Wastewater operator math practice, solved step by step
Free math practice for the Texas Class D wastewater exam: detention time, percent removal, loading, and flow. Work each one on paper, then watch it solved one small step at a time, with a plain-words explanation under every step. Built for people who have been out of school a while.
Wastewater math topics
Detention time
How long water sits in a tank: divide the volume by the flow, keeping the units matched.
Practice itPercent removal
How much a plant took out: (amount in minus amount out) divided by the amount in, times 100.
Practice itFlow rate and conversions
Flow is amount divided by time; move between GPM, GPD, and MGD with 1,440.
Practice itArea and volume of basins
Length times width for area, then times depth for volume, before any loading math.
Practice itEvery practice problem
Work it on paper, then watch it solved one small step at a time.
- Water & wastewaterHow much pressure does 92 feet of water make?Try it, then watch
- Water & wastewaterHow many gallons are in a 20 by 10 by 8 foot tank?Try it, then watch
- Water & wastewaterHow many pounds of chlorine for 2 MGD at 3 mg/L?Try it, then watch
- Water & wastewaterHow do you turn 350 GPM into gallons per day?Try it, then watch
- WastewaterWhat is the detention time of a 30,000 gallon tank?Try it, then watch
- WastewaterWhat percent of the BOD was removed?Try it, then watch
- Water & wastewaterWhat is the area of a 40 by 12 foot clarifier?Try it, then watch
- Water & wastewaterWhat is the flow if 6,000 gallons fill in 30 minutes?Try it, then watch
- Water & wastewaterHow many GPM is 1.44 MGD?Try it, then watch
- Water & wastewaterHow much does 500 gallons of water weigh?Try it, then watch
- Water & wastewaterHow many gallons are in 2,000 cubic feet?Try it, then watch
- Water & wastewaterWhat is the detention time in minutes for 5,000 gallons at 250 GPM?Try it, then watch
- Water & wastewaterHow many feet of head is 50 psi?Try it, then watch
- Water & wastewaterWhat percent of capacity is 400 GPM out of 500?Try it, then watch
- Water & wastewaterWhat is the area of a 20 foot round clarifier?Try it, then watch
- Water & wastewaterWhat is the area of a 30 by 15 foot basin?Try it, then watch
- Water & wastewaterHow many pounds of chlorine for 0.5 MGD at 2 mg/L?Try it, then watch
- WastewaterWhat is the detention time of a 100,000 gallon tank at 25,000 GPH?Try it, then watch
- WastewaterWhat percent of the TSS was removed, 240 to 60?Try it, then watch
- Water & wastewaterHow much pressure is at the bottom of a 40 foot tank?Try it, then watch
- Water & wastewaterHow do you turn 720,000 GPD into MGD?Try it, then watch
- Water & wastewaterWhat is the area of a 25 foot round tank?Try it, then watch
- Water & wastewaterWhat is the area of a 50 by 20 foot basin?Try it, then watch
- Water & wastewaterHow many GPD is 1,000 GPM?Try it, then watch
- Water & wastewaterWhat is the flow if 12,000 gallons fill in 40 minutes?Try it, then watch
- Water & wastewaterWhat is the detention time for 60,000 gallons at 500 GPM?Try it, then watch
- WastewaterWhat percent of the BOD was removed, 180 to 36?Try it, then watch
- Water & wastewaterHow much pressure does 150 feet of water make?Try it, then watch
Keep practicing
All practice problems
The full set of worked problems for both tracks, solved step by step.
The math method, solved simply
The plain-language method behind each formula, worked the simplest way.
Free operator calculators
Plug in your own numbers for volume, dose, flow, and pump run time.
Free practice tests
Ready to test yourself once the method feels solid.
Common questions
- What math is on the Texas Class D wastewater exam?
- One- and two-step problems: area and volume, flow rate, detention time, dosage, and basic loading. It is closed-book, but you are given a formula and conversion sheet.
- Are these real exam questions?
- No. Every problem is original teaching material written to practice the same math the exam uses. Nothing here predicts your official score.
- Is the wastewater math practice free?
- Yes. Every worked problem is free, with the full step-by-step walkthrough and a plain-words explanation.
- How is detention time calculated?
- Detention time is the volume divided by the flow. Keep the units matched, so gallons divided by gallons-per-hour gives hours.
Preparing for the whole exam?
The full Texas Class D prep, when you are ready
These worked problems are free. When you want the full picture, the reviewed question bank covers every Class D subject, with a guided study path, drills, and a timed practice exam.
- Reviewed questions for every Class D subject
- A guided study path that tells you what to do next
- A timed practice exam that mirrors the real format
- Operator math worked step by step, with calculators
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