Section Sanitary Engineering, Department of Water Management, Delft University of Technology, Stevinweg 1, 2628CN Delft, The Netherlands.
Section Sanitary Engineering, Department of Water Management, Delft University of Technology, Stevinweg 1, 2628CN Delft, The Netherlands.
Bioresour Technol. 2016 Oct;218:1151-6. doi: 10.1016/j.biortech.2016.07.088. Epub 2016 Jul 21.
The results in this study show that struvite was formed in the digester at pH 7.7 due to the magnesium naturally present and the released ammonia and phosphate, resulting in low phosphate concentration in the digester. Apparently the digester already provided proper conditions for struvite formation. Under the brackish condition, the estimated thermodynamic solubility product and enthalpy change of struvite formation were 10(-13.06) and 25.7kJmol(-1), respectively. The average crystal size under marine/brackish condition decreased with pH, but increased with temperature. X-ray diffraction measurements indicate struvite (NH4MgPO4·6H2O) and dittmarite (NH4MgPO4·H2O) were predominant phosphorus species produced in filtrates of the digester. However, struvite and newberyite (HMgPO4·3H2O) were the predominant species precipitated from synthetic brackish waters after dosing MgCl2. It is pronounced that (waste)water characteristics played also an important role on the nature of phosphate precipitates. Under high NH4(+) condition, phosphorus precipitates containing ammonia were dominant, compared to other amorphous phosphates.
本研究结果表明，由于天然存在的镁以及释放出的氨和磷酸盐，在 pH 值为 7.7 的消化器中形成了鸟粪石，导致消化器中的磷酸盐浓度较低。显然，消化器已经为鸟粪石的形成提供了适当的条件。在咸水环境下，鸟粪石形成的估计热力学溶解度积和焓变分别为 10(-13.06)和 25.7kJmol(-1)。在海洋/咸水环境下，平均晶体尺寸随 pH 值降低而减小，但随温度升高而增大。X 射线衍射测量表明，在消化器滤液中主要生成的磷物种是鸟粪石（NH4MgPO4·6H2O）和 dittmarite（NH4MgPO4·H2O）。然而，在投加 MgCl2 后，从合成的咸水中沉淀出的主要物质是鸟粪石和新伯雷石（HMgPO4·3H2O）。可以明显看出，（废水）特性对磷沉淀物的性质也起着重要作用。在高 NH4(+)条件下，含氨的磷沉淀物占主导地位，而其他无定形磷酸盐则较少。
