Studies on scaling of membranes in desalination by direct contact membrane distillation: CaCO3 and mixed CaCO3/CaSO4 systems

Scaling of membranes by CaCO3 and CaSO4–CaCO3 is of considerable concern in membrane desalination processes. It is particularly relevant for porous crossflow hollow fiber-based membrane distillation (MD) processes which can achieve high water recovery and can encounter heavy precipitation of scaling salts. Therefore an analysis of the scaling potential for CaCO3 and mixed CaSO4–CaCO3 systems is presented first in terms of the saturation index profiles throughout the crossflow hollow fiber membrane module as a function of the location in the module for feed solutions resulting from high water recovery. Scaling experiments during DCMD with tap water, CaCO3 and mixed CaSO4/CaCO3 were conducted over a wide range of values of saturation index (SI) (10