Activation of PMS by pipe corrosion products for fungi disinfection in water: Performance and mechanisms

Since the transportation of groundwater source to the waterworks last for dozens of hours, fungal spores present in the water can germinate and lead to microbial contamination. The main purpose of this paper is to inactivate fungi through the addition of peroxymonosulfate (PMS) activated by the pipe corrosion products (PCPs) during pipeline transportation or cleaning. MnO2, alpha-FeOOH, gamma-FeOOH and CuO are the main PCPs components, and they were chosen to activate PMS for fungal inactivation (Trichoderma harzianum, Aspergillus niger, Penicillium polonicum, and Cladosporium cladosporioides). There are two distinct stages in fungal inactivation: a lag phase and a following rapid decay. Of the fungi, Trichoderma harzianum exhibited high resistance to inactivation, while the others were completely killed under the same conditions. The ability of the four PCPs to activate PMS on fungal inactivation are as follows: CuO > alpha-FeOOH > gamma-FeOOH > MnO2. An inactivation experiment on E. coli as representative bacteria by PMS/PCPs was also carried out, and more than 5-log cell loss was obtained in 2 h. The efficiency of fungal inactivation was improved with an increase in the PMS and PCPs dosages while a lower pH and HA dose promoted the inactivation rate constants (k) conversely. Furthermore, the active species responsible for fungal inactivation were identified as the following, O-2(center dot-) > SO4 center dot- > center dot OH, based on indirect quenching tests and direct in-situ electron paramagnetic resonance (EPR) tests. After four times of recycling, the performance of the four PCPs remained almost stable. Likewise, a small decline of the k value was observed in actual groundwater experiments. Consequently, the PMS/PCPs system proposed in this paper provides a promising method for the control of fungi.