Reduction of Pathogens in Biosolids in Mexico Using Solar Drying Beds

by Dominguez Sanchez, Teodulo.

In this study, die-off patterns of helminth ova, fecal coliforms, and Salmonella spp. in biosolids were documented using three small-scale sand drying beds located in a greenhouse. Treatments involved tilling the biosolids with differing frequencies. The results indicate that the inactivation rate for helminth ova was 0.88, 0.55, and 0.22 eggs/4 g TS day-1 for the intensively-tilled, moderately-tilled, and control beds, respectively. Achievement of Class A criteria was only possible in the intensively-tilled bed by Day 70 of the experiment. Salmonella spp. were inactivated to Class A levels in 9 days for the intensively and moderately-tilled beds. Regrowth of Salmonella spp. occurred thereafter in all beds, but high levels were seen only in the control bed. Fecal coliforms reached Class A criteria late in the experiment. Tilling treatments enhanced the inactivation rate of helminth ova and offer a potentially cost-effective method of pathogen reduction. 11