Which of the following is NOT an advantage of rotating biological contactors?

The correct answer highlights that high sludge production is not an advantage of rotating biological contactors (RBCs). In wastewater treatment, one of the goals is to minimize excess sludge generation since high sludge production can lead to increased costs and complications in the management of solid waste.

Unlike some systems that may generate more sludge due to their operational mechanisms, rotating biological contactors are designed to promote efficient microbial growth on their rotating elements, which typically results in lower sludge production compared to other treatment systems. This is beneficial for facilities aiming to operate economically and with lower maintenance in sludge handling.

The other options presented reflect actual advantages of RBCs. Their ability to handle large flows indicates that these systems can effectively treat significant volumes of wastewater, making them suitable for varying scales of operations. Low power requirements also characterize RBCs, as they often rely on the natural aeration brought about by the rotation rather than requiring high energy input. Finally, low operating costs are significant since RBCs generally require less maintenance and fewer resources to operate effectively compared to more complex treatment systems. This combination of features makes RBCs a popular choice in many wastewater treatment applications.