Rapid oxidation of emerging contaminants by far-UVC/chlorine system: Energy efficiency and synergistic mechanism

Emerging contaminants (ECs) have received widespread attention. In this study, the Far-UVC (222 nm) combined with chlorine (UV 222 /chlorine) system is used to remove ECs from water. The results reveal that carbamazepine (CBZ) was effectively degraded by the UV 222 /chlorine system, with a degradation efficiency of 92.5 % within 45 min at a UV fluence of 666 mJ cm −2 and a chlorine concentration of 200 μM. Quenching experiments indicate that HO• and Cl• play a major role in the UV 222 /chlorine system. The steady-state concentrations of HO• (3.85 × 10 −14  M), Cl• (8.55 × 10 −14  M), and ClO• (9.13 × 10 −12  M) in the UV 222 /chlorine system is determined by using probe method. The degradation of CBZ by UV 222 /chlorine system (92.5 %) is significantly better than that of UV 222 alone (32.3 %) and the UV 254 /chlorine system (78.3 %) at the same UV dose. In addition, the UV 222 /chlorine system exhibits excellent EE/O performance of 0.53 KWh/L, effectively reducing resource consumption. Compared with the UV 222 /peracetic acid (PAA) system, the UV 222 /chlorine system shows higher degradation efficiency for CBZ in a wide pH range of 4 to 9. In addition, the presence of Cl − and HCO 3 − shows no significant impact on both the UV 222 /chlorine and UV 222 /PAA systems. The UV 222 /chlorine system is expected to become a promising alternative to traditional UV and chlorine disinfection techniques in water treatment . This study provides technical support for promoting the practical application of the UV 222 /chlorine system.