Answer: High BOD effluent would consume oxygen in receiving water bodies, causing death of aquatic life.
- A To prevent offensive odors mainly, with little concern for aquatic oxygen levels overall
- B High BOD effluent would consume oxygen in receiving water bodies, causing death of aquatic life
- C To make the discharged water colorless mainly for aesthetic purposes and appearance
- D To eliminate most pathogenic microorganisms present in the treated wastewater stream
Correct answer: B. High BOD effluent would consume oxygen in receiving water bodies, causing death of aquatic life
Explanation: If effluent with high BOD is discharged, the microorganisms in the receiving water body would consume large amounts of dissolved oxygen to decompose organic matter, causing oxygen depletion and killing fish and other aquatic organisms.
Sewage passes through physical removal (primary), then aerobic biological treatment where microbes form flocs that consume organic matter (secondary); the settled activated sludge is then digested anaerobically to produce biogas - a deliberate switch from aerobic to anaerobic conditions between stages.
Concept context
Microorganisms in food, medicine, sewage treatment, biocontrol, and biofertilizers