A water desalination system is provided with 9 reverse osmosis membranes then operated under standard conditions. Feed flow rate 10m3/h, Feed concentration 3000ppm The membranes must be arranged in three vessels, where each vessel contains three membranes 1. Suggest two water desalination scheme where the first one is used to improve the quality of water production while the second one is aimed to increase the water productivity 2. calculate the concentration and flow rate of permeate and brine stream for each case