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>Experimental and model comparisons of low- and medium-pressure Hg lamps for the direct and H{sub}2O{sub}2 assisted UV photodegradation of N-nitrosodimethylamine in simulated drinking water
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Experimental and model comparisons of low- and medium-pressure Hg lamps for the direct and H{sub}2O{sub}2 assisted UV photodegradation of N-nitrosodimethylamine in simulated drinking water
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机译：Experimental and model comparisons of low- and medium-pressure Hg lamps for the direct and H{sub}2O{sub}2 assisted UV photodegradation of N-nitrosodimethylamine in simulated drinking water
Both low- and medium-pressure Hg lamps (LP and MP, respectively) were used as ultraviolet light (UV) sources to destroy N-nitrosodimethylamine in a synthetic "natural" water. The lamp performances were directly compared via the UV fluence-based rate constants, which demonstrates that LP and MP have virtually identical photonic efficiencies (fluence-based rate constants of 2.29E-3 and 2.35E-3 cm{sup}2/ mJ, respectively). This indicates that the quantum yield for NDMA photolysis is independent of wavelength in the UVC region: a value of 0.30 molleinstein is found at pH 8.1. Addition of 100 mg/L of H{sub}2O{sub}2 leads to a 30 increase in the LP fluence-based rate constant but does not alter the MP rate constant, likely due to the tradeoff between light screening by H{sub}2O{sub}2 and additional radical based degradation. However, in terms of the time-based rate constant, this level of H{sub}2O{sub}2 slightly enhances the LP performance but hinders the MP performance, suggesting that H{sub}2O{sub}2 is of little or no economic benefit for NDMA removal by UV. All these effects are explained by modeling the photochemistry according to standard equations. The model predicts that H{sub}2O{sub}2 may enhance NDMA removal for short optical path lengths but that light-screening by H{sub}2O{sub}2 may decrease the removal rates for optical path lengths typical of those found in UV reactors.
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