Wastewater Calculations - Mathematics and Statistics for the Environment - page 707

117 lb/day chlorine
65 availablechlorine
100

=180 lb/day hypochlorite

■ EXAMPLE 24.67
Problem: A wastewater flow of 840,000 gpd requires a chlorine dose of 20 mg/L. If sodium
hypochlorite (15% available chlorine) is to be used, how many lb/day of sodium hypochlorite are
required? How many gallons per day of sodium hypochlorite is this?

Solution: First calculate the lb/day chlorine required:

Chlorine (mg/L) × Flow (MGD) × 8.34 lb/gal = lb/day chlorine

20 mg/L × 0.84 MGD × 8.34 lb/gal = 140 lb/day chlorine

Then calculate the lb/day sodium hypochlorite:

140 lb/day chlorine
15 availablechlorine
100

= 933 lb/day hypochlorite

Now calculate the gpd sodium hypochlorite:

933 lb/day
8.34 lb/gal

= 112 gpd sodium hypoch lorite

■ EXAMPLE 24.68
Problem: How many pounds of chlorine gas are necessary to treat 5,000,000 gal of wastewater at
a dosage of 2 mg/L?

Solution: First calculate the pounds of chlorine required:

Volume (10 6 gal) × Chlorine concentration (mg/L) × 8.34 lb/gal = lb chlorine

Then substitute:

(5 × 10 6 gal) × 2 mg/L × 8.34 lb/gal = 83 lb chlorine

24.10.4 C hemiCal s olutions
A water solution is a homogeneous liquid consisting of the solvent (the substance that dissolves
another substance) and the solute (the substance that dissolves in the solvent) (Figure 24.7). Water
is the solvent. The solute (whatever it may be) may dissolve up to a certain point. This is called its
solubility— that is, the solubility of the solute in the particular solvent (water) at a particular tem-
perature and pressure. Remember, in chemical solutions, the substance being dissolved is called
the solute , and the liquid present in the greatest amount in a solution (and that does the dissolving)
is called the solvent . We should also be familiar with another term, concentration— the amount of
solute dissolved in a given amount of solvent. Concentration is measured as

Weight of solute
Weight of soluti

Weight of solute
Weight of solute

%Strength = ×= 100 ×100 (24.94)

on + so lvent