Risk Management and Trace Organic Compounds in Land-Applied Biosolids

The presence of trace organic compounds in municipal biosolids destined for land application has been well documented, including by a number of WERF studies and the 2009 U.S. EPA Targeted National Sewage Sludge Survey. Risk assessments are needed to determine whether there is any significance in the levels of trace organic chemicals found in biosolids-amended soils. In a significant first step toward answering this question, WERF has developed the State-of-the-Science Review of Occurrence and Physical, Chemical and Biological Processes Affecting Biosolids-Borne Trace Organic Chemicals in Soils (SRSK5T09) which identifies gaps in the data needed to evaluate the human and ecological exposure to trace organics in biosolids-amended soils.

Researchers for the project evaluated trace organics found in biosolids, determined the chemicals of greatest interest in the terrestrial environment, and then categorized them as high or low priority. The team based its assessment on occurrence data and readily available information on basic properties such as bioaccumulation and toxicity. An evaluation of applicable quantitative risk assessments was also conducted to identify the most important parameters for conducting ecological risk assessments and the techniques for obtaining the input parameter values. Based on the review, the research team felt it had identified data gaps for the parameters most important for conducting terrestrial risk assessments.

The report will help set the direction for WERF’s pending research challenge (currently under exploration), Trace Organics in Biosolids. The goal of the challenge is to further define the sources, fate, and transport of trace organics in biosolids as a means of supporting needed risk assessments. The products of this research will be used by WERF subscribers and other practitioners to make more informed risk management decisions concerning land application of biosolids.

Sept. 22, 2010