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Ultraviolet (UV) treatment has been shown to produce a nearly undetectable level ofdisinfection byproducts (DBPs) at the doses commonly used. Most UV treatmentscenarios include either chlorination or chloramination for the purpose of maintaining adisinfectant residual during distribution. For this reason, there has also been an interest inimpacts UV treatment might have on natural organic matter (NOM) or DBP precursors.Several research groups have examined this question, and results to date have failed toshow a substantial effect at typical UV doses.The purpose of this research was to expand upon the prior work to include studiesof total organic halide (TOX) and to consider THM and HAA formation under shortincubation times. Raw waters from several chemically and geographically distinctsources were collected and treated with UV light (low pressure) and chlorine in theUMass laboratory. Care was taken to use realistic chlorine doses (2-6 mg/L) andcontrolled pH, along with medium to high UV doses (400-1500 mJ/cmsup2/sup).Results showed substantial increases in rate of formation of THMs and HAAswhen waters were dosed with typical levels of UV radiation. This manifested itself as 8-23% increases in the two regulated DBP groups at short chlorine contact times. Priorstudies have only considered long reaction times, which might explain why these effectshave not previously been reported. In addition, there were substantial increases in TOXas a result of UV pretreatment. These increases ranged from 85-270% after about 30minutes of contact time. What is apparent from this data is that UV treatment has amuch greater influence on DPB precursors than previously recognized. It also appears toproduce a different distribution of DBPs, favoring the non-THM, non-HAA byproducts. Includes 17 references, tables, figures.

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Edition: Vol. - No. Published: 11/02/2003 Number of Pages: 14 File Size: 1 file , 710 KB