Recently the use of low levels of medium- and low-pressure ultraviolet (UV) light for
successful inactivation of Cryptosporidium parvum oocysts has generated tremendous
excitement in the water industry. While these findings have been corroborated by
numerous independent studies at the bench-scale level, there is little experience in the U.S.
with full scale disinfection of finished water, using UV light. Concerns exist with respect
to the reliability of UV technology and, in addition to biodosimetry experiments to
validate reactor performance for organism inactivation, additional issues include
determination of the performance efficiency of the reactors, effects of suspended metals
or other water characteristics on lamp sleeve fouling, effectiveness and reliability of lamp
cleaning mechanisms, UV measurement sensors' stability, costs associated with
retrofitting UV systems into existing water treatment plants, operation and maintenance
costs associated with employment of UV disinfection, impact of lamp aging on delivery
of target UV doses and impact of UV on disinfection byproduct (DBPs) formation or
degeneration.
Although it is anticipated that experience with UV disinfection will provide information
on some of these issues, certain parameters need to be investigated before water utilities
can commit to using UV disinfection as one of the multiple barriers for protection of
public health from waterborne disease causing organisms. To address some of these
operational issues, American Water, the largest investor owned water utility in the U.S.,
has been actively involved in ascertaining the long-term feasibility of applying UV for
treatment of finished water. A 12 inch diameter 4 x 1 KW, closed chamber UV reactor
was installed after granular activated carbon filtration at the Pennsylvania American
Water treatment plant at Hayes Mine and was operated continuously with a finished
water flow rate of 600 gpm. Over a 12 month period, various chemical (THM, HAA,
UV254, DOC, TOC, metals, nitrate, nitrites) and physical measurements (lamp voltage,
current, sensor measurements) were monitored. Also, parameters such as power
consumption and other operational issues associated with reactor function (i.e. frequency
of power outages, failing components, etc.) were recorded. Reactor validation studies were
performed using Bacillus subtilis spores, MS2 bacteriophage and Deinococcus
radiodurans as a biodosimetery surrogates and utilized various lamp configurations as
well as lamp age. Includes 7 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 290 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 10 |
| Published : | 11/02/2003 |
