Application of Nitrate-Nitrite and Atrazine Actinometry for Determination of UV Fluence in Drinking Water and Reuse Applications

摘要

The use of nitrate-nitrite as a chemical actinometer for the determination of UV fluence duringrndrinking water treatment has recently been reported. In wastewater treatment, UV radiation is used forrndisinfection as well as for destruction of trace organic compounds susceptible to direct photolysis, suchrnas N-Nitrosodimethylamine. A common measure of UV radiation is expressed as fluence in units ofrnmJ/cm~2, which may be difficult to measure in pilot-scale or full-scale UV reactors, where spiking arnchemical at sufficient concentration prior to UV treatment is impractical. Actinometry provides a directrnmeasure of UV fluence without knowledge of precise geometrical configuration of the UV reactor.rnNitrate ion is also commonly present in reclaimed waters, allowing the determination of UV fluence.rnAtrazine, a well characterized actinometer may also be present in reclaimed waters and provide anrnalternative to the nitrate system. This study compared the measurements of UV fluence by nitrate-nitrite,rnatrazine, and radiometry in natural and reclaimed waters. The formation pathway of nitrite during UVrnexposure of nitrate ion is complex and can depend on various water quality parameters, such as dissolvedrnorganic matter (DOM) concentration and other constituents that react with intermediate radicalsrnproduced during photolysis of nitrate. In this study we examined the effects of DOM on the nitrite yieldrnand discuss its practical uses for determination of UV fluence at disinfection and advanced oxidationrndoses. Our preliminary experiments show an enhanced nitrite yield in reclaimed waters where DOM isrntypically at higher concentration, which indicates that nitrate should be used with caution forrndetermination of UV fluence. The effects of DOM on atrazine photolysis were negligible as compared tornthe nitrate system and atrazine provides a more robust alternative for determination of various UVrnfluence in reclaimed water treatment.