Methods and apparatus for separating solid particles from a fluid. One preferred embodiment includes a tank for settling particles out of the fluid, a conical chamber at the bottom of the tank, an outlet connected to conical chamber, and a conical auger within the conical chamber. The tank may have a tangential inlet that creates a fluid circulation that exerts a centrifugal force on the solid particles to increase the settling of particles out of the fluid. The tank may have a static spiral on the inner wall that helps small particles coalesce into larger particles that settle faster out of the fluid. The fluid content of the solids removed from the tank may be controlled by varying the rotational speed of the conical auger. The rotational speed of the conical auger may be varied depending on the torque required to rotate the conical auger.