Treatment Of Riverside Groundwater Pollution By Iron Powder-Activated Carbon-Zeolite

The Groundwater source near the river is one of the important water supplying sources in China.In recent years,with the development of social economy,some groundwater near the river has been polluted.Permeable reaction barrier technology,which is an efficient,economical and stable method of in situ groundwater restoration,has become a hot topic in groundwater pollution treatment.In this paper,the remediation of pollution of hexavalent chromium,ammonia nitrogen and organic matter by permeable reaction barrier fillers was studied by indoor simulation.Through analysis of results from batch experiments and column experiments?operated for 30days?,the selected iron powder+activated carbon+artificial zeolite combination fillers were used for small-scale pilot experiments.The small-scale polit experimental device series were operated for 91 days under the condition that the concentration of hexavalent chromium was10/L and ammonia was 20 mg/L and 100mg/L respectively.The morphology,species and content of the fillings were determined by scanning electron microscopy and energy dispersive spectrometer.Experimental results show that:?1?Zero-valent iron powder fillers can remove hexavalent chromium effectively in contaminated liquid with a maximum removal rate of 84.2%.The reaction mechanism is mainly the oxidation reduction reaction between Zero-valent iron and hexavalent chromium.Zero-valent iron and hydrogen ion and ferrous ions from iron corrosion in water react with hexavalent chromium to produce sediments such as trivalent chromium and trivalent iron.Trivalent chromium is less toxic and can be removed from water in the form of precipitation.?2?The synthesis of synthetic zeolite is mainly divided into solid phase and liquid phase.The synthetic zeolite,whose formula is Na₂O·Al₂O₃·xSiO₂·yH₂O,removes ammonia from contaminated fluids with a maximum removal rate of 87.7%.The mechanism of removal of ammonia and nitrogen by artificial zeolite is mainly ion exchange between sodium ions and ammonia ions.When zeolite ion exchange agent is close to saturated capacity,the removal efficiency of ammonia and nitrogen begins to decrease rapidly.Sodium chloride can be used to regenerate zeolite.?3?The effect of active carbon filling on COD removal in contaminated liquid is better and the best removal rate of COD was 54.9%.Activated carbon could adsorb low molecular organic compounds in the contaminated liquid and reduce the COD concentration.Activated carbon has fast and stable adsorption of organic matter.Its service life is higher than that of artificial zeolite filler.?4?The redox reaction between zero-valent iron and hexavalent chromium consume hydrogen ion,and the ion exchange between zeolite and ammonia nitrogen increases hydroxyl ions in aqueous solution.The pH value of the experimental water increased continuously,exceeding 9.0.Subsequent treatment of water samples requires pH regulation.This study is applicable to the pretreatment of the underground water source near the river,which contains mixed pollution of hexavalent chromium,ammonia and organic matter.It is simple,economical and efficient to repair groundwater in situ by placing iron-carbon-synthetic zeolite filler in permeable reaction barrier.This study can provide some data reference for the repair of the groundwater in the small towns and rural areas.The innovation of this paper lies in the use of combined permeable reaction barrier filler to treat groundwater composite pollution.