Has anyone sucessfully used an ORP in a dechlorination system for proper chlorine control below .5 mg/l residual? I know that there are many claims as to having proper control capabilities, but for every one that is for the ORP for chlorine control, there is one against it.
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Use of ORP for Clorine control
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DeltaCascade
Chemical
Results could be expected to vary with overall water quality. Dissolved solids, combined chlorine residuals, etc. Background noise. Also, varying with ORP probe maintenance practice, cleaning and calibration. I'd suggest a trial, comparing ORP with results obtained from an alternate (eg: colorimetric) procedure. And let us know your results?
I'm not exaclty directly answering your question, but I'd bet that ORP could at least show trends, particularly in clean (eg: potable) waters, that could be checked against routine Operator data collection using a spot check / lab test. High levels of combined chlorine, such as in waste waters or cooling tower waters, etc, may increase ORP reading even with no free chlorine (just below breakpoint chlorination point, if ammonia compounds are present)? You'd probably at least increase likley hood of catching process upsets with the on-line probe.
I'm not exaclty directly answering your question, but I'd bet that ORP could at least show trends, particularly in clean (eg: potable) waters, that could be checked against routine Operator data collection using a spot check / lab test. High levels of combined chlorine, such as in waste waters or cooling tower waters, etc, may increase ORP reading even with no free chlorine (just below breakpoint chlorination point, if ammonia compounds are present)? You'd probably at least increase likley hood of catching process upsets with the on-line probe.
Fiscalizador
Chemical
We don't find ORP usefull for chlorine control. The ORP is a non-linear function of pH and Chlorine (and, off course, is also affected by other dissolved chemicals).
We find it acceptable for two uses: a) as a cheap device for detecting the presence of low levels of chlorine. b) as a cheap measurement device, just to provide alarms to operators in case of sudden changes.
For automatic control we use Amperometic/Potentiostatic based devices, which are reasonably accurate and have a short response time. The "best" methods are based in colorimetric technics. They have some disadvantages: High cost, High reagents cost and low response time, which is a very important issue in control.
We find it acceptable for two uses: a) as a cheap device for detecting the presence of low levels of chlorine. b) as a cheap measurement device, just to provide alarms to operators in case of sudden changes.
For automatic control we use Amperometic/Potentiostatic based devices, which are reasonably accurate and have a short response time. The "best" methods are based in colorimetric technics. They have some disadvantages: High cost, High reagents cost and low response time, which is a very important issue in control.
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