Dissolved Oxygen (DO)
1. Head to Pressure
A wastewater column 1 foot high exerts a pressure of 0.433 pounds per square inch. The total pressure can be calculated by multiplying the height (depth) of the water by 0.433 psi/foot. The height/depth of the water is also called "head".
Example: The water in the settling tank is 15 feet deep. What is the pressure in pounds per square inch at the bottom of the tank?
2. Pressure to Head
Pressure can also be converted into its equivalent column of water or head. A pressure of 1 psi is the same as a column of water 2.31 feet high.
Work is defined as moving an object (weight) a vertical distance. It is expressed as foot-pounds
Example: How much work is performed if 200 gallons of wastewater are lifted (pumped) a vertical distance of 50 feet?
Power is the amount of work done per unit time. It is expressed in foot pounds per minute.
Horsepower is a common expression for power in wastewater treatment. One horsepower is equal to 33,000 foot pounds of work per minute.
7. Water Horsepower
The amount of power required to move a given volume of water a specified total head.
8. Brake Horsepower
The amount of horsepower to be supplied to the pump to provide the required water horsepower. The efficiency of the pump must be taken into account.
9. Motor Horsepower
The rated horsepower of the motor necessary to produce the desired brake and water horsepower.
Example: The motor is 94% efficient. What is the required motor horsepower when the required brake horsepower is 7.0 Bhp?
10. Electrical Power
Example: A 50 horsepower motor operates at full load 12 hours per daily (seven days per week). How many kilowatt hours of energy does it consume per day?