A water treatment device for purifying process water by filtration comprising a housing containing a filter media, having a bottom gravel bed and an upper silica bed, and a fluidizer for backwashing the filter media. Process water is tangentially introduced and caused to swirl in the housing above a filter media, before passing downwards through silica and gravel beds. The swirling increases the through capacity of the treatment device and reduces the amount of particles that would otherwise become imbedded in the filter media. Backwashing is accomplished by forcing fluid, through first and second components of the fluidizer, into the filter media. The first component is a channel formed in the manifold which provides backwash fluid to the bottom of the gravel bed. The second component provides backwash fluid at the gravel bed—silica bed interface by a series of radially spaced fluidizer arms. The fluidizer manifold provides complete fluidization of the filter media such that the filter media does not have no flow, or low flow, areas.