Water Operator Exam Prep

Texas, TCEQ, Wastewater Treatment Plant Operator, Class D

Texas Class D wastewater operator exam details

Last reviewed 2026-08-01. Facts link to their official source.

The Texas Class D wastewater exam is a three-hour, closed-book test at a registered testing center. TCEQ publishes a twenty-subject scope, from statutes and permits through activated sludge and math. You may bring a non-programmable calculator; scratch paper is provided. A 70 percent score passes.

The official subject list

TCEQ publishes exactly what a Class D wastewater operator should know, in twenty subject categories that run from statutes and permits through the treatment train to math. Study to this list, not to a course's table of contents. The math stays at one- and two-step problems: area, volume, flow rate, and dosage rate.

  1. Statutes and Rules
  2. Permits
  3. Design Criteria
  4. Safety
  5. Laboratory
  6. Management
  7. General Knowledge
  8. Collection
  9. Pumping
  10. Preliminary Treatment
  11. Primary Treatment
  12. Ponds
  13. Trickling Filters
  14. Activated Sludge
  15. Process Control
  16. Disinfection
  17. Sludge Digestion
  18. Biosolids Disposal
  19. Effluent Disposal
  20. Math Problems

Source: TCEQ Wastewater Operator Exam Knowledge ('What You Need to Know for a Class D Wastewater Treatment Plant Operator Exam' table.). TCEQ publishes the subjects without weights; we do not invent weights.

Format and rules, with sources

Who runs the exam
TCEQ occupational licensing examination. Under 30 TAC §30.20, the executive director prescribes examination content. The exams are delivered through registered CBT centers.
Source: Texas Administrative Code, Title 30 (30 TAC §30.20 and the TCEQ computer-based testing page.)
Time limit
Three-hour time limit.
Source: TCEQ Computer-Based Testing ('All exams have a 3 hour time limit unless otherwise noted'; Class A exams are the noted six-hour exception.)
Closed book
Closed book. Books and notes are prohibited; only Municipal Solid Waste Supervisor exams are open book.
Source: TCEQ Computer-Based Testing ('Prohibited Aids During Licensing Exams' + MSW-only open-book note under 'Authorized Aids'.)
What you may use
Authorized aids: pen or pencil; proctor-provided monitored scratch paper (collected); a non-programmable calculator. No formula sheet appears in the authorized-aids list.
Source: TCEQ Computer-Based Testing ('Authorized Aids During Licensing Exams'.)
The math scope
Class D math: one- or two-step geometry and algebra problems involving area, volume, flow rate, and dosage rate in wastewater contexts.
Source: TCEQ Wastewater Operator Exam Knowledge (Class D table, 'Math Problems' row.)
Passing score
Minimum passing score: 70 percent.
Source: TCEQ Water System Operator Licensing ('Water Operator Licensing Overview': pass the applicable exam with a minimum score of 70 percent.)
Spanish availability
Available in Spanish by computer-based test.
Source: TCEQ Computer-Based Testing ('Spanish exams now available by computer-based test (CBT)' list names Class D Water System Operator and Class D Wastewater Treatment Facility Operator.)
Results
Immediate exam score and printed analysis at the CBT center; the license is issued within one week of passing.
Source: TCEQ Computer-Based Testing ('CBT license examinations offer' bullet list.)

What TCEQ does not publish

  • Formula or equivalents table supplied during the exam: unverified.
  • Domain weights: not located in the reviewed public TCEQ sources.
  • Question count: not located in the reviewed public TCEQ sources.

We state unknowns plainly instead of guessing. When an official value appears, it will be added with its source and review date.

The formula sheet mistake

Candidates coming from other states often expect a formula sheet at the exam because some states provide one. The TCEQ authorized-aids list names a calculator and provided scratch paper, and no formula sheet. Whether any table appears on the exam screen is unverified. The subject list names using a table of equivalents as a skill; that is a skill statement, not a promise of an exam aid. Prepare as if you must know your conversions and formulas cold.

Exam week

  1. Book or confirm your seat at the registered testing center, and confirm what time to arrive.
  2. Re-drill your two weakest subjects, not everything.*
  3. Do one timed practice run at the three-hour format so the pacing feels familiar.*
  4. Put your approval letter and a non-programmable calculator where you cannot forget them.
  5. Stop early the night before. Rest beats one more hour of cramming.*

Items marked with an asterisk are what experienced operators consistently recommend. They are study advice, not official rules; the official rules are cited above.

Exam day

  1. Bring your approval letter and your non-programmable calculator.
  2. Scratch paper is provided by the proctor and collected afterward, used or not.
  3. Books, notes, and phones stay out. The exam is closed book.
  4. You have three hours. Work in passes: answer what you know, mark what you are unsure about, come back.*
  5. Your score appears immediately, with a printed analysis. Keep that printout either way.

Items marked with an asterisk are what experienced operators consistently recommend. They are study advice, not official rules; the official rules are cited above.