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2009 Nalco Company
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Technical Help
(630) 305-CHEM
3D TRASAR
5500 - Installation & Operation Manual
42. My Nalco Bio-Index has been reading -80 for the past week. Is there a problem?
There are several causes for a persistently low Nalco Bio-Index:
• Is your Makeup water highly halogenated? Are there other sources of oxidant feed into the
tower? Persistent very negative Nalco Bio-Index readings indicates that the bio-reporter is being
degraded by a separate oxidant feed. Plot the ORP(mV) data from the standard log and see how
it varies over time. Other sources of oxidant can be detected by the ORP being maintained or
going up with makeup water ingress.
• Your HTI may be too low for 3D TRASAR Bio-Control.
• Is there any other alarm condition on your controller? Other conditions may be causing the low
Nalco Bio-Index.
43. My Nalco Bio-Index is negative. Why is my oxidizing biocide pump on?
Nalco Bio-Index (NBI) value is NOT used to make decisions on oxidant feed and is for display
purposes only.
NBI represents the average value of the Rf/Rz Ratio with respect to the control band over the past
6 hours. Because it is an averaged value, the response time of this function is slow.
44. 3D TRASAR Bio-Control is controlling, but no oxidizing biocide is being fed.
Why?
Did you reboot (cycle power) on the controller after changing control modes?
The standard data log saves a snapshot of the state of the relay every 15minutes. The relay may
have been in between these logs. The calc (once-a-day) log correctly records the Oxidizing biocide
relay duty cycle for the past 24 hours. Check this number to determine if biocide has been applied
or not. The 3D Bio data also logs the Ox relay on times accurately.
If the system has just been dosed with bio-reporter, it will take between 4-24 hours (depending on
microbial activity) for the ratio to reach the control ratio set point. During this period, oxidizing
biocide will not be applied to the system. If, after 24 hours, oxidizing biocide has not been fed into
the system, please call the help-desk.
Do you have highly halogenated makeup water or other sources of oxidant feed into your system?