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The District submitted a proposal to the United States Environmental Protection Agency's (USEPA) Pathogen Equivalency Committee (PEC) in 1994 to conduct a full-scale study with a codified operation of its SPTs. After about four years at the end of the study, it was concluded that all batches of the final air-dried sludge product complied with the Class A criteria as specified by USEPA in the Part 503 Sewage Sludge Regulations from this optimized and codified operation study. Encouraged by this important conclusion, the District submitted its final report on the study in 1998 to the USEPA's PEC for obtaining certification of its SPTs as equivalent to PFRP. Subsequent to this study, an additional 166 final air-dried biosolids samples were analyzed from the District's SPTs from 1997 through 2001, and all of these samples also complied with Class A criteria.

Initially, although the District submitted approximately four years of data from a full-scale study, which showed that all batches of biosolids produced at the District's facilities were of Class A quality, the PEC had still issues that it wanted the District to resolve. These were with regard to the validity of the analytical methods used for pathogen analyses and proof that the District's SPTs had the ability to achieve a two-log reduction of Ascaris ova and three-log reduction of enteric viruses. The District did address these two issues in its report as well as in two articles published in Water Environment Research in 2000. Yet, the PEC was still not convinced. Subsequently, the District validated the analytical methods that it used in its study against the methods recently published by the PEC, and demonstrated by an alternative method that its SPTs had the intrinsic ability to achieve the Ascaris ova and enteric virus log reductions mentioned above. Also, the District regularly met with the USEPA Region 5 Biosolids Coordinator to inform and discuss the progress and results of the study as well as the outcome of the correspondence and discussions that the District staff had with the PEC. We believe that the diligent efforts made by the District in conducting a detailed and controlled study made over a period of four years to show that all the batches of biosolids produced during this period complied with the Class A criteria, elaborate and discussions made with the Chairman and other members of the PEC, and keeping the USEPA Region 5's Biosolids Coordinator regularly informed about the progress of the work performed have resulted in the issue of a conditional site-specific PFRP certification for two years to the District's SPTs by the USEPA Region 5.

The District will benefit from the PFRP certification by a significant reduction in the number of biosolids samples to be analyzed, and hence will realize a significant savings in the cost of analysis. Also, the site-specific certification will give the needed flexibility to the operations department to program their biosolids distribution to various end users without waiting for the analytical results.
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Document Type: Research Article

Publication date: 2003-01-01

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