Demonstration of a Process to Further Reduce Pathogens in Biosolids: Wenatchee Biosolids Treatment Method

The purpose of the study was to demonstrate that the Wenatchee Biosolids Treatment Method efficiently and effectively produces Class A biosolids for approval as an equivalent site-specific Process to Further Reduce Pathogens. The field experiment was started on May 9, 2011 and completed on June 13, 2011. Five test areas were set up in one of the drying beds and the biosolids were seeded with helminth ova and vaccine strain poliovirus. On May 9th, June 6th, and June 13th, samples were collected from the seeded areas for enteric viruses and helminth ova analysis. Weekly samples were collected from the five seeded areas and four control areas and tested for fecal coliform, total solids, volatile solids and pH. The initial fecal coliform concentrations ranged from 530,000 mpn/g to 81,500 mpn/g. By the fifth week, fecal coliform concentrations in the test areas and the control areas were all less than 1,000 mpn/g. Initial spiked poliovirus concentrations ranged from 60,000 pfu/4 g to 80,000 pfu/4g. Initial spiked helminth ova (Ascaris) concentration was several hundred ova per sample site. As of this writing, analyses for the samples collected through the end of the treatment period were under analysis and the results will be presented.