Waste and Sewage Disposal MCQs

Explanation: Oxidation ponds (also called stabilization ponds or lagoons) are large, shallow basins used for sewage treatment. Their functioning depends on the interaction between algae and bacteria . Daytime: Algae perform photosynthesis → release large amounts of oxygen into the pond. This oxygen supports aerobic bacteria , which break down organic matter into simpler, non-toxic compounds. Hence, the pond environment is predominantly aerobic . Nighttime: Photosynthesis stops in the absence of sunlight. Microorganisms continue to consume oxygen through respiration . Oxygen levels fall rapidly, and anaerobic conditions may develop, particularly at the bottom layers. This daily oscillation between aerobic (day) and anaerobic (night) conditions is a characteristic feature of oxidation ponds and helps in effective sewage stabilization. (Options A, B & D ruled out)