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14
7. While operating the recirculating water pump(s) and prior to operat-
ing the cooling tower fan, execute one of the two alternative biocidal
treatment programs described in the following:
• Resume treatment with the biocide which had been used prior
to shutdown. Utilize the services of the water treatment supplier.
Maintain the maximum recommended biocide residual (for the
specific biocide) for a sufficient period of time (residual and time
will vary with the biocide) to bring the system under good biological
control or
• Treat the system with sodium hypochlorite to a level of 4 to 5 mg/L
free chlorine residual at a pH of 7.0 to 7.6. The chlorine residual
must be held at 4 to 5 mg/L for six hours, measurable with standard
commercial water test kits.
If the fluid cooler has been in operation and then shut down for a
duration of time and not drained, perform one of the two previous
biocidal treatment programs directly to the fluid cooler storage vessel
(collection basin, drain down tank, etc.) without circulating stagnant
water over the cooling tower fill or operating the cooling tower fan.
After biocidal pretreatment has been successfully completed, cooling
water may be circulated over the tower fill with the fan off.
When biocidal treatment has been maintained at a satisfactory level for
at least six hours, the fan may be turned on and the system returned
to service. Resume the standard water treatment program, including
biocidal treatment.
Operation