Major disadvantages to extended aeration?

• A. Simple operation
• B. Small footprint
• C. Expensive, high electrical costs
• D. Low energy costs

Answer: (C)

Extended aeration relies on keeping the mixed liquor aerated for a long time to achieve thorough treatment. That long aeration period means the aerators and blowers run for extended durations, which drives up electricity usage. Energy costs become the major operating expense, making this the main disadvantage of extended aeration. While it can produce stable effluent and low sludge production, those benefits come with higher electrical costs and typically larger equipment needs. The other options describe traits that aren’t true drawbacks for this approach.