Struvite Precipitation Recycling Of Phosphorus In Wastewater

It is well known that the pollution caused by phosphorus plays key role in the eutrophication of water, whilst we human beings have to face the shortage of phosphorus resource in the forthcoming years. However, conventional processes for removing the superfluous phosphorus from waste water barely rely on biological or chemical approach while regardless of recycle of phosphorus. Therefore, the recycle of phosphorus from waste water is a vital issue which needed to be resolved urgently.In this paper, the mechanism and process of the recovering of phosphorus from waste water based on struvite method were investigated in detail. In addition, the probability of the replacement of magnesium saline by bittern was also carefully examined. In fact, this method was used for the recovering of phosphorus from realistic waste water.(1) Theoretically, the relationship between conditional dissolve product of magnesium phosphate and magnesium hydrate of byproduct and struvite and pH was explored herein. Obviously, both of theoretical computation and experimental result indicate the solubility of struvite were raised with pH value and then declined rapidly, followed by rise slightly. Based upon this result, the contents of several kinds of heavy metal including Ni, Cr and Cd in struvite were determined herein. In fact, the mechanism of the carrying heavy metal was caused by the precipitation of hydrate.(2) The effects of recovering ratio of phosphorus by some other process conditions besides pH value were investigated in detail based on the simulative waste water. Obviously, while the initial content of phosphorus below 50mg/L, the recycle ratio of phosphorus was above 80%; while the initial content of phosphorus was higher than 100 mg/L, the recycle ratio of phosphorus could turn up to a satisfying ratio of 90%. However, the initial content of phosphorus only has a little effect on the remaining phosphorus content between 10 and 18 mg/L of waste water which has been precipitated of struvite. The solubility would be affected by temperature while the recycle ratio of phosphorus might then be influenced. Indeed, the solubility of struvite increased with the raise of temperature, which leads to the recycle ratio of phosphorus decline slightly with the raise of the temperature. Besides, although the solid suspended substance could serve as the crystal core for the separated crystal of struvite, there is only slight effect on the recycle of the phosphorus.(3) In theory, the equation of dissolve product of struvite was deduced, which...