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3D TRASAR
5500 - Installation & Operation Manual
22. How does 3D TRASAR Bio-Control compare to ORP control? (con’t)
3D TRASAR Bio-Control feeds oxidant based on the fluorescent bio-reporter response. It is a
demand based method of oxidizing biocide feed. No set residual is maintained, oxidizing biocide
dosage and timing is varied depending on the microbial loading. The bio-reporter must be fed to
the tower for this control method.
ORP is an electrochemical measurement and the readings from a probe can drift significantly in
short periods. It is important to keep the ORP probe clean and well-calibrated. The bio-reporter is
an optical measurement, and maintenance and drift are not problematic.
For ORP control the user chooses the control setpoint. For bio-reporter control, the control band is
preset depending on the oxidizing biocide chosen.
ORP control applies oxidizing biocide so that the system maintains a set ORP. In bio-reporter
control, oxidizing biocide is applied based on microbial demand and therefore biocide usage is
efficient.
Since oxidizing biocide is dosed based on demand, corrosion is often reduced significantly under
Bio-Control. Therefore is typically a reduction in delignification of wood structures, steel stress
corrosion and cracking, AOX formation under this control method.
23. Does 3D TRASAR Bio-Control maintain Free Residual Halogen?
3D TRASAR Bio-Control uses a fluorescent bio-reporter molecule added to the tower water to
continuously monitor the total microbial activity in a system. When the activity reaches a control set
point, oxidizing biocide is applied. If the initial dose was not sufficient, more biocide is applied, until
the system is brought under control.
When sufficient oxidizing biocide has been added to the system and the microbial activity is
brought into control, the excess oxidant interacts with the reacted bio-reporter. The controller stops
oxidizing biocide application.
Because both the microbial activity and the biocide dosing is continuously monitored it is no longer
necessary to maintain a measurable excess oxidizing biocide in the system (residual halogen).
Under 3D TRASAR Bio-Control, the halogen residual may be between 0.8 ppm to 0.02 ppm as
measured by a total halogen DPD test.
