What is the term for a condition where clear supernatant is pumped through the sludge blanket of a gravity thickener?

The term that describes the condition where clear supernatant is pumped through the sludge blanket of a gravity thickener is known as "coning." This phenomenon occurs when the movement of liquid through the sludge blanket creates a conical shape as it disrupts the settled solids. As clear water is drawn from the top, it can cause the solids beneath to form a cone shape instead of remaining uniformly distributed.

Understanding coning is crucial for operators overseeing gravity thickeners because it impacts the efficiency of the thickening process and the quality of the sludge. Proper management of flow and the operational parameters can help prevent undesirable coning behavior, ensuring that solids are effectively thickened and that the process runs efficiently.

In contrast, scouring refers to the removal of settled solids due to the flow of liquid, which can lead to increased turbidity in the effluent. Flotation is a different process involving gas bubbles to help separate solids from liquids, particularly with dissolved air flotation systems. Settling pertains to the process where solids naturally aggregate and settle under gravity, different from the interaction occurring in coning. These terms illustrate distinct actions or outcomes in wastewater treatment, with coning specifically highlighting the behavior of supernatant flow through a sludge blanket.