Elimination efficiency of synthetic musks during the treatment of drinking water with ozonation and UV-based advanced oxidation processes

Abstract

This study investigated the reaction kinetics and elimination efficiency of eleven synthetic musks during ozonation and UV254nm-based, advanced oxidation processes. The synthetic musks containing olefin moieties with electron-donating alkyl substituents such as octahydro tetramethyl naphthalenyl ethanone (OTNE) and ambrettolide (AMBT) showed high reactivity toward ozone (k >= 3.7 x 10(5) M-1 s(-1)) and free available chlorine (FAC) (k = 9.2 - 88 M-1 s(-1)), while all other synthetic musks were less ozone reactive (k = 0.3 - 560 M-1 s(-1)) and FAC-refractory. All synthetic musks showed high center dot OH reactivity (k > 5 x 10(9) M-1 s(-1)), except musk ketone (MK) (k = 2.3 x 10(9) M-1 s(-1)). In concordance with the kinetic information, OTNE and AMBT were efficiently eliminated (> 97%) in simulated ozone treatments of drinking water at a specific ozone dose of 0.5 gO(3)/gDOC. The elimination levels of the other synthetic musks were below 50% at 0.5 gO(3)/gDOC. The fluence-based UV photolysis rate constant of the synthetic musks was determined to be (0.2 - 2.7) x 10(-3) cm(2)/mJ. The elimination levels of synthetic musks during UV alone treatment ranged from 7 to 81% at a UV fluence of 500 mJ/cm(2). The addition of 10 mg/L H2O2 (UV/H2O2) significantly enhanced the elimination of most synthetic musks (achieving > 90% elimination at 500 mJ/cm(2)), indicating that the center dot OH reaction was mainly responsible for their elimination. The addition of 10 mg/L FAC (UV/FAC) also signifi-cantly enhanced the elimination of olefinic and aromatic synthetic musks (> 90%), for which the reaction with ClO center dot was mainly responsible. For MK and two alkyl synthetic musks, their elimination during UV/FAC treatment was still limited (28 - 64%) and was mainly achieved by UV photolysis or reaction with center dot OH. In summary, this study substantiates the chemical kinetics approach as a helpful tool for predicting or interpreting the elimination of micropollutants during oxidative water treatment.