The effect of aeration on phosphorus removal from swine manure under five temperature regimes, 5, 10, 15, 20, and 25 degrees C, was investigated. The effects of pH and volatile fatty acids (VFAs) levels on soluble ortho-P in the manure were also examined. Results indicated that manure pH was the dominant factor influencing the levels of soluble ortho-P in the manure. Two different mechanisms that effected pH change were identified. A rapid rise in pH due to aeration caused a rapid decline in manure soluble ortho- P. It was concluded that besides any phosphorus immobilization/release by the microbial biomass, the VFAs levels in the manure significantly explained (R2 = 0.83) the biochemical precipitation/dissolution of ortho-P. Temperature affected soluble ortho-P status only in extended aeration. High manure temperatures reduced aeration efficiency but promoted production of VFAs, which led to the release of ortho-P previously precipitated due to the pH decrease. This may potentially reduce the efficiency of removing orthophosphates by subsequent solids-liquid separation treatments.