With the finalization of U.S. Environmental Protection Agency's (USEPA's) Ultraviolet Disinfection Guidance Manual, utilities
face the complex process of evaluating the relative benefits and challenges
associated with ultraviolet (UV) disinfection. Among these issues are lamp sleeve
fouling, its probability of occurring at a given location, and the efficacy of various
foulant removal methods. In this study, long term fouling for a medium pressure
reactor utilizing a mechanical-only abrasive sleeve cleaning system was examined.
A 4-lamp, medium-pressure UV disinfection reactor was operated for 15 months
downstream of a conventional water treatment plant treating a blend of California
State Project water (SPW) and Colorado River water (CRW). Prior to UV
disinfection, the water was treated by a conventional treatment plant consisting of
raw-water ozonation, coagulation, flocculation, sedimentation, and biologically-active,
anthracite-sand filtration. During this time the UV sleeve cleaning system
was active and water chemistry conditions were periodically recorded. After
removal from the reactor, spatial distribution of sleeve UV transmittance was
characterized and composition and quantity of lamp sleeve exterior fouling
materials were identified.
Significant exterior, and interior, sleeve fouling was discovered. The interior
foulant was confirmed to consist of relatively high concentrations of calcium,
magnesium, sulfur, and phosphorus in two of the four sleeves. Sleeve UVT
measurements identified a reduction in transmittance from 92% (typical for clean
quartz sleeves) to less than 10% in some locations. After removal of both the
interior and exterior foulants, UVT was still low, indicating a permanent reduction in
sleeve UVT, perhaps by quartz solarization. While lamp sleeve exterior fouling
often depends on water chemistry and operating conditions, sleeve interior fouling
may be influenced by different issues, such as lamp materials, handling of lamps
and sleeves during installation, and orientation (vertical vs. horizontal) of sleeves
during use. A mineral saturation index model was created to investigate the
possible impact on fouling of changes in water oxidation reduction potential. Includes 9 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 270 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 12 |
| Published : | 11/01/2007 |
