Optimization of Operating Conditions to Reduce the Effect of Concentration Polarization on the Performance of Direct Osmosis Process

The need for freshwater is rising rapidly, and fresh water resources cannot meet all human needs. People's access to freshwater is now diminishing with the increasing population and expansion of cities. Accordingly the desalination of sea water has become increasingly important and selection and development of more efficient and cost-effective desalting process is a necessity. The present study was designed to optimize the operating conditions to reduce the effect of external concentration polarization on the performance of direct osmotic process. Due to the number and variety of parameters affecting the amount of water flowing through direct membranes and also with the aim of reducing the number of experiments and costs, the Taguchi experimental design method was used. The structure of membranes was investigated using scanning electron microscopy (SEM). The best performance of direct membrane was observed in membrane No. 1 with test conditions, concentration of molar salt solution, pressure head of 2 psi and pH = 9. In this condition, the flow rate of the flow through the direct osmosis membrane was 36.42 L/m2.h. The highest flux of salt passing through direct membranes was 26.11gr/m2.hr in test conditions and with the concentration of molar salt solution, the pressure head of 2 psi and pH =9. By optimizing the operation conditions, 55.51 perecent increase in the water flux was observed