Which of the following is NOT a method of sludge dewatering?

The correct answer identifies a method that does not pertain specifically to the process of sludge dewatering. A flotation tank is primarily utilized for the separation of solids from liquids by introducing air bubbles, allowing suspended solids to rise to the surface and form a scum layer. While flotation can be part of various solids removal or wastewater treatment processes, it is not a direct method of dewatering sludge.

In contrast, sludge dewatering methods such as plate and frame presses, centrifuges, and drying beds and lagoons are specifically designed to reduce the water content of sludge. Plate and frame presses achieve this by applying pressure to squeeze out moisture. Centrifuges utilize centrifugal force to separate solids from liquids effectively, while drying beds and lagoons rely on evaporation and natural drainage to remove water from sludge.

Understanding the distinctions between these methods is crucial in the context of wastewater management, as it informs the selection of appropriate techniques for handling and reducing sludge volume in treatment facilities.