Introduction - Mathematics and Statistics for the Environment - page 16

TABLE 1.5
Weight, Volume, and Concentration Calculations

To Calculate Formula

Pounds

Concentration (mg/L) × Tank Volume (MG) × 8.34 lb/mg/L/MG

Pounds/day

Concentration (mg/L) × Flow (MGD) × 8.34 lb/mg/L/MG

Quantity (lb/day)
Concentration(mg/L)

Million gallons/day

8.3× lb/mg/L/MG

Quantity (lb)
Tank volume(MG)

Milligrams/liter

× 8.34 lb/mg/L/ MG

Kilograms/liter

Concentraiton (mg/L) × Volume, (MG) × 3.785 lb/mg/L/MG

Kilograms/day

Concentration (mg/L) × Flow (MGD) × 3.785 lb/mg/L/MG

Pounds/dry ton

Concentration (mg/kg) × 0.002 lb/dry ton/mg/kg

Note: Density (also called specific weight ) is mass per unit volume and may be written as lb/ft 3 , lb/
gal, g/mL, or g/m 3 . If we take a fixed-volume container, fill it with a fluid, and weigh it, we
can determine the density of the fluid (after subtracting the weight of the container).

• 1 gallon of water weighs 8.34 pounds; the density is 8.34 lb/gal
• 1 milliliter of water weighs 1 gram; the density is 1 g/mL
• 1 cubic foot of water weighs 62.4 pounds; the density is 62.4 lb/gal
• 8.34 lb/gal = milligrams per liter, which is used to convert dosage in mg/L into lb/day/
MGD (e.g., 1 mg/L × 10 MGD × 8.34 lb/gal = 83.4 lb/day)
• 1 psi = 2.31 feet of water (head)
• 1 foot head = 0.433 psi
• °F = 9/5(°C + 32)
• °C = 5/9(°F - 32)
• Average water usage, 100 gallons/capita/day (gpcd)
• Persons per single family residence, 3.7

1.4.2 W ater /W asteWater C onversion e xamples
Use Tables 1.4 and 1.5 to make the conversions indicated in the following example problems. Other
conversions are presented in appropriate sections of the text.

■ EXAMPLE 1.4
Convert cubic feet to gallons.

Gallons = Cubic feet (ft 3 ) × gal/ft 3

Problem: How many gallons of biosolids can be pumped to a digester that has 3600 ft 3 of volume
ava ilable?

Solution:

Gallons = 3600 ft 3 × 7.48 gal l /f ft3 3 = 26,928 gal