Fluid processing apparatus

Described are fluid processing devices primarily intended for filtration but which devices may also be used for dispensing or sparging liquids and gases into a body of fluid medium. According to the method of using the disclosed devices, fluid medium to be filtered is caused to flow over the active filtering surfaces of a filter medium, such as by rotating the filter element in the fluid medium, while the fluid medium is simultaneously caused to pass through the filter element. At predetermined intervals the fluid medium flow through the filter is reversed or backpulsed.