Interlaboratory Validation of USEPA Method 1680: Fecal Coliforms in Biosolids by Multiple-Tube Fermentation Procedures

In the United States, the use and disposal of biosolids (including domestic septage) are regulated under 40 CFR Part 503. Subpart D of this regulation protects public health and the environment through requirements designed to reduce the potential for contact with pathogens in biosolids applied to land or placed in a surface disposal site. Biosolids cannot be applied to land or placed on a surface disposal site unless they have met the requirements to ensure reduction of pathogens which are divided into two categories: Class A and Class B. The goal of the Class A requirements is to reduce the pathogens (including enteric viruses, pathogenic bacteria, and viable helminth ova) to below detectable levels. The goal of the Class B requirements is to ensure that pathogens have been reduced to levels that are unlikely to have a threat to public health and the environment under the specific use conditions.The 503 regulations require evaluation of one indicator, the fecal coliform group, and three pathogens: Salmonella, enteric viruses, and viable helminth ova. Although the regulation stipulates methods required to evaluate the concentration of each organism, none of the methods had undergone validation at the time of the regulation notice. USEPA Method 1680 for the enumeration of fecal coliforms in biosolids was submitted to a single-laboratory validation, and is currently undergoing interlaboratory validation at 12 laboratories familiar with the analysis of biosolids. Results of the interlaboratory validation of USEPA Method 1680 will be the primary focus of the presentation.