A comparative study of an integrated hybrid membrane - based system with an earlier locally designed RO unit, such system comprises of Nanofiltration (NF), Reverse osmosis (RO) and Membrane Distillation (MD) subsystems. The comparison is essentially based on using the NF technique in pretreatment section, while the MD was contributed to concentrate the two brine streams from both NF and RO. The proposed system was economically evaluated and compared with the RO unit.