Incipient calcium carbonate scaling of desalination membranes in narrow channels with spacers—experimental insights

Incipient crystallization of calcium carbonate on desalination membranes: dead-end filtration with agitation

“…From the measured number concentration of feed bulk-particles in some tests (73D and 78D, Table 2), it is concluded that this concentration is relatively small and (if all such particles were deposited) would make insignificant direct contribution to the total scale-particle mass measured on the membrane. Indeed, a fair estimate of the deposition rate of bulk CaCO 3 particles on the membrane surface can be obtained using the approach described elsewhere [16]. For a typical range of deposition coefficients k D = 10 −5 to 10 −3 cm/s (rather conservative for order of magnitude calculations) and using the average value 0.10 mg/L for particle mass concentration in the feed-fluid (data for tests no.…”

“…From the experimental standpoint, at the allowable in desalination plants quite low bulk supersaturation ratio S of the aforementioned salts, there is uncertainty on whether an "induction period" of membrane scaling exists [16], as well as on how, and at which rate, the scale-particles initially develop (or deposit) and then grow on a "clean" desalination membrane. Most of the work on desalination membrane scaling has been carried out at relatively high supersaturations and/or for experimentation times beyond the initial phase of crystal generation, deposition, and growth on a virgin membrane surface [17][18][19].…”

“…fluid turbidity, conductivity, and Ca 2+ concentration) or process parameters (e.g. flux decline) [17][18][19][20], which lack the required sensitivity [16] to observe the initially sparsely distributed micron-size scale particles on the membrane. At the theoretical level, our ability to predict true incipient scaling under realistic conditions is mainly hampered by two factors; i.e.…”

“…Moreover, tests with the filtration cell under agitation are more convenient and less time-consuming than those in cross-flow desalination systems, for detailed experimental observations and determination of model parameters; such data are useful to validate and/or improve currently used theoretical models. However, it should be stressed that the more laborious cross-flow tests are still needed to obtain more realistic data on incipient membrane scaling [16] for comparison with the dead-end cell results. In view of the aforementioned state of the art, the scope of this work is to study experimentally incipient crystallization of calcium carbonate on desalination membranes, under well-controlled conditions of small initial supersaturations, in a dead-end cell with fluid agitation.…”

Foulant characterization and distribution in spiral wound reverse osmosis membranes from different pressure vessels

“…In particular, research related to the actual transport and hydrodynamic phenomena of membrane foulants inside SWM elements and pressure vessels has been insufficient and only evaluated by means of modeling tools [4,5]. Although some researchers have reported on inorganic scaling inside SWM elements based on experimental results obtained from microscopy and 3D computational fluid dynamics (CFD) [6,7], interactions between organic contaminants and the membrane surface of SWM elements remain uncertain. In summary, a better understanding of the transport and distribution of membrane foulants inside the SWM elements is of primary importance in order to improve the operation of SWM-based water treatment plants.…”