Zero liquid discharge water treatment system and method

A treatment system (10) includes a feed source (12), a first treatment unit (16) for separating a feed into a first product and a concentrated feed containing less than about 7% total dissolved solids, and a membrane distillation unit (18) for separating the concentrated feed into a second product and a superconcentrated feed containing at least about 14% total dissolved solids. The membrane distillation unit includes hollow fiber membranes (44) having inner bores for receiving the concentrated feed and membrane walls for allowing vapor transmission of distillate. A method includes delivering feed to a first treatment unit where it is separated into first product and concentrated feed streams; delivering the concentrated feed to internal bores of hollow fiber membranes where it is separated into second product and superconcentrated feed streams as vapor passes across the hollow fiber membranes; delivering the superconcentrated feed to a liquid removal unit; and collecting the first and second product streams.