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 × 105 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 •OH reactivity (k > 5 × 109 M−1 s−1), except musk ketone (MK) (k = 2.3 × 109 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 gO3/gDOC. The elimination levels of the other synthetic musks were below 50% at 0.5 gO3/gDOC. The fluence-based UV photolysis rate constant of the synthetic musks was determined to be (0.2 – 2.7) × 10−3 cm2/mJ. The elimination levels of synthetic musks during UV alone treatment ranged from 7 to 81% at a UV fluence of 500 mJ/cm2. The addition of 10 mg/L H2O2 (UV/H2O2) significantly enhanced the elimination of most synthetic musks (achieving >90% elimination at 500 mJ/cm2), indicating that the •OH reaction was mainly responsible for their elimination. The addition of 10 mg/L FAC (UV/FAC) also significantly enhanced the elimination of olefinic and aromatic synthetic musks (>90%), for which the reaction with ClO• 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 •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.