零价铁原位控制底泥磷释放及联合磁性分离除磷技术

水体富营养化是常见的世界性水体生态系统障碍问题之一,给人类生产、生活造成了广泛而严重的影响,同时也是造成世界各地结构性缺水的重要原因之一。底泥磷释放是水体富营养化的重要原因,但目前常用的控磷技术往往成本较高,内源磷再释放风险仍然较大。该研究按铁-泥质量比1.00%、3.33%、5.00%、10.00%,分别向富磷底泥投加的铁粉来模拟零价铁控磷过程,通过分析3、7、14、21、28、35d内底泥磷形态的变化趋势,研究零价铁控磷过程及磁性分离除磷技术的应用前景。结果表明:底泥中水溶性磷、弱结合态磷是水体磷元素的主要来源,零价铁对底泥中高生物活性的弱吸附态磷(NH4Cl-P)去除率最高可达75%,对水溶性磷的去除率可达90%以上,向富磷底泥投加零价铁能够原位富集、降低内源磷生物有效性,阻断底泥向水体释磷的过程;零价铁原位控制底泥磷释放主要依赖于零价铁氧化形成的铁离子和铁氧化物与磷酸根的沉淀和共沉淀过程,加入零价铁后水溶性磷和弱结合态磷主要向铁结合态(Fe-P)转化,联合外加磁场后大部分可随铁粉拔出,最终达到安全高效地去除水体和底泥表层中高生物有效性磷的目的。该方法可以有效解决挖掘清淤、疏浚等控磷方法高成本、易反复的问题,为高效原位治理水体富营养化,保障湖泊、水库生态环境安全提供有价值的技术方法。

A Technique on In-Situ Control of Phosphorous Release in the Sediment with Zero Valent Iron Treatment and Phosphorous Removal Together with the Magnetic Separation

Eutrophication of water bodies is one of the common obstacles to water ecosystems worldwide. This has caused serious and extensive impacts on human production and living. Internal phosphorus(P) release from the sediment is an important cause of eutrophication of water bodies. However, conventional P-control techniques are often costly and the risks of endogenous P re-release are still difficult to be controlled. In this study, iron powder were added to the P-rich sediment by 1.00%, 3.33%, 5.00%, 10.00% respectively to simulate the process of zero valent iron(ZVI) P control. According to the change of the internal P in 3, 7, 14, 21, 28 and 35 d, the mechanism of zero valent iron(ZVI) P control and the application prospects of the magnetic separation and the P removal technology were clarified. The results showed that water-soluble P and NH4Cl-P in the sediment were the major sources of P in water bodies. The removal rates of NH4Cl-P and soluble P by the ZVI reached 75% and 90%, respectively. The addition of the ZVI to the P-rich sediment not only reduced the bioavailability of endogenous P, but also blocked the process of the P release from the sediment in situ. This process depended mainly on the precipitation and coprecipitation of the iron oxidation and the iron oxides with phosphate. After the addition of the ZVI, the water-soluble P and NH4Cl-P were mainly transferred to the iron-bound P(Fe-P). Most of P was pulled out with the iron powder in the combination with the external magnetic field. Finally, the bioavailability P in the surface sediment layer and water bodies can be safely and efficiently removed. This method can effectively solve these problems of high cost and easy repetition of P control methods, such as excavation and dredging. Our study will provide a promising technique for the efficient in-situ treatment in the eutrophication of water bodies to ensure the ecological security of lakes and reservoirs.