Nalco Bio-Index Measurement (Nbi); Oxidizing Biocide Application And Slug Feeds - Nalco 3D TRASAR Series Installation And 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.
Nalco Bio-Index Reading
-20 to +10
10 to 30
30 to 80
Table 6.1a Nalco Bio-Index Reading for 3D TRASAR Bio-Control.
Nalco Bio-Index Reading
-999 or ---
-250 to 0
Table 6.1b Nalco Bio-Index Reading for 3D TRASAR Bio-Shock mode.
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
Technical Help
(630) 305-CHEM
<-20
> 80
0
521-OM0108.88
Copyright © 2009 Nalco Company
®
3D TRASAR 5500 - Installation & Operation Manual
System Biological Stress Level
Often seen within 4 8 hours of startup. If
persistent, call help desk.
Low
Mild
High
Very High
System Biological Stress Level
Bio-reporter is not in control of Oxidizing Biocide
Bio-reporter is measuring microbiological activity.
Increasing Nalco Bio-Index indicates increased
microbiological activity
System is about to slug Oxi dizing Biocide
6-2