Environmental Engineering Reference
In-Depth Information
4. Fill the pipeline containing the calcium hypochlorite
granules or tablets slowly (not more than 1 ft/sec).
Remove air pockets. Flush this chlorinated water from
the pipeline. Dechlorinate this water is necessary.
5. Supply a constant flow rate, to fill the pipeline and when
forming and moving the slug, from a temporary, backflow-
protected source or other approved supply source. Deter-
mine the flow using a pitot gauge in the discharge (other
type of meter), measuring the time to fill a precalibrated
container, or use the trajectory discharge method (shown
in Figure 3-3).
6. Inject the concentrated chlorine solution no more than
10 ft (3 m) from the beginning of the new main. The dosage
should be at least 100 mg/L free chlorine. Tables 3-10,
3-11, and 3-12 list the liquid chlorine, sodium hypochlo-
rite, and calcium hypochlorite application rates to
achieve this dosage. Prepare a 1 percent chlorine solution
by mixing 1 lb (454 g) of calcium hypochlorite or 3 L of 10
percent strength sodium hypochlorite solution in 8 gal
(30.3 L) of water.
7. Measure the chlorine residual (near the injection point)
regularly to verify the concentration (high-range chlorine
test kit or applicable method in current edition of
Standard Method for the Examination of Water and
Wastewater or AWWA Manual M12).
8. Apply chlorine continuously to develop a solid column, or
slug, of chlorinated water that will expose all interior sur-
faces to a concentration of approximately 100 mg/L for at
least 3 hr. Measure the chlorine residual at the end of the
slug to verify the concentration.
9. Measure the free chlorine residual as the slug moves
through the new pipeline (Table 3-12). If the residual
drops below 50 mg/L at any point, stop the procedure and
add chlorine to the slug area to restore the free chlorine
concentration to at least 100 mg/L. Choose sample loca-
tions that will verify the minimum contact time of 3 hr.
10. Operate valves and hydrants as the slug passes them to
disinfect appurtenances and pipe branches.
Search WWH ::




Custom Search