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

Abstract

In the present study, the bactericidal and virucidal mechanisms in the alkaline disinfection of compost with calcium lime and ash were investigated. Two indicator microorganisms, Escherichia coli and MS2 coliphage, were used as surrogates for enteric pathogens. The alkaline-treated compost with calcium oxide (CaO) or ash resulted primarily in damage to the outer membrane and enzyme activities of E. coli. The alkaline treatment of compost also led to the infectivity loss of the coliphage because of the partial capsid damage and RNA exteriorization due to a raised pH, which is proportional to the amount of alkaline agents added. These results indicate that the alkaline treatment of compost using calcium oxide and ash is effective and can contribute to the safe usage of compost from a mixing type dry toilet.

Disinfection Efficacy of Slightly Acidic Electrolyzed Water Combined with Chemical Treatments on Fresh Fruits at the Industrial Scale

“…The mean initial populations of TAB on the fresh apple, mandarin, and tomato fruits were 5.02, 4.72, and 5.98 log CFU/fruit, respectively. Treatment of CaO-FA+SAEW resulted in a higher reduction for microbial population of TAB on the surface of fruits when compared to the FA+SAEW; the results may be explained by the fact that CaO has a pH of about 12.5, which can be associated with antimicrobial activity by destroying the outer membrane and interfering in the microbial enzymatic activity [34]. In addition, it can control physiological disorders and remove residual pesticide and other debris during postharvest processing.…”

Assessment of recommended approaches for containment and safe handling of human excreta in emergency settings

“…OH - ions present in lime suspensions saponify lipids in the enveloping membrane [ 55 ], while the electronegativity of chlorine solutions has been shown to oxidise and denature bacterial cell wall proteins [ 56 ]. In contrast, for viruses (including phages) it is more difficult to elucidate the precise mechanism of removal and inactivation, but both chlorine and lime based approaches appear to inactivate viruses by reacting with viral proteins and genomic material [ 57 , 58 ].…”

Composting and Dry Desiccating Toilets (Latrines)

“…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.…”

“…carbon and hydroxides) of the material (Hijikata et al, 2016). Usually wood ash and ash produced at a higher burning temperature are preferable compared to ash from grass, rice, or mixed ash that have lower alkaline properties (Hijikata et al, 2016). Niwagaba et al (2009) detected E. coli in feces from urine diversion dry toilets with sawdust desiccant after two months but did not for those where wood ash was added and also found on average 2 log 10 higher concentrations of Enterococcus spp.…”