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This study investigates the impact of air sparging and the systemconfiguration on the permeate flux in a submerged hollow fiber membrane system. Thestudy was aimed at establishing the magnitude of the contribution from single phasecross-flow, dual phase cross-flow (air sparged), and air slug induced physical contactbetween the membrane fibers on the resulting permeate flux. The bench scale submerged membrane system used in the study consisted of a constant vacuum system (site vacuum line, vacuum regulator,two vacuum equilibration chambers), a permeate collection and measurement system(digital scale and data logger), a submerged membrane system (membrane tank, baffleand membrane module), and an air sparging system (air line, air flow controller,peripheral and central aerators). All experiments were performed at a constant transmembranepressure and the permeate flux was monitored overt time. The results indicate that single phase bulk cross-flow does not significantly contribute tomaintaining a high permeate flux in a submerged hollow fiber membrane system. On theother hand, the interactions between sparged air bubbles and the membrane fiberssignificantly contribute to maintaining a high permeate flux. The physical contactbetween the membrane fibers also significantly contributes to maintaining a highpermeate flux.The reduction in the permeate flux over time could be characterized by an initial shortperiod of fast permeate flux decline, followed by a longer period of slower permeate fluxdecline for all experimental conditions investigated. The hydrodynamic conditions andthe system configuration had a significant impact on the pseudo-steady state permeateflux. The pseudo steady state permeate flux that could be maintained in an air-spargedsystem was 20 to 60% higher that which could be maintained without air sparging. Bypromoting the physical contact between membrane fibers, it was possible to furtherincrease the pseudo steady state permeate flux by 10 to 20%. The pseudo steady statepermeate flux increased with the extent of air sparging. However, a plateau was observedabove which an incremental increase in air sparging intensity was not accompanied by anincrease in the pseudo steady state permeate flux. The physical contact between themembrane fibers enhances the permeate flux by eroding the foulant layer that forms on amembrane surface. Includes 6 references, table, figures.

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Edition: Vol. - No. Published: 11/15/2004 Number of Pages: 11File Size: 1 file , 990 KB