Disinfection of Storage Facilities - Disinfection of Pipelines and Storage Facilities Field Guide - page 79

overflow with potable water. The resultant chlorine residual is
suitable for potable use.
Chlorination Steps and Precautions
1. Add chlorine and water to fill about 5% of the storage vol-
ume and result in a chlorine residual of approximately
50 mg/L (Table 5-5). Liquid chlorine and sodium hypochlo-
rite are usually used for this purpose. Calcium hypochlo-
rite granules or tablets can also be used provided that
adequate mixing is available to ensure that the chemical
fully dissolves and is distributed evenly throughout the
facility. Follow procedures described for the full facility
chlorination method.
2. Retain this water within the facility for at least 6 hr.
3. Fill the remainder of the storage facility with potable
water and hold for at least 24 hr.
4. Remove highly chlorinated water from drains and drain
piping.
5. Test the free chlorine residual of the water in the full
facility to ensure that it is at least 2 mg/L. Add more chlo-
rine if the residual is below this value and retest after
another 24 hr retention period. Repeat this process until
satisfactory results are obtained.
Chlorination Amount Calculation
The calculators (c5-1, 5-2, 5-3, 5-4, 5-5, 5-6) and Tables 5-5
and 5-6 should be used to calculate the amount of chlorination
chemical needed to disinfect tanks using the Chlorinate and Fill
Method. These calculations generally involve calculating the vol-
ume of 5 percent of the storage facility (using the tank volume
calculators or Table 5-2 for horizontal cylindrical tanks and Table
5-5 ) and then determining the amount of chlorination chemical
needed ( using the chlorinate and fill method chemical calculator
c5-6 ) to achieve a 50 mg/L concentration in that volume.