Environmental Engineering Reference
In-Depth Information
2. Measure the chlorine residual of the water following the
required retention period. The free chlorine residual
must be at least 10 mg/L. If the chlorine residual is below
10 mg/L, add more chlorine and retain for another period
as described in step 1. Continue this procedure until a free
chlorine residual of at least 10 mg/L is obtained following
the required retention period.
3. Reduce the chlorine residual of the water within the stor-
age facility by draining (dechlorinate if necessary) and
refilling with potable water. Another method of achieving
this result is to hold the water until the chlorine residual
is reduced and blend the remaining water with potable
water.
Chlorination Amount Calculation
The following calculators (c5-1, 5-2, 5-3, 5-4, 5-5) and tables
(5-2, 5-3) should be used to calculate the amount of chlorination
chemical needed to disinfect tanks using the full storage facility
chlorination method. These calculations generally involve calcu-
lating the volume of the storage facility (using the
tank volume
calculators or Table 5-2 for horizontal cylindrical tanks
) and
determining the amount of chlorination chemical needed
(using
the chlorination chemical calculator
) to achieve a 10 mg/L con-
centration in that volume.
The volume of most tanks is calculated using the volume cal-
culators below for rectangular, square, vertical cylindrical, and
horizontal cylindrical tanks. Other shapes will require informa-
tion from the manufacturer or design engineer. Table 5-2 shows
the volume of horizontal cylindrical tanks with some common
dimensions.
The amount of chlorination chemical needed for a unit volume
(either 100,000 gallons or 100 cubic meters) to produce 10 mg/L
dosage is listed in Table 5-3. The values in this table are then
used in the chlorination chemical calculator (c5-5). All three of
the most common chlorination chemicals are included in the
table with both US and SI units of measure.
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