Low-dose H2O2 enhances taste and odor compound removal and DBP control in UV/chlorine process

Ultraviolet/chlorine (UV/Cl 2 ) process is promising for degrading persistent micropollutants, but suffers from toxic disinfection by-products (DBPs) formation. Here, we developed a new UV/Cl 2 /H 2 O 2 process by combining UV/Cl 2 with a low dosage of H 2 O 2 , which not only enhanced micropollutant degradation but also reduced DBP formation. Taking a recalcitrant taste and odor (T&O) compound, 2,4,6-tribromoanisole (TBA) as an example. UV/Cl 2 /H 2 O 2 increased 2,4,6-TBA degradation rate constants by 90 % and 60 % than those of UV/H 2 O 2 and UV/Cl 2 , respectively, primarily due to increased HO • production. The combined contribution of UV and HO • to the degradation was substantial, accounting for 82−96 % of the overall degradation. Regarding simultaneous DBP formation from 2,4,6-TBA, UV/Cl 2 /H 2 O 2 decreased trihalomethanes (THMs) levels by 79 % compared to UV/Cl 2 . Furthermore, during post-chlorination, UV/Cl 2 /H 2 O 2 reduced the DBP formation potential by 18 % compared to UV/Cl 2 . In UV/Cl 2 /H 2 O 2 , THMs formation was reduced by 52.5 %, haloacetamides (HAMs) formation by 48.5 %, and haloacetic acids (HAAs) formation by 16.7 % compared to UV/Cl 2 using real water samples. The reduced DBP formation may result from the competitive reaction of HO • with halogenation agents and the destruction of halogenated sites. This work establishes a practical AOP that simultaneously enhances micropollutant removal and suppresses DBP formation.