Exam Practice Questions And Correct

Texas Wastewater Operator Class D Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a wastewater treatment plant?
• Increase water hardness
• Reduce pollutants to protect public health
• Remove all microorganisms
• Increase water temperature

Answer: B

Rationale: The main goal of a wastewater treatment plant is to

remove contaminants from wastewater to protect public health and the environment. 1 / 4

• Which of the following is considered a domestic wastewater

pollutant?

• Oil
• Heavy metals
• Human waste
• Pesticides

Answer: C

Rationale: Domestic wastewater primarily contains human waste,

soaps, and food residues.

• Which process in wastewater treatment removes large solids?
• Filtration
• Screening
• Chlorination
• Sedimentation

Answer: B

Rationale: Screening uses physical barriers to remove large objects like

rags, sticks, and plastics from wastewater.

• What is the primary function of primary sedimentation?
• Remove dissolved chemicals
• Settle suspended solids
• Kill bacteria
• Reduce odors

Answer: B 2 / 4

Rationale: Primary sedimentation allows heavier solids to settle out of

the wastewater.

• What is BOD?
• Biochemical Oxygen Demand
• Biochemical Oxygen Demand
• Basic Oxidation Density
• Biological Organic Distribution

Answer: B

Rationale: BOD measures the amount of oxygen microorganisms

require to decompose organic matter in wastewater.

6. A high BOD indicates:

• Low organic content
• High organic content
• Low solids
• High chlorine

Answer: B

Rationale: High BOD means there is a large amount of organic

material for bacteria to consume.

• What type of bacteria is primarily responsible for decomposing

organic matter in wastewater?

• Cyanobacteria
• Heterotrophic bacteria
• Autotrophic bacteria 3 / 4

• Algae

Answer: B

Rationale: Heterotrophic bacteria consume organic matter and

convert it into simpler compounds.

• Which treatment process is aerobic?
• Anaerobic digester
• Activated sludge process
• Septic tank
• Trickling filter under anaerobic conditions

Answer: B

Rationale: Activated sludge relies on oxygen and aerobic bacteria to

break down organic matter.

• Which unit operation is primarily used to remove nitrogen in

wastewater?

• Primary sedimentation
• Biological nitrification/denitrification
• Chlorination
• Screening

Answer: B

Rationale: Nitrification and denitrification are biological processes that

convert ammonia into nitrogen gas.

• What is the main function of a trickling filter?
• Chlorinate wastewater
• / 4