Optimization of permeate flux produced by solar energy driven membrane distillation process using central composite design approach

Membrane distillation (MD) is considered as a relatively high-energy requirement. To overcome this drawback, it is recommended to couple the MD process with solar energy as the renewable energy source in order to provide heat energy required to optimize its performance to produce permeate flux. In the present work, an original solar energy driven direct contact membrane distillation (DCMD) pilot plant was built and tested under actual weather conditions at Jeddah, KSA, in order to model and optimize permeate flux. The dependency of permeate flux on various operating parameters such as feed temperature (46.6-63.4 degrees C), permeate temperature (6.6-23.4 degrees C), feed flow rate (199-451 L/h) and permeate flow rate (199-451 L/h) was studied by response surface methodology based on central composite design approach. The analysis of variance (ANOVA) confirmed that all independent variables had significant influence on the model (where P-value < 0.05). The high coefficient of determination (R-2 = 0.9644 and R-adj(2) = 0.9261) obtained by ANOVA demonstrated good correlation between experimental and predicted values of the response. The optimized conditions, determined using desirability function, were T-f = 63.4 degrees C, T-p = 6.6 degrees C, Q(f) = 451 L/h and Q(p) = 451 L/h. Under these conditions, the maximum permeate flux of 6.122 kg/m(2).h was achieved, which was close to the predicted value of 6.398 kg/m(2).h.