Ultraviolet (UV) treatment has been shown to produce a nearly undetectable level of
disinfection byproducts (DBPs) at the doses commonly used. Most UV treatment
scenarios include either chlorination or chloramination for the purpose of maintaining a
disinfectant residual during distribution. For this reason, there has also been an interest in
impacts 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 to
show a substantial effect at typical UV doses.
The purpose of this research was to expand upon the prior work to include studies
of total organic halide (TOX) and to consider THM and HAA formation under short
incubation times. Raw waters from several chemically and geographically distinct
sources were collected and treated with UV light (low pressure) and chlorine in the
UMass laboratory. Care was taken to use realistic chlorine doses (2-6 mg/L) and
controlled pH, along with medium to high UV doses (400-1500 mJ/cm<sup>2</sup>).
Results showed substantial increases in rate of formation of THMs and HAAs
when 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. Prior
studies have only considered long reaction times, which might explain why these effects
have not previously been reported. In addition, there were substantial increases in TOX
as a result of UV pretreatment. These increases ranged from 85-270% after about 30
minutes of contact time. What is apparent from this data is that UV treatment has a
much greater influence on DPB precursors than previously recognized. It also appears to
produce a different distribution of DBPs, favoring the non-THM, non-HAA byproducts.
Includes 17 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 710 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 14 |
| Published : | 11/02/2003 |
