Introduction - Mathematics and Statistics for the Environment - page 18

■ EXAMPLE 1.9
Convert milligrams per liter to pounds per day.

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

Problem: How many pounds of solids are discharged per day when the plant effluent flow rate is
4.75 MGD and the effluent solids concentration is 26 mg/L?

Solution:

Pounds/day = 26 mg/L × 4.75 MGD × 8.34 lb/mg/L/MG = 1030 lb/day

■ EXAMPLE 1.10
Convert milligrams per liter to kilograms per day.

Kilograms/day = Concentration (mg/L) × Volume (MG) × 3.785 kg/mg/L/MG

Problem: The effluent contains 26 mg/L of BOD 5 . How many kilograms per day of BOD 5 are dis-
charged when the effluent flow rate is 9.5 MGD?

Solution:

Kilograms/day = 26 mg/L × 9.5 MG × 3.785 kg/mg/L/MG = 934 kg/day

■ EXAMPLE 1.11
Convert pounds to milligrams per liter.

Quantity (lb)
Volume (M

Concentration(mg/L) =

G) × 8.34 lb/mg/L/MG

Problem: The aeration tank contains 89,990 pounds of solids. The volume of the aeration tank is
4.45 MG. What is the concentration of solids in the aeration tank in milligrams per liter?

Solution:

89,990 lb

Concentration = = 2425 mg/L

4.45 MG × 8.34 lb/mg/L /MG

■ EXAMPLE 1.12
Convert pounds per day to milligrams per liter.

Quantity (lb/day)

Concentration(mg/L) =

Volum ee(MGD) × 8.34 lb/mg/L/MG

Problem: The disinfection process uses 4820 pounds per day of chlorine to disinfect a flow of 25.2
MGD. What is the concentration of chlorine applied to the effluent?

Solution:

4820 lb/day
25.2 MGD

Concentration = = 22.9 mg/L

× 8.34 lb/m g/L/MG