Disinfection - Wastewater Operators - page 354

9.2.8.4 Available Chlorine

When hypochlorite forms of chlorine are used, the available chlo-
rine is listed on the label. In these cases, the amount of chemical added
must be converted to the actual amount of chlorine using the following
calculation:

Available Chlorine = Amount of Hypochlorite × % Available Chlorine (9.4)

 Example 9.4

Problem: The calcium hypochlorite used for chlorination contains 62.5%
available chlorine. How many pounds of chlorine are added to the plant
effluent if the current feed rate is 30 lb of calcium hypochlorite per day?

Solution:

Quantity of Chlorine = 30 lb × 0.625 = 18.75 lb

9.2.8.5 Required Quantity of Dry Hypochlorite

This calculation is used to determine the amount of hypochlorite
required to achieve the desired dose of chlorine:

⎡ Required Chlorine Dos e (mg/L) ⎤

⎢ ⎥

(9.5)

× Flow (MGD) × 8.34 lb/MG/mg/L

⎣ ⎦

Hypochlorite (lb/day) =

% Available Chlorine

 Example 9.5

Problem: The laboratory reports that the chlorine dose required to main-
tain the desired residual level is 8.5 mg/L. Today's flow rate is 3.25 MGD.
The hypochlorite powder used for disinfection is 70% available chlorine.
How many pounds of hypochlorite must be used?

Solution:

8.5mg/L3.25MGD × × 8.34 lb/MG/ mg/L

Hypochlorite = = 329lb/day

0.70

9.2.8.6 Required Quantity of Liquid Hypochlorite

⎡ Required Chlorine Dose ( mg/L) ⎤

⎢ ⎥

× Flow (MGD) × 8.34 lb/MG/mg/L

⎣ ⎦

Hypochlorite (gpd) =

(9.6)

⎡
⎣ ⎢

⎤
⎦ ⎥

% Av ailable Chlorine × 8.34 lb/gal

× Hypochlorite Solution Specific Gravity