In order to
comply with the impending Stage 2 Disinfectants and Disinfection Byproducts Rule (DBPR) and reduce disinfection byproduct (DBP) levels at the far
ends of their distribution systems, some utilities have already converted and
many are considering converting from free chlorine to chloramines for
secondary disinfection.
For many utilities, the addition of ammonia to water with a free chlorine
residual to form chloramines is an automated process. Traditionally, utilities
have programmed their control systems so that the amount of ammonia being
added depends on flow, free chlorine residual, and a set chlorine to ammonia
ratio. However, this approach to dose control can lead to
fluctuations in finished water free ammonia levels if the free chlorine residual
in the finished water fluctuates. The risk of over or underfeeding that exists with the traditional ammonia feed
control approach can be reduced by an ammonia feed control approach that is
based on achieving a fixed excess free ammonia residual level. This approach
will allow a consistent excess free ammonia residual level to be maintained
during fluctuations of the chlorine residual. The key to the approach is that
the calculation of the required ammonia dose is based on a set free ammonia
level, while the chlorine to ammonia-nitrogen ratio is allowed to vary. This
approach does not require the measurement of free ammonia levels in the
water, thus avoiding the need to measure excess free ammonia levels for
process control.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 210 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 3 |
| Published : | 09/01/2005 |
