Dechlorination of Highly Chlorinated Water - Disinfection of Pipelines and Storage Facilities Field Guide - page 104

(c7-4)

Dechlori-
nation
chemical
feed rate
(mL/min)

Chlorinated
water flow
rate (L/sec)
(withdrawal
or fill)

Chlorine
residual
(mg/L)

Dechlori-
nation
chemical
dosage
(Table 7-2)

Strength of
dechlori-
nation
chemical
solution (%)

= 6 × × × ÷

These calculators are used in the situation where dechlorina-
tion is applied to a continuous flow. The three calculators are
used to determine the dechlorination feed rate in either gallons
per hour, milliliters per minute with the continuous flow in gallons
per minute, or liters per second. The calculators have four factors.
Insert the values for each factor and calculate the dechlorination
feed rate.
￿

The first factor is the flow rate of the chlorinated water
(withdrawal or fill rate) to be dechlorinated.

￿ The second factor is the chlorine residual in mg/L.

￿ The next factor is the dechlorination chemical dosage

from Table 7-2.

￿ The last factor is the strength of the dechlorination

chemical solution in %.

Example 1. The slug method is used for chlorination of
1,000 ft of 10-in. diameter pipeline. A 20% slug volume was
selected because the job needed to be completed in about 16 hr.
Dechlorinate as the slug exits the pipeline using a 1% sodium
sulfite solution. Describe the dechlorination process of the slug
as it is slowly withdrawn from the pipeline.
￿ Use calculator c3-6 and Table 3-6 to determine the

volume of the slug.
1,000 ft

4.08 gal/ft 0.2 = 816 gal and the chlorine

× ×

residual is 100 mg/L

￿ Use calculator c3-7 to determine the withdrawal rate.

816 gal ÷ 180 min = 4.5 gal/min