High potential of the vacuum UV-activated peracetic acid (VUV/PAA) process in eliminating recalcitrant contaminants and waterborne pathogens: Assessing the efficacy of annular and helical reactor configurations

The effectiveness of VUV/PAA in degrading Ciprofloxacin (CIP) and inactivating E. coli was studied. VUV was more efficient than UVC in activating PAA. The VUV/PAA process degraded CIP twice as fast as the VUV process under similar conditions and was more effective in acidic or neutral solutions than in alkaline solutions. The hydroxyl radicals formed were key to the degradation, whereas the R-C species played a lesser role. Furthermore, the VUV/PAA process achieved a satisfactory CIP degradation rate in spiked tap water. Operating the reactors in batch mode, completely degraded CIP in 30 min, and 86.5 % TOC removal was achieved in 120 min of a 40 mg/L CIP solution. In addition, VUV/PAA inactivated a 6.5-log of 1.2 × 109 CFU/mL of E. coli in only 5 min. Moreover, the VUV/PAA process was compared in a helical (HPR) and annular photoreactor (APR); the HPR led to approx. x3 higher ▪OH generation and superior CIP degradation rate. The VUV/PAA process improved CIP degradation in both the APR and HPR with longer hydraulic residence times, where the HPR outperformed the APR in degrading CIP. Overall, the VUV/PAA@HPR system is an effective method for enhancing the degradation of recalcitrant organics and waterborne pathogens in contaminated water, including in the flow-through mode, making it a promising process for water treatment.