Water Treatment Processes - Mathematics and Statistics for the Environment - page 611

increasing operating convenience, leveling pumping requirements (to keep pumps from running 24
hours a day), decreasing power costs, providing water during power source or pump failure, provid-
ing large quantities of water to meet fire demands, providing surge relief (to reduce the surge associ-
ated with stopping and starting pumps), increasing detention time (to provide chlorine contact time
and satisfy the desired contact time value requirements), and blending water sources.
23.3.1 W ater s torage v olume C alCulations
The storage capacity, in gallons, of a reservoir, pond, or small lake can be estimated using
Equation 23.16:
Capacity (gal) = Average length (ft) × Average width (ft) × Average depth (ft) × 7.48 (gal) l /f (ft) 3 (23.16)
■ EXAMPLE 23.17
Problem: A pond has an average length of 250 ft, an average width of 110 ft, and an estimated aver-
age depth of 15 ft. What is the estimated volume of the pond in gallons?
Solution:
Volume = Average length (ft) × Average width (ft) × Average depth (ft) × 7.48 ga l /f (ft) 3
= 250 ft × 110 ft × 15 ft × 7.48 gal l /f ft 3 = 3,085,500 gal
■ EXAMPLE 23.18
Problem: A small lake has an average length of 300 ft and an average width of 95 ft. If the maxi-
mum depth of the lake is 22 ft, what is the estimated volume (in gallons) of the lake?
Note: For small ponds and lakes, the average depth is generally about 0.4 times the greatest depth;
therefore, to estimate the average depth, measure the greatest depth and multiply that number
by 0.4.
Solution: First, the average depth of the lake must be estimated:
= 22 ft × 0.4 ft = 8.8 ft
Then, the lake volume can be determined:
Volume = Average length (ft) × Average width (ft) × Average depth (ft) × 7.48 ga l /f (ft) 3
= 300 ft × 95 ft × 8.8 ft × 7.48 gal l /f ft 3 = 1,875,984 gal
23.3.2 C opper s ulFate d osing
Algal control by applying copper sulfate is perhaps the most common in situ treatment of lakes,
ponds, and reservoirs; the copper ions in the water kill the algae. Copper sulfate application meth-
ods and dosages will vary depending on the specific surface water body being treated. The desired
copper sulfate dosage may be expressed in mg/L copper, lb copper sulfate per ac-ft, or lb copper
sulfate per acre. For a dose expressed as mg/L copper, the following equation is used to calculate lb
copper sulfate required: