Scale formation mechanisms and its control by antiscalants in FO membrane under low temperature conditions

Abstract

The performance of forward osmosis (FO) membrane process is generally influenced by the characteristics of the feed and draw solutions. Assuming that FO is applied in cold regions, the temperature of the feed or draw solution may be low, thereby affecting the water productivity and fouling propensity of FO membranes. Unfortunately, little information is available on the capability of FO to low-temperature waters. Accordingly, this study intends to examine the scale formation in FO membrane process under low temperature conditions. Experiments were carried out in a bench-scale experimental setup using flat sheet commercial FO membrane. The feed temperature was fixed at 25°C and the draw solution temperature was varied from 5°C to 25°C. Mechanisms of scale formation under low-temperature conditions were explored. The effectiveness of antiscalant to control scale formation in FO process was also investigated as a function of draw solution temperature. Results showed that the mechanism of scale formation under low-temperature is different from those under room temperature condition. The comparison of morphologies of the crystals on the FO membrane surfaces revealed the different mechanisms of scale control by the antiscalant under different temperatures.