Phosphorus transformations in swine manure during continuous and intermittent aeration processes
The work 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 airflow rate of 1.0 L/min, resulted 
in an increase in the manure pH of about one unit, from 6.5 to 7.5, within 24 hours, 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 about 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.