Effectiveness and mechanisms of electromagnetic field on reverse osmosis membrane scaling control during brackish groundwater desalination

Abstract

This study investigated the effectiveness and mechanisms of electromagnetic field (EMF) on reverse osmosis (RO) membrane scaling control during brackish groundwater desalination. Pilot-scale experiments were conducted with different types of groundwater and two configurations of RO skid operated each for 30 days and 55 days without any other pretreatment. The testing results demonstrated EMF was effective for scaling control under typical RO operating conditions. The EMF significantly enhanced the performance of the RO system by reducing membrane scaling, changing the nature of the formed scales, and decreasing the decline rate of the normalized water permeability. In addition, EMF treatment effectively removed the pre-formed scales and precipitates in water pipelines and tanks but had limited efficacy on removing the pre-formed scales on the RO membranes. Membrane autopsy showed that the scales formed on the membrane surface under the influence of EMF were soft and powdery, being easily removed by water rinsing. The mechanisms of the EMF on RO membrane were discussed, and the dominant mechanism was the magnetohydrodynamic effect. This is the first study that demonstrated the EMF as a chemical-free and effective alternative to control membrane scaling and maintain RO performance during brackish groundwater desalination with discussions on detailed mechanisms and perspectives.