Inactivation Kinetics of Indicator Microorganisms during Solar Heat Treatment for Sanitizing Compost from Composting Toilet

抄録

This study aimed to estimate the sanitization effectiveness of compost by solar heating. Compost produced from composting toilet was inoculated with Escherichia coli, Enterococcus faecalis and Ascaris eggs and subjected to solar heating. The heating was performed by direct exposure of compost to sun and in a solar box. From treated compost, the number of isolated bacteria was determined by plating method and the number of Ascaris eggs was determined by microscopy counting. The inactivation kinetics of microorganisms were modeled using nonlinear regression software tool. The result showed that the temperature regime produced by direct sunlight and solar box during heating were categorized as mesophilic (> 30°C) and pasteurization (> 70°C), respectively. The log reduction of microorganisms in heated compost by solar box was significantly higher than that of direct sunlight. The inactivation rate was slow in compost heated by the sun but fast in compost heated by solar box. Escherichia coli appears to be the most sensitive to destruction temperatures achieved by solar heating. The thermal decimal decay occurred rapidly in solar box while it was prolonged with the direct sunlight. The high and uniform temperature distribution obtained with solar box during heating proved to be an efficient option for safe use of compost.