Enhanced inactivation of Escherichia coli by ultrasound combined with peracetic acid during water disinfection

Peracetic acid (PAA) is a desirable disinfectant for municipal wastewater because of its potent disinfection performance and limited toxic by-products. This study explored the efficiency and mechanism of Escherichia coli inactivation by PAA combined with ultrasound simultaneously (ultrasound + PAA) or (ultrasound -> PAA) sequentially. The result showed that 60 kHz ultrasound combined with PAA sequentially (60 kHz -> PAA) had excellent inactivation performance on E. coli, up to 4.69-log(10). The result also showed that the increase of pH and humic acid concentration in solution significantly reduced the inactivation efficiency of 60 kHz -> PAA treatment. We also observed that the increase of temperature was beneficial to the disinfection, while anions (Cl-; HCO3-) had little effect. With 60 kHz -> PAA, the PAA and the synergism between PAA and ultrasound played major contribution to the inactivation, which we assumed might be due to both the diffusion of PAA into the cells and the damage to the cytomembrane by ultrasound, as evidenced through the laser confocal microscopy (LSCM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The inactivation mechanism involved the destruction of cell membrane and loss of intracellular material. Empirically, 60 kHz -> PAA was found to be effective for the inactivation of E. coli in actual wastewater, and the regrowth potential of E. coli treated by 60 kHz -> PAA was significantly lower than that treated only by PAA.

Automated summary

This study investigated the efficiency and mechanism of Escherichia coli inactivation by peracetic acid (PAA) combined with ultrasound simultaneously or sequentially. The results showed that sequential treatment of 60 kHz ultrasound followed by PAA had excellent inactivation performance on E. coli. The increase of pH and humic acid concentration in the solution significantly reduced the inactivation efficiency. The inactivation mechanism involved the destruction of cell membrane and loss of intracellular material.