Databases on Cryptosporidium occurrence in filtered surface water supplies can be used to
estimate the benefit of providing ultraviolet (UV) disinfection and the consequences of an interruption of the
UV disinfection system operation. Calculations show that a conventional treatment plant could
operate without UV disinfection for 7 days per year (or an average of 14 hours per month) before
exceeding the 1/10,000 annual risk of Cryptosporidium infection. However, the down time
would be limited to only 3.67 hours per month during the spring months, when Cryptosporidium
levels are the highest. The results demonstrate that UV disinfection systems can be brought back
on-line within a practical time frame (i.e., several hours) after a power outage or equipment
malfunction and that brief interruptions of a UV disinfection system would not create an
unacceptable risk assuming continued operation of an upstream conventional treatment process.
A similar approach was used to estimate the limits of operation when a UV system was
performing outside of its validated operating criteria, and for unfiltered water systems. Although
data are limited, and additional data are needed to refine the analysis, the study concludes that
continuous operation of UV systems is not needed to achieve acceptable risk goals and that
extraordinary measures to increase UV disinfection system reliability (e.g., provision of UPS)
provide marginal benefits provided a backup power source is available. Includes 28 references, tables, figure.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 330 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 10 |
| Published : | 06/17/2004 |
