521-OM0108.88
Copyright
2009 Nalco Company
6-37
Technical Help
(630) 305-CHEM
3D TRASAR
5500 - Installation & Operation Manual
39. What should I monitor in my tower to ensure good microbiological control?
It is strongly recommended that the tower be monitored routinely to ensure that the tower is under
good control. We recommend that you benchmark performance prior to 3D TRASAR Bio-Control
for later comparison with system performance under 3D TRASAR Bio-Control. The following test
regimen are recommended:
• Monitor planktonic counts with dip slides weekly.
• Send water samples for Bio analysis (DMA-Differential Microbial Analysis) at least quarterly.
• Monitor sessile populations with surface swabs at least quarterly.
40. My dip slides show >10,000 cfu/ml. Does this mean 3D TRASAR Bio-Control does
not work in my system?
No
. 3D TRASAR Bio-Control may be working well in your system. The bio-reporter monitors the
total system microbial activity: planktonic (floating) and sessile (biofilm). The biofilm constitutes the
vast majority of the microbial population in the system (>98%) and is unevenly distributed over the
system surfaces. Dip slides and normal DMA only monitor the floating population, which may not
represent the bulk of the microbial activity.
Planktonic counts measured by dip slides or DMAshould be between 10
3
-10
5
cfu/ml. Swabs of
coupons in systems with 3D TRASAR Bio-Control give population counts of 10
7
cfu/sq cm or less.
Excursions outside this range may happen occasionally, especially after a detergent feed or the
opening of a dead-leg. If the problem persists, please call 630-305-CHEM.
It is important to implement a full microbial treatment plan for the system including use of a
biodetergent (to allow penetration of the bio-reporter and also the oxidizing biocide into the depos-
its) and a non-oxidizing biocide. High planktonic counts may be indicative of continuous inoculation
of the system from dispersing biofilm.
41. I just started 3D TRASAR Bio-Control. Why am I not feeding oxidant?
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 630-305-CHEM.
Since the system has just been dosed with the bio-reporter, the Ratio is low and it is below the
control band. As the microbes convert some of the bio-reporter the Ratio will come up to the set
point. The Nalco Bio-Index is calculated from the averaged value of the Ratio and is not a good
indicator of the Bioactivity in the system at system startup.