The article is about "membrane scaling" which is a major challenge in the water treatment of RO.
Figure 1: SEM image of a virgin (new) RO membrane that has not been scaledFigure 2: SEM image of a RO membrane that has been scaled
Membrane scaling is when one or more sparingly soluble salts (e.g., calcium carbonate, calcium phosphate, etc.) precipitate and form a dense layer on the membrane surface in reverse osmosis (RO) applications.[1] Figures 1 and 2 show scanning electron microscopy (SEM) images of the RO membrane surface without and with scaling, respectively. Membrane scaling, like other types of membrane fouling, increases energy costs due to higher operating pressure, and reduces permeate water production.[2] Furthermore, scaling may damage and shorten the lifetime of membranes due to frequent membrane cleanings[3] and therefore it is a major operational challenge in RO applications.
Membrane scaling can occur when sparingly soluble salts in RO concentrate become supersaturated, meaning their concentrations exceed their equilibrium (solubility) levels. In RO processes, the increased concentration of sparingly soluble salts in the concentrate is primarily caused by the withdrawal of permeate water from the feedwater. The ratio of permeate water to feedwater is known as recovery which is directly related to membrane scaling. Recovery needs to be as high as possible in RO installations to minimize specific energy consumption. However, at high recovery rates, the concentration of sparingly soluble salts in the concentrate can increase dramatically. For example, for 80% and 90% recovery, the concentration of salts in the concentrate can reach 5 and 10 times their concentration in the feedwater, respectively. If the calcium and phosphate concentrations in the RO feedwater are 200 mg/L and 5 mg/L, respectively, the concentrations in the RO concentrate will be 1000 mg/L and 50 mg/L at 90% recovery, exceeding the calcium phosphate solubility limit and resulting in calcium phosphate scaling.
It is important to note that membrane scaling is not only dependent on supersaturation but also on crystallization kinetics, i.e., nucleation and crystal growth.
^Lee, S.; Lee, C.H. (2005-03-01). "Scale formation in NF/RO: mechanism and control". Water Science and Technology. 51 (6–7): 267–275. doi:10.2166/wst.2005.0646. ISSN 0273-1223. PMID 16003986.
^Alshami, Ali; Taylor, Trevor; Ismail, Nadhem; Buelke, Chris; Schultz, Ligia (2021-12-15). "RO system scaling with focus on the concentrate line: Current challenges and potential solutions". Desalination. 520: 115370. Bibcode:2021Desal.52015370A. doi:10.1016/j.desal.2021.115370. ISSN 0011-9164. S2CID 244199653.
^Kucera, Jane (2010-04-05), Amjad, Zahid (ed.), "Reverse Osmosis Membrane Fouling Control", The Science and Technology of Industrial Water Treatment, CRC Press, pp. 247–270, doi:10.1201/9781420071450-c13, ISBN 978-1-4200-7144-3, retrieved 2022-02-12
Membranescaling is when one or more sparingly soluble salts (e.g., calcium carbonate, calcium phosphate, etc.) precipitate and form a dense layer on the...
the membrane between 1.5 and 3 times before it is released as a concentrate. High velocity protects against membranescaling and allows membrane cleaning...
desalination plants, antiscalants are vital for preventing scale formation on membrane surfaces. Scaling can severely impair the efficiency of these processes...
particles. Membranes can be generally classified into synthetic membranes and biological membranes. Biological membranes include cell membranes (outer coverings...
Membrane fouling is a process whereby a solution or a particle is deposited on a membrane surface or in membrane pores in a processes such as in a membrane...
Membrane bioreactors are combinations of membrane processes like microfiltration or ultrafiltration with a biological wastewater treatment process, the...
An artificial membrane, or synthetic membrane, is a synthetically created membrane which is usually intended for separation purposes in laboratory or in...
Membrane technology encompasses the scientific processes used in the construction and application of membranes. Membranes are used to facilitate the transport...
Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of...
membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells. The cell membranes of...
Mucous membrane pemphigoid is a rare chronic autoimmune subepithelial blistering disease characterized by erosive lesions of the mucous membranes and skin...
eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate...
This eliminates corrosion and scaling and allows large-scale cost efficient production. Typical applications of membrane distillation are: Seawater desalination...
Scaling and root planing, also known as conventional periodontal therapy, non-surgical periodontal therapy or deep cleaning, is a procedure involving...
characterized by itching in the ear, malodorous discharge, inflammation, pruritus, scaling, and severe discomfort or ear pain. The mycosis results in inflammation...
cell contains approximately 270 million hemoglobin molecules. The cell membrane is composed of proteins and lipids, and this structure provides properties...
Membrane proteins are common proteins that are part of, or interact with, biological membranes. Membrane proteins fall into several broad categories depending...
in New Zealand, but mining of the Foulden Maar deposits on an industrial scale, for conversion to animal feed, has drawn strong opposition. Diatomaceous...
by synthetic membranes made from polymers such as polyamide or cellulose acetate, or from ceramic materials. While polymeric membranes are economical...
Willinger and Steven M. Stanley (Jan. 6, 2009), "The Key Role of the Surface Membrane in Why Gastropod Nacre Grows in Towers"; Proceedings of the National Academy...
Ankylosaurs is constructed of bone; crocodiles have bony scutes and horny scales. Since exoskeletons are rigid, they present some limits to growth. Organisms...
of N- and C-termini of membrane-spanning polypeptide chain with respect to the inner or outer sides of the biological membrane occupied by the protein...
variety of membrane filtration in which forces such as pressure or concentration gradients lead to a separation through a semipermeable membrane. Suspended...
Global Information
