Accelerated Ultraviolet Treatment of Carbamazepine and NDMA in Water under 222 Nm Irradiation.

Krypton chloride (KrCl*) excimerultraviolet (UV) lightmay provideadvantages for contaminant degradation compared to conventional low-pressure(LP) UV. Direct and indirect photolysis as well as UV/hydrogen peroxide-drivenadvanced oxidation (AOP) of two chemical contaminants were investigatedin laboratory grade water (LGW) and treated secondary effluent (SE)for LPUV and filtered KrCl* excimer lamps emitting at 254 and 222nm, respectively. Carbamazepine (CBZ) and N-nitrosodimethylamine(NDMA) were chosen because of their unique molar absorption coefficientprofiles, quantum yields (QYs) at 254 nm, and reaction rate constantswith hydroxyl radical. Quantum yields and molar absorption coefficientsat 222 nm for both CBZ and NDMA were determined, with measured molarabsorption coefficients of 26 422 and 8170 M-1 cm(-1), respectively, and QYs of 1.95 x 10(-2) and 6.68 x 10(-1) mol Einstein(-1), respectively. The 222 nm irradiation of CBZ in SEimproved degradation compared to that in LGW, likely through promotionof in situ radical formation. AOP conditions improved degradationof CBZ in LGW for both UV LP and KrCl* sources but did not improveNDMA decay. In SE, photolysis of CBZ resulted in decay similar tothat of AOP, likely due to the in situ generation of radicals. Overall,the KrCl* 222 nm source significantly improves contaminant degradationcompared to that of 254 nm LPUV. The 222 nmphotolysis and advanced oxidation greatly improvethe degradation of carbamazepine and NDMA in water compared to thatof conventional 254 nm ultraviolet treatment.