| ABSTRACT: Nitrogen and phosphorus are one of the most common pollutants that cause water quality impairments. Comparing with Nitrogen recycling, the period of Phosphorous recycling is very long, and when its concentration is 0．015mg/L, it will cause algae's excessive increase, therefore, controlling phosphorous discharge is a more valid method in order to prevent the water body from contamination. At the same time, phosphorus is not only a essential element that is needed by all the biological cells, but also a raw material that is needed in industry and agriculture production. Therefore, phosphorus recovery from the wastewater is a good strategy in order to realize phosphorous sustainable utilization and change the wastewater into resource. Struvite precipitation process, which can extract and recover phosphorous and nitrogen simultaneously and has the potential use as a fertilizer, has attract more attention. In our country, the research of MAP process is at the beginning.In this paper, the main conditions that influence the struvite precipitation were investigated using simulated wastewater as reacted water, and the environmental and economical profits were evaluated. In single factor experiment, the influence of reaction pH, reacted contact time and initial ammonium concentration on struvite precipitation reaction and the composition of the product were discussed. The influence of molar ratio of three constituted irons and pH on phosphorus recovery efficiency(PRE) were investigated in the struvite precipitation process. Finally, the change of PRE and the component of the product were reviewed in different Ca2+ concentrations.The results indicated, reaction pH, which was been maintained in the range of 9．5～10．0,was good for struvite precipitation, and PRE could reach 50% in this situation; reacted time had less effect on the precipitation reaction, three constituted irons formed nuclear and precipitated rapidly in five minutes, then the removal rate of these three constituted irons changed a little, which maintained steadiness till reacted time was 30 minute; initial ammonium concentration influenced PRE and the component of the precipitate, XRD analysis showed: the precipitate was mainly composed of Mg3(PO4) 2·22H2O when the NH4+:PO43- molar ratios were 1:1, 1．2:1 or 1．6:1．However, the precipitate became the mixture of Mg3 (PO4) 2 22H2O and MgNH4PO4·6H2O when the NH4+:PO43- molar ratio was 2:1．Furthermore, the precipitate was mainly MgNH4PO4·6H2O when the NH4+: PO43- molar ratios were 3:1 and 6:1．Overall, PRE increased from 51．6% to 84．6% with increase of NH4+: PO43- molar ratio from 1:1 to 6:1; higher initial ammonium-N concentration increased purity of the precipitate and further elevate PRE; the results of the test showed that: by maintaining the same conditions of molar ratio of Mg/N/P as 1．4:4:1, reaction pH as 9．5, and reacted time as 30 minutes, PRE reached 94．0%, and increasing Mg/P properly was good for PRE improvement; the diffraction diagram indicated: there was no remarkable change in PRE after adding to Ca2+, the component of precipitates was still struvite when Mg/Ca changed from 1:0．2 to 1:0．5, but when Mg/Ca reached l:0．8,the precipitate showed the character of amorphous substance.
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