Effect of Heating Patterns on Inactivation and Regrowth Potential of Bacterial Indicator Organisms in Simulation of Composting

Treatment of sewage sludge by composting for the production of materials useful as a soil amendment is a feasible method of achieving both waste disposal and agricultural enhancement simultaneously。 However, the hygienic safety of the final products is an issue which requires resolution. This study was an investigation of the effects of heating patterns on the inactivation and regrowth potential of Salmonella, Escherichia coli, and Faecal streptococcus. A laboratory thermal controller was used to apply three patterns of heating;namely, single-impact, constant, anαintermittent. Single-impact heating showed the greatest effect on inactivation and intermittent heating had the least effect. Also, the organisms subjected to single-impact heating had the least regrowth potential while those subjected to intermittent heating had the greatest potential. The addition of inorganic suspended solids(kaolin)and dissolved organic matter severely inhibited the inactivation of all the organisms.