Ultrasound enhancement of microfiltration performance for natural organic matter removal

Sonication of water at 1500 W prior to microfiltration showed that a short time (60 s) gave a reduced flux decline. It is suggested that a less potent, smaller molecular form of the natural organic matter (NOM) was produced by sonication. Longer sonication time diminished this beneficial effect. This may be due to the formation of aggregates or compounds that are more readily adsorbed on to the membrane. Where the sonication was preceded by an alum treatment, the flux loss showed a regular decrease with longer sonication time. It is suggested that the effects of sonication on the alum floc and on the floc/NOM interaction may play a critical role in regulating the flux. Where sand was present during sonication at 800 and 1400 W, the cavitational energy was focussed on adsorbed organic material, resulting in more efficient destruction and the formation of compounds that counteracted the flux enhancement.