Frequently Asked Questions What, exactly, does the baffle do? The liquid in the tank settles into three distinct layers. The bottom layer is sludge, which accumulates between services. The middle level is the clearest effluent, which is directed to the drainage system. The top layer is scum, which is where the bacteria works to break down solids into sludge. The baffle prevents the scum layer from leaving the tank through the outgoing line, which is also located near the top of the tank. Return to FAQ's