Chlorine demand of Savannah River water Page: 6 of 30
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Samples were processed the same way on each of the seven
sampling dates. Eight one-liter subsamples from the 15-liter
composite cooling water sample were placed in each of eight,
2-liter Erlenmeyer flasks. The flasks were placed in a
walk-in cooler and cooled to room temperature (75°F - 80“F).
While the samples were cooling, chlorine (laboratory grade
NaOCl containing ca. 5% Cl.) was added to flasks containing
1 liter of double distilled chlorine-demand-free water to
determine the correct quantities of stock sodium
hypochlorite (NaOCl) solution needed to supply preselected
chlorine dosages of 1, 3, and 5 mg/L. Generally, quantities
of 20 Ml* 60 jul, and 100 /il of a stock solution of NaOCl,
resulted in the desired chlorine residuals of 1 mg/1, 3
mg/1, and 5 mg/1. When the expected chlorine residuals did
not occur in the chlorine-demand-free water following
appropriate additions of stock NaOCl solution, the stock
solution was replaced.
All residual chlorine measurements conducted as part of the
study were made by the DPD method using Hach DR-100 test
kits. The decision to use this technique was based on
previous chlorine studies at the site (Wilde, 1986), in
which a series of total residual chlorine (TRC) measurements
made simultaneously by three methods revealed that the DPD
method (Hach DR-100 kit) and the amperometric titration
method produced statistically similar results while an
ion-selective electrode method provided significantly lower
When the effluent cooling water samples that had been placed
in the walk-in cooler had cooled to room temperature, the
flasks were removed, covered with aluminum foil, labeled, and
placed on magnetic stirrers. Stir bars were added. TRC and
free residual chlorine (FRC) were measured in two of the
flasks to determine "background" readings. In addition to
residual chlorine measurements, subsamples from these two
flasks were measured for ammonia nitrogen (Nessler method
using a Hach DR 100 colorimeter)) and pH (using a pH meter).
A chlorine dose of 1 mg/1 Cl. (determined by the chlorine
additions to chlorine-demand-free distilled water described
above) was added to each of a different pair of flasks
containing the cooling water. Subsamples were withdrawn
immediately and simultaneously from both flasks and FRC and
TRC were measured using two Hach DR-100 kits. Additional
subsamples were withdrawn from the two flasks at intervals
of 10, 30, 60, 120, 240, and 1440 minutes (24 hr) and
measured for FRC and TRC. The flasks were kept covered and
stirred except for the brief periods when subsamples were
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Wilde, E.W. Chlorine demand of Savannah River water, report, January 1, 1989; Aiken, South Carolina. (https://digital.library.unt.edu/ark:/67531/metadc1094127/m1/6/: accessed March 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.