Long-term performance of membrane distillation process

The results of the over 3 years' time research on the direct contact membrane distillation applied for production of the demineralised water have been presented. The hydrophobic capillary polypropylene membranes (Accurel PP S6/2) were used in these studies. The inlet temperature of the feed and the distillate was 353 and 293 K, respectively. The membranes were found to be thermally stable, and good separation characteristics was maintained throughout the whole period of the investigations. The SEM observations of the capillary membrane confirmed that their morphology remained unchanged. It was found that water (permeate from reverse osmosis process) did not cause the wetting of the used membranes despite a long-term membrane module exploitation. The precipitation of CaCO3 on the membrane surface was observed when tap water was used directly as a feed. A partial wetting of the membrane was found in this case. The wettability resulted in the increased electrical conductivity of the distillate obtained from 0.9 to 2.5 μS/cm.