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Model TC80
ADENDUM:
DC80
D
E
-C
HLORINATION
A
NALYZER
The following two paragraphs were extracted from “
EPA
Wastewater Technology Fact Sheet
Dechlorination,”
EPA 832-F-00-022
At present, few options exist for reliable long-term measurement of sulfite salts or close-
to-zero levels of residual chlorine in the finished effluent (ASCE and WEF, 1991). In
recent practice, the only viable method for continuous residual chlorine measurement has
been the amperometric technique, but this suffers from loss of accurate calibration at low
concentrations (Finger et al., 1985)…. For these reasons, control of dechlorination—
particularly dechlorination to zero residual—has been problematic. Treatment plant
operators have had to work around this limitation using various control strategies.
One commonly used strategy is the use of a “zero shifted” or “biased” analyzer (WEF,
1996; Nagel, 1994). In this scheme, a residual chlorine analyzer is used and a known
concentration, X, of chlorine is added to the effluent sample to be analyzed. In this
technique, the “zero” point is shifted by the value of X, and residual chlorine or sulfur
dioxide can be inferred from the result of sample analysis.
The ECD Model DC80 De-Chlorination Analyzer uses the “zero shifted” strategy. The TC80 Total chlorine
Analyzer is fitted with a chlorine dosing pump that feeds into the outfall of the Constant Head Flow Controller
and an “Offset” feature to accomplish the “zero point shift”.