What is the function of an aeration basin in wastewater treatment?

• A. To settle solids by gravity
• B. To heat the wastewater to kill pathogens
• C. To remove nutrients through chemical precipitation
• D. To provide oxygen to microorganisms to convert organic matter into biomass and CO2, aiding biological treatment

Answer: (D)

Providing oxygen in an aeration basin fuels aerobic microorganisms so they can biologically degrade organic matter. As air is bubbled through the mixed wastewater, these microbes respire, using the oxygen to break down the dissolved and particulate organics. The result is conversion of much of that organic material into new microbial cells (biomass) and carbon dioxide, reducing the wastewater’s organic load and helping drive the treatment process forward. The aeration basin also keeps the solids in suspension and maintains mixing so microbes and pollutants stay in contact long enough for efficient treatment. This step is different from settling basins, which rely on gravity to remove solids, and it’s not meant for heating or chemical precipitation for nutrient removal.