Anditya Rahardianto, Wen-Yi Shih, Ron-Wai Lee and Yoram Cohen, "Diagnostic characterization of gypsum scale formation and control in RO membrane desalination of brackish water," Journal of Membrane Science, 279, 655-668 (2006).

Wen-Yi Shih, Anditya Rahardianto, Ron-Wai Lee, Yoram Cohen, Morphometric characterization of calcium sulfate dihydrate (gypsum) scale on reverse osmosis membranes, Journal of Membrane Science 252 (2005) 253–263.

Introduction Meeting water demands has become an increasingly challenging task in various regions around the world due to population growth coupled with dwindling water resources and in many cases increased salinity of potable groundwater and surface water sources. At the same time, the emergence of low-pressure reverse osmosis (RO) and nanofiltration (NF) membranes has sparked considerable interests in membrane desalination as a potentially cost-effective strategy for treatment and desalination and of brackish groundwater and high salinity inland water sources. Such membranes provide high salt rejection (>95%) and flux at remarkably low operating pressures (~100-400 psi). However, in order to ensure efficient and cost-effective desalination with such membrane processes, one must combat membrane fouling and scaling while striving to minimize the volume of concentrate (brine) generated to enable operation at a reasonable level of product water recovery.

In order to better understand the development of mineral sale and design effective scale mitigation strategies, diagnostic approaches are being developed to assess mineral scale development in RO desalting and to quantify the impact of scale on flux decline and antiscalant effectiveness.  In initial studies gypsum has been selected as a model scalant given the greater difficulty in mitigating gypsum scaling relative to other common mineral salt scalants (e.g., calcium carbonate). Diagnostic methods developed at the WaTeR center include high resolution optical imaging along with digital image analysis as well as flux decline studies to characterize surface scale coverage. Diagnostic studies are carried out in a dual-cell plate-and-frame RO system as well as in spiral-wound membrane elements. In order to compare membrane scaling propensity and antiscalant effectiveness, the degree of mineral salt scaling is being compared at the same level of initial surface salt saturation index.