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2009 Nalco Company
6-2
Technical Help
(630) 305-CHEM
3D TRASAR
5500 - Installation & Operation Manual
6.1
Nalco Bio-Index Measurement (NBI)
The Nalco Bio-Index measurement is a calculated variable used to measure the historical system
response to biocide feed. It is NOT used to control the feed of oxidizing biocide. The table below
shows the correlation between cooling system biological stress level and the Nalco Bio-Index
number. Please note that the NBI can be negative during normal operation.
!
NOTE
: 3D TRASAR Bio-Control cannot be run in ‘Monitoring Mode’. For NBI numbers to
be meaningful, 3D TRASAR Bio-Control MUST be in control of the oxidant feed pump (e.g.
no external ‘slug feed’ or external control of oxidant feed). During controller based slug
feed of oxidizing biocide the NBI reverts to –999 since the bio-reporter is not in control of
the Oxidant during that period.
6.2 Oxidizing Biocide Application and Slug Feeds
For most normally operating systems, 3D TRASAR Bio-Control applies the necessary biocide to
maintain microbiological control. In some systems, additional dosing of biocide may be desired for
a variety of reasons, including:
1. System has recirculation problems (with zones which have stagnant or slow-moving water)
2. System is struggling with algae control
3. Good BioManage™ practices stipulate a need to vary the stresses experienced by the
microbial population.
4. Positive
Legionella
counts require a slug dose of Oxidizing biocide into the system
5. Routine oxidant slugs are a part of the water hygiene response plan
6. System needs to respond to a process leak
Nalco Bio-Index Reading
System Biological Stress Level
<-20
Often seen within 48 hours of startup. If
persistent, call help desk.
-20 to +10
Low
10 to 30
Mild
30 to 80
High
> 80
Very High
Nalco Bio-Index Reading
System Biological Stress Level
-999 or ---
Bio-reporter is not in control of Oxidizing Biocide
-250 to 0
Bio-reporter is measuring microbiological activity.
Increasing Nalco Bio-Index indicates increased
microbiological activity
0
System is about to slug Oxi dizing Biocide
Table 6.1a Nalco Bio-Index Reading for 3D TRASAR Bio-Control.
Table 6.1b Nalco Bio-Index Reading for 3D TRASAR Bio-Shock mode.
