Question

Polluted water having low BOD is most economically treated in

• A. Sedimentation tanks
• B. Oxidation ponds
• C. Sludge digester
• D. Clarifier

Hint:

Oxidation ponds are economical biological treatment units for wastewater with relatively low BOD.

Answer 1

The Correct Option is B

BOD means biochemical oxygen demand. Low BOD wastewater contains relatively low biodegradable organic matter. For such wastewater, simple and economical biological treatment methods are suitable. Oxidation ponds are shallow ponds where wastewater is treated naturally. Microorganisms degrade organic matter present in wastewater. Algae produce oxygen by photosynthesis, which supports aerobic decomposition. Oxidation ponds are low-cost and require less mechanical equipment. Sedimentation tanks mainly remove suspended solids. Sludge digesters treat sludge, not low BOD wastewater directly. Clarifiers are used for settling solids. Therefore, polluted water having low BOD is most economically treated in: \[ \text{Oxidation ponds}. \]