Exam math · Treatment math
Chemical dosage
Pounds of chemical needed to hit a target concentration in a given flow. The most famous formula in operator math.
The formula
Pounds per day = flow in million gallons per day x dose in milligrams per liter x 8.34.
The unit trap
The 8.34 constant converts a milligrams-per-liter dose in water to pounds per million gallons. Flow must be in MGD before it enters the formula; gallons per minute smuggled in raw is the standard exam trap.
Worked practice example
Practice plant flow of 2 MGD at a 3 mg/L target: 2 x 3 x 8.34 gives about 50 pounds per day. (Invented numbers.)
On exam day
A formula and conversion table is provided with the standardized exam; the official version is published by the exam provider at gowpi.org. These pages teach the concepts in our own words so the sheet on the desk reads as a reminder, not a puzzle.
The rest of the math
| Volumes | Tank volume |
| Volumes | Pipe and cylinder volume |
| Flow | Flow and velocity |
| Flow | Detention time |
| Treatment math | Percent strength and dilution |
| Treatment math | Removal efficiency |
| Hydraulics | Pressure and head |
| Hydraulics | Pump and horsepower math |
| Foundations | The conversion backbone |
| Foundations | Averages and loading rates |
| Foundations | The formula-first method |
The operator math sheet
One printable page: the exam format, the formula-first drill method, and the unit-conversion discipline that decides the math questions. Free.
No spam. One useful sheet and occasional notes.