Study On Reduction Of Nitrate From Groundwater With Sponge Iron As The Reactive Media In Permeable Reactive Barrier

Nitrate pollution in groundwater is now one of the most important environmental problems all over the world, so the restoration of it has become an urgent affair. In this thesis, the status, sources and detrimental effects of nitrate pollution were summarized. Meanwhile, present remediation methods, such as physicochemical method, biologic method, chemical method and permeable reactive barrier technology were analyzed and compared. The permeable reactive barrier is a comparatively promising technology for in-situ groundwater remediation, thus experimental studies on the removal nitrate from groundwater were carried out with sponge iron as the reactive media.In this paper, a series of single-factor static experiments were conducted. Furthermore, the surface chemistry characteristics of sponge iron were analyzed systematically by Scan Electron Microscope (SEM) and X-Ray Diffraction (XRD). Besides, dynamic experiments under various reactive parameters, dynamic experiments with mixture of sponge iron and granule activated carbon and dynamic experiments combining permeable reactive barrier with electrokinetic were processed in this research.The results of the static experiments showed that low pH, smaller particle size of sponge iron, the addition of buffer solution and manganese sand, and the pretreatment of sponge iron with diluted hydrochloric acid were all favorable to the reduction of nitrate by per g sponge iron. After general consideration, the optimal reactive parameters include pH=7～8, diameter 1.0～3.0mm, sponge iron:manganese sand=10:1 and pretreatment of sponge iron with diluted acid. The nitrate reduced by per g sponge iron decreased as more sponge iron was added, but the total amount of reduced nitrate increased. When nitrate concentration range is 11～442mg/L, nitrate reduced by per g sponge iron gradually increased. However, the increase rate of...