Evaluation of a real-time visualization system for scaling detection during DCMD, and its correlation with wetting.

Abstract A visualization system was designed for a real-time observation of scales during direct contact membrane distillation (DCMD). The system was composed of a MD module, a camera and light sources. Firstly, visibility of the scales with the system and correlation between detected spots and wetting were assessed during the MD process using a polyvinylidene fluoride (PVDF) 0.45 μm membrane. The white spots were observed in the captured images from the visualization system and got broader with the electrical conductivity (EC) increase in permeate. It was verified that the spots indicated the pores blocked by the CaSO 4 scales. The wetting occurred through the white spots if the pressure was applied. Therefore, the high wetting potential area could be identified with the suggested visualization system during the MD operation in real-time. The visualization system was applied to the MD process under different permeate temperatures (20 and 55 °C). The visualization system successfully detected the pore blocking related with different scale formation according to the temperatures at the membrane surface. Graphical abstract Unlabelled Image Highlights • The visualization system was suggested for the detection of the scales in real-time. • The scales in the pores and on the surface were detected using the system. • The suggested system enabled to provide temporal and spatial information on scales. • The different wettability was successfully distinguished by the system. [ABSTRACT FROM AUTHOR]