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Development of Microbial Assays for Municipal Sludge
Citation:
MECKES, M. C. Development of Microbial Assays for Municipal Sludge. In Proceedings, Disinfection 2009 Conference , Atlanta, GA, February 28 - March 03, 2009. Water Environment Federation, Alexandria, VA, Session 2, (2009).
Impact/Purpose:
To Share Information
Description:
Following a review of the Federal regulations and the supporting science for land application of municipal sludge, The National Research Council (NRC) recommended that the analytical methods used for determining the density of microorganisms in biosolids be validated by multi-lab testing. EPA=s sewage sludge regulations are designed to protect human health and the environment by requiring treatment of sewage sludge to reduce or eliminate pathogens when land-applied (40 CFR, Part 503, Subpart D). The regulations require that land-applied sewage sludge be treated to meet either Class A (pathogens reduced to below detectable levels) or Class B (treatments which reduce pathogen densities) requirements. Process monitoring includes analysis of biosolids (treated sewage sludge) for indicator bacteria such as fecal coliform or salmonellae in Class A biosolids, whereas fecal coliform monitoring may be used to demonstrate compliance for Class B biosolids. Current federal regulations (40 CFR, Part 503, Subpart D), specify that compliance monitoring be conducted in accordance with Standard Methods for the Examination of Water and Wastewater 18th edition. However, the analytical methods specified in that document were not developed for analysis of biosolids, and it does not specifically address analysis of biosolids for fecal coliforms or salmonellae. Consequently, analysts must adapt the published method to assay for these indicator organisms. The 2001 NRC report identified standardization and validation of methods for detection and enumeration of indicator organisms and specific pathogens as essential for oversight and compliance testing. As described in the April 9, 2003 notice, EPA agrees that pathogens deserve further attention. Pathogen projects relate back to Category D, Methods Development, and Category E, Pathogens, in the April 9, 2003 FR notice. See 68 FR 17388. EPA science has developed analytical protocols specifically designed for analysis of microorganisms in sewage sludge and biosolids. Multi-lab testing of these protocols provides performance standards which can be used for documenting the accuracy of these tests and ultimately the effectiveness of biosolids treatment processes.
