and alka-
for dose determination can also be developed from a knowledge of
linity of each stratum and use of the nomograph from Kennedy and Cooke (1982)
(see Figure 7).
For dose determination, a vertical series of water samples is obtained
and alkalinity is determined.
Then, other water samples from the same depths
are titrated with stock solutions of alum to
6.0.
The relation between the
aluminum dose and the alkalinity and
is then used to obtain the maximum
dose for any reservoir alkalinity over the range of alkalinity and
tested.
The maximum dose for each depth interval
calculated from the titration and
water volume for that depth interval, and these are summed to produce the
total dose for the reservoir, or section of the reservoir.
Accuracy in treat-
ing the reservoir is obtained by dividing the treatment areas, or the reser-
voir, into zones marked by buoys.
The volume and alkalinities in each of the
zones are measured, and the amount of alum is then determined.
By dividing
the reservoir into sections, an overdose to shallow areas or an underdose to
deep areas is avoided.
ALUMINUM DOSE,
TO OBTAIN
6.0
250
200
3
150
3
4
100
50
0
7.5
6.5
7.0
8.0
INITIAL
-1
)
Figure 7. Estimated aluminum sulfate dose (mg Al
required to obtain
6 (i.e., "maximum dose") in
treated water of varying initial alkalinity and
(from Kennedy and Cooke 1982)
50
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