The objective of the study presented here was to determine the transformation of phosphorus (P) between different forms in the process of intermittent and continuous aeration. According to this study, aeration, at an air flow rate of 1.0 litre/minute, resulted in an increase in the manure pH of approximately one unit, from 6.5 to 7.5, within 24 h, accompanied by a reduction in soluble ortho-P of 76%. This reduction in soluble P was apparently caused by the chemical precipitation that was indicated by a reduction in organic P and a simultaneous increase in insoluble inorganic P. The analysis of mass balances between the P fractions showed a large transformation of inorganic insoluble P into organic forms during the aeration period, which could overshadow the efficiency of soluble P removal by microbes. Because the manure contained ~73.5% insoluble inorganic P, it is suggested that solid-liquid separation should be performed prior to aeration to increase the efficiency of soluble P removal. In addition, continuous aeration did not show an advantage over intermittent aeration in terms of soluble P removal.