Effect of air sparging on flux enhancement during tangential flow filtration of degreasing effluent

The favorable effects of air sparging to reduce deposition on the membrane and consequent fouling during membrane separation are studied, first with a model solute (pectin), followed by degreasing effluent from a tannery. Directly injecting air into the feed stream enhances the permeate flux and the performance of the separation process in a rectangular flat sheet tangential flow membrane module. The effects of various operating parameters, namely, gas velocity, membrane surface orientations with respect to the flow direction, transmembrane pressure, cross-flow velocity, and model solute concentration, are quantified. The concentrations of pectin solutions used herein are chosen such that they behave similar to the degreasing effluent in terms of gel layer-type deposition on the membrane surface. Also, there are significant changes in the permeate quality (80 mg/l) by using air sparging in the flow channel which is below Indian discharge standards (250 mg/l). There are appreciable changes in the permeate quality when air sparging is employed compared to membrane separation without aeration. Image analyzing video microscopy is effectively used to precisely measure variation in deposition thicknesses on surface of the membrane as functions of operating parameters. Once the effectiveness of the method is established, the technique is successfully used, with significant flux enhancement, to treat degreasing effluent from a tannery.