can of water, one-half of the contents of one calcium hypochlorite ampule should be

used initially as explained in a (3) above; then, additional small amounts should be

added if necessary (a (7) and (8) above). For a 55-gallon drum of water, four or five

ampules should be used initially. For a 400-gallon trailer of water, 30 ampules should

be used initially. Water, in larger containers, is not easily chlorinated by use of ampules.

The use of bulk calcium hypochlorite is described in subparagraph c, below.

c. **Batch Chlorination**. The term "batch chlorination" applies to the practice of

using bulk calcium hypochlorite quantities of water for which the calcium hypochlorite

ampules are not appropriate.

(1) Chlorine demand. In order to determine the required dosage, we

determine chlorine since chlorine residual equals the dosage minus the demand.

Determination of the chlorine demand requires a more accurate method of measuring

the chlorine residual than afforded by the comparator tubes in the chlorination kit. This

procedure is discussed in detail in paragraphs 2-10 and 5-10b. Briefly, it is determined

by adding a known quantity of chlorine (in ppm) to a known amount of raw water and

measuring the chlorine residual after the required contact time.

(2) Available chlorine. Calcium hypochlorite consists of 70 percent active

chlorine. Therefore, when the amount of chlorine required to provide a given residual

has been determined, that figure must be divided by 0.70 to determine the amount of

calcium hypochlorite compound required.

(3) Calculation. To determine the amount of calcium hypochlorite

necessary to provide a chlorine residual of 5 ppm-in a 3,000-gallon container of water

having a chlorine demand of 2 ppm, the following procedure should be followed:

(a) Convert the volume of water to weight:

3,000 gal water x 8.34 lbs/gal = 25,020 lbs

(b) Determine the dosage required:

Dosage = demand (2ppm) + residual (5ppm) = 7 ppm, or

7 lbs chlorine_

1,000,000 lbs water

(c)

Set up the following proportion:

7 lbs chlorine x lbs chlorine

=

X lbs chorine

1,000,000 lbs water

25,020 lbs water

(1,000,000) (x)

=

(7) (25,020)

1,000,000x

=

175,140

175,140

X=

= 0.175 lbs. chlorine (2.8 ounces)

1,000,000

MD0160

2-21

Integrated Publishing, Inc. |