Abstract: The filtering cell, according to this invention, includes a tank having a base wall and a filter bed supported above the base wall which divides the tank into an upper compartment for receiving a substance to be filtered and a lower compartment for receiving a filtrate. The improved filter pan disclosed in this application has a compound slope, that is, the drainage of the filter bed is towards the center of the filter pan into the drainage channel and also toward the outlet orifice. This compound slope is made possible by the drainage channel also having an incline toward the outlet orifice.