Abstract: A system for treating a mixture, the mixture including drilling fluid and solid material, the system including a container with an inlet for the introduction of the mixture into the container, a solids outlet, and a fluid outlet for drilling fluid to exit the container, at least one rotatable screen assembly rotatably mounted within the container and including at least one screen for screening the mixture and interior structure for receiving separated drilling fluid from the at least one screen, and apparatus in fluid communication with the interior structure for receiving separated drilling fluid therefrom and transmitting the separated drilling fluid to the fluid outlet of the container. This abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure and is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims, 37 C.F.R. 1.