Two new crystallizers with internal circulation of suspension driven by a jet pump device were constructed. The jet pump feeding nozzle was provided with the compressed air stream instead of clear mother soln. The feeding nozzle of the jet pump was located either in the crystallizer bottom or below free surface of the clarified mother liquor. The crystallizers were tested by crystn. of struvite during its pptn. from alk. aq. soln. of MgCl(2) and NH(4)H(2)PO(4). The struvite crystals produced were well shaped (size 25-35 mu m). The removal of phosphate ions from the soln. was about 98%.