A periodic pressure filtration process is evaluated to determine if the process can be used to thicken clay slurries. Current environmental cleanup operations, such as soil washing, result in large volumes of dilute slurries that must be filtered to remove the particles. The soil particles collected during the filtration, if clean, can be returned to the ground. One step in the dewatering and filtering process is thickening the slurry before filtering. The periodic pressure filtration process is one possible process for thickening clay slurries, but no performance data are available for evaluating the process. In this work a one-tube periodic pressure filter process is evaluated by measuring the thickened slurry discharge and filtrate rate while varying the design and operating parameters. The experimental results show that the process can thicken slurries of 1 to 3% inlet mass concentration to about 30 to 40% mass concentration.