Lowering specific energy consumption (SEC) in reverse osmosis (RO) plants is one of the most important criteria in water treatment industry. The present work focused on best suggested RO pilot plant configurations for minimizing specific energy consumption, finding the best configurations experimentally to recover the water with minimizing salts in permeate side in RO module, study the factors affecting the performance of single and two stage systems, TFC membrane is used in spiral wound module. Brackish water is used as feed solution with different concentrations (2000, 3000, 4000 and 5000 ppm). The operating parameters studied were permeate flux, rejection and SEC. The experimental results showed the permeate concentration increased and water flux decreased with increasing in time from 0 to 60 min if concentrated stream at any ratio recycled to feed vessel. Also, the permeate concentrations increased and flux decreased with increasing in feed concentrations from 2000 to 5000 mg/L. At fixed operational pressure, rising of pressure from 4 to 7 bar extract more flux and permeate concentration decreased, in fixed feed concentration, for single stage operation mode, recycling 50% permeate to the feed makes the best permeate flux and the lowest SEC, for C f = 2000 ppm, Jw = 12.03 LMH and SEC = 0.551 kWh/m3, for the two stage operation mode, recycling 50% of permeate first stage and second one to the feed of second stage system has the best results that average J w = 10.746 and 10.623 LMH for the first stage and second respectively with total SEC = 0.55 kWh/m3.
