South Carolina Biological Wastewater Operator Class C Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf
- Which of the following is the primary purpose of a clarifier in
- Increase dissolved oxygen
- Remove suspended solids
- Reduce pH
- Kill bacteria
wastewater treatment?
Rationale: Clarifiers are designed to settle out suspended solids from
wastewater, allowing for cleaner effluent and reducing the load on subsequent treatment processes.
- What is the most common type of microorganism responsible for BOD
removal in an activated sludge system? 1 / 4
- Protozoa
- Algae
- Bacteria
- Fungi
Rationale: Bacteria are the primary organisms that metabolize
organic matter in activated sludge, reducing biological oxygen demand (BOD).
- Which process is most effective for nutrient removal in biological
- Sedimentation
- Filtration
- Biological nitrogen and phosphorus removal
- Chlorination
wastewater treatment?
Rationale: Biological nutrient removal uses specific bacteria to
convert nitrogen and phosphorus into forms that can be removed from wastewater.
- Which of the following is a symptom of filamentous bacteria
- High pH
- Sludge bulking
- Low BOD
- Increased effluent chlorine demand 2 / 4
overgrowth in activated sludge?
Rationale: Filamentous bacteria can cause sludge to become fluffy
and resist settling, leading to sludge bulking.
- What is the function of aeration in an activated sludge system?
- Remove chlorine
- Provide oxygen for aerobic bacteria
- Reduce sludge volume
- Remove heavy metals
Rationale: Aeration supplies dissolved oxygen needed by aerobic
microorganisms to degrade organic matter.
- Which form of nitrogen is toxic to aquatic life at high concentrations?
- Nitrate
- Ammonia
- Nitrite
- Organic nitrogen
Rationale: Free ammonia (NH3) is toxic to fish and other aquatic
organisms, especially at higher pH and temperature.
7. In an anaerobic digester, the primary gas produced is:
- Oxygen
- Nitrogen
- Methane
- Carbon dioxide
Rationale: Anaerobic digestion breaks down organic matter in the 3 / 4
absence of oxygen, producing methane as a major biogas component.
- What does MCRT (Mean Cell Residence Time) control in activated
- Influent flow rate
- Effluent pH
- Sludge age
- Chlorine dosage
sludge?
Rationale: MCRT represents the average time solids remain in the
system, influencing sludge characteristics and process stability.
- Which is the primary advantage of a trickling filter over activated
- Lower land requirements
- Lower energy requirements
- Faster BOD removal
- Better nutrient removal
sludge?
Rationale: Trickling filters require less mechanical energy because
they rely on passive biofilm processes.
- A sudden drop in dissolved oxygen in an aeration tank may
indicate:
- Over-aeration
- Low BOD load
- Mechanical failure or high organic load
- / 4