Inactivation mechanisms of pathogenic bacteria in several matrixes during the composting process in a composting toilet

Abstract

This study aimed to compare the inactivation rate and the mechanisms of pathogenic bacteria in three matrixes (sawdust, rice husk and charcoal) during the composting process. The inactivation rate was evaluated with Escherichia coli strain and the damaged parts and/or functions were evaluated with three different media. Normalized inactivation rate constant in three media and from three matrixes had no significant difference in each process (pure, 1 month and 2 months). The value in rice husk was relatively increased during 2 months but there was no significant difference. The inactivation rate constants of Tryptic Soy Agar (TSA) and Compact Dry E. coli/Coliform in pure sawdust and rice husk were relatively lower than that of Desoxycholate Agar, but increased in 2 months. This indicated that damaging part was changed from outer membrane to enzymes and metabolisms during the 2-month composting process. In the case of charcoal, only the TSA value in apure matrix was relatively lower than that of others, but it increased in 2 months. This indicated that damaging part was changed from outer membrane and enzyme to metabolisms during the composting process. Composting matrix and composting process did not significantly affect inactivation rate of pathogenic bacteria during the process but affected the damaging part of the bacteria.

Toilet compost and human urine used in agriculture: fertilizer value assessment and effect on cultivated soil properties

“…This TC is characterized by a mixed matter of faeces and a matrix which can be sawdust or charcoal. [11,12] TC is mainly used as a soil conditioner. However, amendment of TC slowly releases mineral fertilizers (organically bounded) and then represents a good combination with urine amendment.…”

Composting and Dry Desiccating Toilets (Latrines)

“…In that study, the sawdust had a lower pH (5.5) than the charcoal ash (12.5) (Niwagaba et al, 2009). Sossou et al (2014) suggested that rice husk charcoal ash may be a more effective desiccant in supporting fundamental microorganism inactivation mechanisms than sawdust, rice husk, and charcoal. Rice husk and sawdust are also reported to damage the outer membrane of E. coli while ash inactivates by damaging the outer membrane and/or enzyme activity and, thus, may be more lethal (Sossou et al, 2014).…”

“…Common desiccants are ash (from burning wood or other materials), dry soil or sand, dry leaves, dry grass, rice husks, lime (quicklime or hydrated lime), crushed oyster shells, and shea nut shells. Selection of a desiccant is typically determined by what is locally and seasonally available and is cost effective (Mehl et al, 2011;Magri et al, 2013;Sossou et al, 2014).…”

“…Sossou et al (2014) suggested that rice husk charcoal ash may be a more effective desiccant in supporting fundamental microorganism inactivation mechanisms than sawdust, rice husk, and charcoal. Rice husk and sawdust are also reported to damage the outer membrane of E. coli while ash inactivates by damaging the outer membrane and/or enzyme activity and, thus, may be more lethal (Sossou et al, 2014). Similarly, Hijikata et al (2016) found that ash (wood, rice straw, and mix of ashes with oyster shell) and lime damage the outer membrane and enzyme activities of E. coli and in MS2 coliphage reduce infectivity.…”

Bactericidal and virucidal mechanisms in the alkaline disinfection of compost using calcium lime and ash

“…From a hygienic perspective, feces should always be considered to contain pathogens that cause gastrointestinal infections. Although the composting process in dry toilets reduces concentrations of indicator microorganisms and pathogens to some extent (Sossou et al, 2011;Sossou et al, 2014), the compost recovered from a dry toilet always has the potential to include pathogens derived from feces of infected persons, which pose infectious disease risks for users (Otaki et al, 2007). The highest infection risk most likely is posed during emptying the compost and exchanging the matrix (Nakagawa et al, 2006;Schönning et al, 2007).…”