AMSA SURVEYS OF DIOXIN-LIKE COMPOUNDS IN BIOSOLIDS

In October 2000, the Association of Metropolitan Sewerage Agencies (AMSA) began a voluntary survey to determine current levels of twenty-nine dioxin-like compounds in biosolids (sewage sludge). The twenty-nine dioxin-like compounds include seven polychlorinated dibenzo-p-dioxin, ten polychlorinated dibenzofurans, and twelve coplanar polychlorinated biphenyls (PCBs).These data were collected to assist the United States Environmental Protection Agency (USEPA) in developing an environmentally sound and technically correct dioxin limit for biosolids that are land-applied, and to determine whether concentrations of dioxin-like compounds in biosolids have decreased since AMSA's 1994/1995 Survey of Dioxin-like Compounds in Biosolids.Under the 2000/2001 survey, a total of 200 biosolids samples were submitted to Midwest Research Institute (MRI) for analysis. Cambridge Environmental Inc. reviewed the data and compared them to data obtained during AMSA's 1994/1995 survey.A review of the new data revealed that the dioxin concentrations of the 200 biosolids samples ranged from 7.1 to 256 parts per trillion (ppt) – toxicity equivalents (TEQ), with one “outlier” at 3,590 ppt-TEQ. The mean (average) concentration was 48.5 ppt-TEQ, while the median concentration was 21.7 ppt-TEQ. (These results are based on the non-detected dioxin-like compounds being set at one-half the detection limits.) In addition, a comparison of the data from the two surveys revealed that the average and median concentrations were substantially lower in AMSA's 2000/2001 survey.This paper presents data concerning the current levels of dioxin-like compounds in biosolids from the Publicly Owned Treatment Works (POTWs) that participated in the 2000/2001 survey, along with a comparison of the data obtained during AMSA's 1994/1995 and 2000/2001 surveys.