AWWA MTC50241

Cross flusing can be applied in dead-end ultrafiltration systems to improve the efficiency of cleaning and reduce the consumption of chemicals. The efficiency of an air-water, two phase cross flush was compared with a water cross flush, in a horizontal dead-end ultrafiltration system. Crossflushing was more effective when the velocity in the fiber was in the turbulent regime (v=1.6 m/s). No beneficial effect of using a gas-liquid, two phase flow in a horizontal, dead-end ultrafiltration system was observed. This was attributed to the fact that the air:water ratio of the cross flush was too low. A periodic water flush is required to remove residual air bubbles after an air/water cross flush in a horizontal ultrafiltration system, otherwise the accumulation of air bubbles on the surface of the membrane will reduce the effective membrane area for filtration. Includes 8 references, tables, figures.