Inactivation mechanism of pathogenic bacteria using lime and ash in composting toilet

A composting toilet, using charcoal and rice husk as matrixes, requires inactivation treatment against pathogenic microorganisms derived from human feces before agricultural reuse. High pH conditions by adding calcium oxide (CaO) and wood ash is effective for lethal inactivation of pathogenic bacteria. However, quantitative information about application is limited. Therefore this study investigated the relationship between applied amount of these and compost pH. And then, inactivation rate and damage parts of Escherichia coli in several alkaline level of compost were observed with three different media. Moreover the infection risk by using CaO was assessed on the assumption that four member family infected salmonella used a composting toilet. CaO application can increased the compost pH and it promoted inactivation of pathogenic bacteria to induce damages of outer membrane and enzyme activities in both matrixes. This application can cause the damages of nucleic acid and/or metabolism with the pH increase. Wood ash can cause damage to enzyme activity significantly but much more applied amount wsas required than CaO. By dosing 900 g of CaO and reacting four hours, it will enable to decrease the annual acceptable infection risk to 10 -4 in both matrixes.