Chemical-free scale inhibition method for seawater reverse osmosis membrane process: Air micro-nano bubbles

Abstract

One of the major problems of seawater reverse osmosis (SWRO) process is the formation of inorganic scales (calcium carbonate, CaCO3) and calcium sulfate, CaSO4)) on the membrane surface, which degrades the filtration performance. Antiscalants have been applied to SWRO plants to overcome the scaling problem. In this study, we used the air micro-nano bubbles (MNBs) as a chemical-free scale inhibition method to improve the overall membrane performance in the comparison with the commercially available antiscalants. During four days of continuous experiments with MNBs, the permeate fluxes declined to 86.5(0.4)% and 83.0(0.5)% with CaCO3 and CaSO4 containing feed solutions, respectively. These values were higher than those obtained with the use of antiscalants in the feed water (CaCO3–63.5(0.4)% and CaSO4–55.8(1.0)%). Membrane fouling characterization results showed that the MNBs efficiently controlled the scaling development on the membrane surface without any chemical addition.