Exam with Actual Answers 2025
1. What is the main purpose of a bar screen at a wastewater treatment plant?
A. Remove nutrients
B. Remove large debris
C. Remove grit
D. Remove bacteria
Bar screens are the first line of defense to remove large debris
such as rags and plastics to protect downstream equipment.
2. What does BOD stand for in wastewater treatment?
A. Biological Oxidation Demand
B. Biochemical Oxygen Demand
C. Biological Organic Debris
D. Bacterial Oxygen Depletion
BOD measures the amount of oxygen microorganisms need to
decompose organic matter.
3. What type of bacteria thrives in oxygen-rich environments?
A. Anaerobic
B. Aerobic
C. Facultative
, D. Nitrifying
Aerobic bacteria require oxygen to survive and are essential for
aerobic treatment processes.
4. What is the acceptable range of pH for most biological wastewater
treatment processes?
A. 2.0–4.0
B. 6.5–8.5
C. 9.0–11.0
D. 4.0–6.0
Biological treatment processes operate best in a near-neutral pH
range of 6.5 to 8.5.
5. What is the main purpose of an aeration tank?
A. Remove grit
B. Promote microbial digestion
C. Disinfect the water
D. Settle solids
Aeration tanks add oxygen to support aerobic bacteria that break
down organic matter.
6. Which organism indicates a healthy activated sludge system?
A. Amoebas
B. Free-swimming ciliates
C. Nematodes
D. Filamentous bacteria