Study On Enhanced Remediation Of Cr(Ⅵ) Contaminated Groundwater By Emulsified Oil Reaction Zone

Chromium and chromium compounds as an important industrial raw material,was widely used in electroplating, printing and dyeing, tanning, non-ferrous metalsmelting industry. Unreasonable stacked of chromium residue and chromiumcontaining wastewater discharged arbitrarily, caused serious pollution of soil andgroundwater.Emulsified vegetable oil as a new remediation materials, has shown a broadprospect of application and to be effective in the remediation of contaminatedgroundwater.In this thesis, a series of experiments was conducted to research the enhancedremediation of groundwater Cr(Ⅵ) pollution by emulsified oil reaction zone. Thisthesis mainly studied the distribution and migration of emulsified oil in the aquifer andthe effects on the aquifer permeability; simulation experiment, studied the remediationefficiency of Cr(Ⅵ) in the emulsified oil reaction zone. The experimental resultsindicate:Emulsified oil could migrate a considerable distance under the naturalgroundwater flow when injected into the aquifers and could be trapped in the aquifer.This made advantages to form a stable reaction zone in a large range of aquifer. When5%(m/m) emulsified oil injected into the aquifer, the hydraulic conductivity of aquiferreduced from the initial2.367*10-4m/s to1.547*10-4m/s. And the permeability ofaquifer could restore gradually by injecting water and flushing.Emulsified oil could promote dissimilatory iron reduction of the indigenousmicroorganisms in the aquifer, and generate a large amounts of Fe(II). Cr(Ⅵ) isreduced to Cr(Ⅲ). Emulsified vegetable oil could keep the groundwater weak acidity,and significantly change the Oxidation-Reduction Potential of aquifer.5%(m/m) emulsified oil could form a strong reaction zone in20days after injected into the aquifer. A one-time injection of emulsified oil, can maintain theaquifer a reduction environment for over200days. Cr(Ⅵ) was reduce to Cr(Ⅲ)efficiently and stabilized in aquifer. To add a certain amount of acetic acid andMg(OH)2could enhance the remediation effectiveness of the reaction zone in earlystage, but with a large consumption of raw materials such as Fe(Ⅲ) and organic matter,which resulted an insufficient late stage reaction, shorten the life of reaction zone.In the emulsified oil reaction zone, the cyclic reaction of Fe is exists. Thecontenting of bioavailable Fe(Ⅲ) in Aquifer medium is the key factor that limiting thelife of reaction zone. Eventually, Cr mainly bound to Fe-Mn oxides and organic matter.Cr exists stably in the aquifer medium, and under natural conditions it is difficultly tobe released again. The reaction that Cr bounded to Fe-Mn oxides transform tobounding to organic matter maybe exist.