard in land applied biosolids;
  • four PBDEs have been detected in various environmental media and acceptable human health benchmarks exist that may be useful for any future risk assessment purposes; and
  • 20 pharmaceuticals were detected at 90 percent or more of the POTWs in the target population.

Briefly, the survey found that:

  • Nitrite/nitrate, fluoride and water-extractable phosphorus were found in every sample.
  • 27 metals were found in virtually every sample, with one metal (antimony) found in no less than 72 samples.
  • Of the six semivolatile organics and polycyclic aromatic hydrocarbons, four were found in at least 72 samples, one was found in 63 samples, and one was found in 39 samples.
  • Of the 72 pharmaceuticals, three (i.e., cyprofloxacin, diphenhydramine, and triclocarban) were found in all 84 samples and nine were found in at least 80 of the samples. However, 15 pharmaceuticals were not found in any sample and 29 were found in fewer than three samples.
  • Of the 25 steroids and hormones, three steroids (i.e., campesterol, cholestanol, and coprostanol) were found in all 84 samples and six steroids were found in at least 80 of the samples. One hormone (i.e., 17a-ethynyl estradiol) was not found in any sample and five hormones were found in fewer than six samples.
  • All of the flame retardants except one (BDE-138) were found in nearly every sample; BDE-138 was found in 56 out of 84 samples.

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Next Steps

We plan to evaluate the pollutants identified by the survey as being present in sewage sludge. As its first priority, using the survey information, EPA has begun assessing molybdenum and the nine pollutants identified from the 2003 biennial review as needing updated concentration information to determine whether additional action may be necessary. In addition to the survey information, EPA will evaluate other available data and conduct exposure and hazard assessments for these pollutants if sufficient data are available. Later this year, EPA expects to initiate evaluations of other pollutants in the survey that may warrant further consideration. The evaluations will depend on the availability of data needed to conduct the evaluations.

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Additional Information

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

To get more information about the TNSSS, please contact Rick Stevens (stevens.rick@epa.gov) at (202) 566-1135.

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