Exam math · Treatment math
Removal efficiency
How much of a pollutant a process removes, as a percentage of what came in.
The formula
Efficiency = (in minus out) over in, times 100.
The unit trap
Read which stage the question brackets. Whole-plant efficiency uses raw influent and final effluent; single-process efficiency uses that process's own in and out. Grabbing the wrong pair is the miss.
Worked practice example
Practice influent at 200 units and effluent at 20: (200 - 20) / 200 = 0.90, so 90 percent removal. (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 | Chemical dosage |
| Treatment math | Percent strength and dilution |
| 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.