PERFORMANCES OF REVERSE OSMOSIS AND NANOFILTRATION IN DESALINATION OF RIVER BRACKISH WATER

As many countries in the world, Morocco is facing problems in the supply of water due to an increasing demand and decrease of conventional resources. To face the problems, Morocco proceeded since a long time to use other non conventional water resources such as wastewater reuse or desalinating water. The desalination option which was limited to south and coasts extends more and more towards the central regions.

Mrirt is among the north cities where a construction of desalination plant is expected soon. The city is far from the coast and the water to be treated is slightly brackish. The city already has a standard treatment plant of drinking water. The National Office of Electricity and Drinking Water and Ibn Tofail University decided to conduct this study to compare the performances of Reverse Osmosis and Nano filtration technologies.

The experiments are conducted using pilot plants and various commercial membranes such as BW30LE4040, NF90 and NF270. Several parameters were examined in order to optimize the system performance, including operating pressure, flux, system recovery, salt rejection and specific energy consumption (SEC).

The obtained results showed that the experiment results appear to be compatible with those obtained by the software prediction.

The experiment results at 10 bars of feed pressure, for BW30 the values of recovery rate is 28% and 0.95 kwh/m3of energy consumption. For NF90, the recovery rate is 30% and 0.75 kwh/m3 of energy. But in the predict results, and under the same of the operating conditions pilot plant, the values of energy consumption are 0.91 of BW30 and 0.70 of NF90.

Thus, the prediction software results shows that the maximum recovery rate can be achieved to 85% at 20 l/h/m2 of average flux, andthe operating pressure needed to run the RO membrane is significantly higher (14, 6 bar as compared to 9, 90 bar) than the NF membrane.