Disinfection of Pipelines - Disinfection of Pipelines and Storage Facilities Field Guide - page 56

Example 1. Using the slug method, chlorinate a 1,000-ft
length of 6-in. diameter pipeline. There are four fire hydrants
and two valves located on the new section of pipeline. The chlo-
rination must be completed in less than 15 hr. A 1 percent
sodium hypochlorite solution is used for this procedure. How
much is needed and describe the process.
Use the checklist to ensure all of the information is col-
lected.

❑ The pipeline diameter and length.

6-in. diameter and 1,000-ft length

❑ Valves, hydrants, tees, and other appurtenances.

Four hydrants and two valves. Chlorinate each with
one calcium hypochlorite tablet.

❑ Volume of chlorination water to disinfect pipeline.

Select a 25% slug from Table 3-12 because less than
15 hr is available. A 25% slug will take 12.5 hr. The
volume of the slug is calculated from c3-6.
1,000 1.47 0.25 = 367.5 gallons

× ×

❑ Amount of chlorine needed to complete the disinfection

procedure.
1% sodium hypochlorite feed rate to match
withdrawal rate of 2 gpm is 1.2 gph (from Table 3-11).
The withdrawal rate and the fill rate are the same. It
takes 3 hr to create the 10% slug, so 1.2 gph 3 hr =

3.6 gal of 1% sodium hypochlorite is needed for the job.

×

☞ Calculate the withdrawal rate using c3-7.

367.5 ÷ 180 = 2.0 gpm for 3-hr contact time along
the pipeline.

Example 2. Use the slug method to chlorinate 2,000 m of
600-mm diameter pipe. Use 5 percent hypochlorite solution
(prepared from calcium hypochlorite) for the procedure. Up to
16 hr are available for the job. How much solution is needed?
Describe the procedure.
Use the checklist to ensure all of the information is collected.