Sporocidal properties of peracetic acid and hydrogen peroxide, alone and in combination, in comparison with chlorine and formaldehyde for ultrafiltration membrane disinfection
Résumé
The sporocidal properties of peracetic acid, hydrogen peroxide, chlorine, and formaldehyde were compared in vitro using a dilutionneutralization micromethod. A combination of peracetic acid and hydrogen peroxide was also tested to assess their interactions. The activities of these agents, which are widely used as disinfectants, were evaluated against Bacillus spore isolates found on stored membranes and collection cultures. Peracetic acid and chlorine exhibited an excellent antimicrobial activity, with a destruction of 105 spores/mL after 5min of contact. Generally the effects of the biocides tested were time dependent. The sporocidal activities of hydrogen peroxide and formaldehyde were the lowest. The combination of peracetic acid and hydrogen peroxide, tested by a checkerboard micromethod, was found to be synergistic. The minimal sporocidal concentration (MSC) was established in terms of time for each biocide. The lowest MSC values for peracetic acid, hydrogen peroxide, chlorine, and formaldehyde were 168336ppm (12h of contact), 562511250ppm (57h), 168336ppm (23h), and 18753750ppm (530min), respectively. The MSC of a biocide combination of peracetic acid and hydrogen peroxide showed that synergy was maintained with increasing contact time and that the MSC could be reduced by two to eight times when compared with those of the biocides alone. Optimal concentrations and contact times of those chemicals that were promising in vitro were then tested for their ability to disinfect ultrafiltration membranes. The sporocidal activities of peroxide compounds and chlorine were confirmed and the synergism between peracetic acid and hydrogen peroxide was also maintained. The biocide combination of peracetic acid and hydrogen peroxide gave successful results; 21ppm of peracetic acid + 2813ppm of hydrogen peroxide allowed a total disinfection of hollow fibers in 23h of contact
Les proprits sporocides de l'acide peractique, du peroxyde d'hydrogne, du chlore et de la formaldhyde ont t compares in vitro par une micromthode de dilutionneutralisation. Les interactions entre l'acide peractique et le peroxyde d'hydrogne ont aussi t values en combinant ces deux composs. L'activit de ces agents largement utiliss comme dsinfectants a t value sur des spores de Bacillus isoles de membranes entreposes et de cultures de collection. L'acide peractique et le chlore possdent une excellente activit antimicrobienne avec une destruction de 105 spores/mL aprs un temps de contact de 5min. En gnral, l'effet de ces biocides est temps dpendent. Le peroxyde d'hydrogne et la formaldhyde possdent les plus faibles activits sporocides. La combinaison acide peractique et peroxyde d'hydrogne, vrifie par une micromthode de l'chiquier, s'est avre synergique. La concentration minimale sporocide (CMS) de chacun des biocides a t value en fonction du temps. Les plus faibles CMS pour l'acide peractique, le peroxyde d'hydrogne, le chlore et la formaldhyde taient de 168336ppm (1 2h de contact), 5625 11250ppm (5 7h), 168336ppm (2 3h) et 18753750ppm (5 30min), respectivement. La CMS d'un mlange d'acide peractique et de peroxyde d'hydrogne indique que la synergie se maintient avec la prolongation du temps de contact, ce qui peut rduire de 2 8 fois la CMS obtenue avec le biocide seul. Ces agents chimiques prometteurs in vitro ont t vrifis leur concentration optimale et leur temps de contact optimal pour leur capacit dsinfecter des membranes ultrafiltrantes. L'activit sporocide du peroxyde et du chlore s'est confirme de mme que la synergie entre l'acide peractique et le peroxyde d'hydrogne. La combinaison acide peractique et peroxyde d'hydrogne a donn de bons rsultats : 21ppm d'acide peractique + 2813ppm de peroxyde d'hydrogne permettent une dsinfection complte des fibres profondes aprs 23h de contact.