Inactivation experiments50 mL of log phase E.coli stock was dosed into 10 L of DI water (Milli-Q water purification system, Millipore Synergy 185, US) to prepare thestock suspension. The initial concentration of E.coli in the stock suspensionwas 106–107 colony-forming unit (CFU) per mL with UVtransmittance to be 93.3 ± 0.1 % at 265 nm (UV transmittance wasmeasured by measured by DR6000 UV VIS Spectrophotometer, HACH,U.S.A.).After the disinfection, 500 mL of the stock suspension was collectedfor further analysis. Enumeration of E.coli was performed using thespread plate method. In brief, samples were serially diluted with phosphatebuffered saline (PBS, Sigma, USA) solution, plated in duplicate onTryptic Soy Agar (TSA, Sigma, USA) and incubated overnight at 37 ◦C.After incubation, the colonies on the plates were counted and the countswere averaged and recorded as CFU/mL.The bacteria removal performance was evaluated by plate countingas described above and was represented by log removal as shown in Eq.(1).