Abstract
This study investigated the effects of an electromagnetic field (EMF) on control of membrane fouling and scaling during desalination of brackish groundwater using a pilot reverse osmosis (RO) skid. The groundwater was primarily CaSO4 type with a total dissolved solids concentration of 5850 mg/L and hardness of 2500 mg/L as CaCO3. Two EMF devices were installed in the pipeline before a cartridge filter and in the RO feed inlet to induce an electric signal of ±150 kHz to the groundwater. The effects of EMF on membrane scaling were evaluated under accelerated conditions, i.e., without pH adjustment and addition of antiscalant. Two-phase experiments were conducted: Phase 1 (376 h) with the EMF devices turned on after 150 h baseline operation; and Phase 2 (753 h) with the EMF devices turned on from the beginning of testing. The EMF significantly reduced membrane scaling and improved RO performance by 38.3% and 14.3% in terms of normalized water permeability decline rate after 150 h and 370 h operation, respectively. Membrane autopsy results indicated that the fouling layer formed under the influence of EMF was loose with a low density and was easily removed by hydraulic flushing.
Highlights
Use of alternative water sources has become a viable solution to augment freshwater supplies.Reverse osmosis (RO) is a prevalent desalination process to treat seawater, reclaimed water, and brackish water [1,2]
The decreasing rate of the water permeability is slower in Phase 2 (P2) than in Phase 1 (P1) and the difference increases with the operation time, indicating that the electromagnetic field (EMF) devices retarded the fouling and scaling on the reverse osmosis (RO) membrane surface
This study investigated the effect of electromagnetic field (EMF) on the control of membrane colloidal fouling and scaling during brackish groundwater desalination
Summary
Use of alternative water sources has become a viable solution to augment freshwater supplies.Reverse osmosis (RO) is a prevalent desalination process to treat seawater, reclaimed water, and brackish water [1,2]. One of the limitations of the RO process is membrane fouling and scaling caused by accumulation and precipitation of the rejected constituents. Membrane autopsy using scanning electron microscopy, energy dispersive X-ray microanalysis, X-ray diffraction, and other advanced analytical methods indicated membrane fouling and scaling are primarily caused by precipitation of colloidal particles, organic matter, sparingly soluble salts such as silica, calcium sulfate, calcium carbonate, barium sulfate, calcium phosphate, and calcium fluoride after water is filtered through the membrane under high hydraulic pressure [3,4,5,6]. Several methods have been developed to control membrane fouling and scaling, such as pretreatment of feedwater, membrane monitoring and cleaning, development of new anti-fouling membranes, and optimization of operating conditions [7,8,9,10]
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