Combined standing and propagating wave modes have previously been successfully used by the authors for simultaneous agglomeration and transportation of small particles suspended in still water. The present study of this method with flowing water, using a 120×350×13mm 3 agglomerator, confirmed that the proposed method is applicable with suspended SiO 2 particles of varying size. The process was found to be most efficient at flow rates below a certain threshold, which varies with particle size. This threshold was found to be 5ml/s for a particle size of 7.9μm at an ultrasonic frequency of 2MHz corresponding to 0.74mm wavelength. The existence of a maximum particle transport velocity was demonstrated.