The present invention is directed toward a multi-pass hyperfiltration system (38) including at least two passes (42,44) of spiral wound modules positioned in series along a fluid pathway; including: a first pass is located upstream along the fluid pathway with respect to a second pass such that permeate from the first pass is directed along the fluid pathway (40) to the second pass, and each pass comprises a pressure vessel enclosing at least one spiral wound module, each module including at least one hyper-filtration membrane envelop and feed spacer sheet wound about a permeate collection tube, wherein the system is characterized by the first pass comprising a spiral wound module including a feed spacer sheet having a thickness greater 0.65 mm and the second pass comprising a spiral wound module including a feed spacer sheet having a thickness less than 0.65 mm.