A pump and valve arrangement (201), a dialysis system (10) comprising the pump and valve arrangement 201 and a method of operating a pump and valve arrangement (201). The pump and valve arrangement (201) has a dialyser having a semi-permeable membrane. The pump and valve arrangement (201) delivers dialysis fluid to and from the dialyser (12). The pump and valve arrangement (201) has a control system (450) configured to shuttle dialysis fluid between an inlet pump assembly and the dialyser (12) one or more times so as to agitate the surface of the semi-permeable membrane of the dialyser (12).

A method and apparatus for improved separation and containment of radioactive particulates from liquids by filtration. The improvements are achieved by utilizing more than one stage of filtration to remove radioactive particulates from a fluid. The first stage of filtration is designed for high liquid flowrate, low differential pressure across the filter medium, and reversibility of flow through the medium to facilitate backwashing. The second or more stages of filtration receive the backwash flow and captured particulates from the first stage at a lower flowrate, but at high pressure using a high-pressure pump configured between the stages.

A water treatment system includes a source of inlet water, a prefiltration unit, a feeder, a pump, and a membrane element. The prefiltration unit is in fluid communication with the source and provides a prefiltered water to a prefiltered water line. The feeder is in fluid communication with the prefiltered water line and is positioned downstream of the prefiltration unit. The feeder is designed to deliver a chemical additive to the prefiltered water. The pump is in fluid communication with the prefiltered water line and a permeate flush line, and the pump is designed to increase a flow rate of water in a membrane feed line. The membrane element includes an inlet that is in fluid communication with the pump via the membrane feed line. The membrane element produces a permeate imparted with a first concentration of solutes and a retentate imparted with a second concentration of solutes.