Inactivation of fungal spores in water with peracetic acid: Efficiency and mechanism

In recent years, peracetic acid (PAA) has been widely used in sewage disinfection due to its strongly sterilizing capacity and less toxic by-products production. However, there was no studies on the inactivation kinetics and mechanism of fungal spores in water by PAA as well as their regrowth. The inactivation efficiency and mechanism of Aspergillus niger and Aspergillus flavus by PAA was illustrated in this study. The results showed that the inactivation of fungal spores fitted to the delayed Chick-Watson model well. The inactivation rate constants were 0.038 and 0.033 L mg-1 min-1, respectively. The effects of pH value and humic acid concentration on the inactivation efficiency were negative and the effect of temperature was positive, while the effect of HCO3- and Cl- on the disinfection of fungal spores could be negligible. The results of flow cytometric measurements, morphological observation and the leakage of intracellular substances indicated that the inactivation of fungi by PAA was attributed to the penetration of cell membranes rather than the damage of cell membranes. PAA was found to be effective for the inactivation of fungal spores, but was less effective than several traditional disinfectants (Cl2, ClO2) under the same condition. Furthermore, the regrowth of fungal spores after disinfection with PAA was also evaluated. The regrowth of fungal spores that after 1-3 log inactivated in the R2A medium within 5 days was observed, but the regrowth of completely inactivated fungal spores in R2A and in trace element solution was negligible. This study provides the valuable information for the application of PAA in the control of fungal pollution.