Experimental Studies On PRB Repair Technology Of Groundwater Polluted By Nitrate In Jiaozhou Qianhan

China is a state that deficient of water resource and the availability water is only2300cubic meters per capita per year, and what is a quarter of the world’s average. Especially inarid, semiarid and water shortage regions of western, groundwater is a more kind of preciousresource. Groundwater is a very important component of the world’s water resources system.With the high-speed development of national economy and the improvement of people’sliving standard, groundwater developing is not reasonably, supplying and demanding tensionmake groundwater becoming nervous intensifies. Especially, water pollution was more andmore pay attention by people. Nitrate is a wide range of distribution and growing pollutant. In2005, monitored data about126underground water wells in Jiaozhou showed that the mainpollutant of groundwater was nitrate nitrogen and the maximum assessment was85.2mg/L.Agricultural activity was regarded as the main source of nitrate in groundwater. Nitrate is notonly caused human living environment pollution, but also harmed to human health. Theoriginal repair polluted groundwater method was pump-treat technology. The cost of this kindmethod was high and the effect of governance was often not ideal. Permeable ReactiveBarrier （PRB） technology is a high efficiency and feasible technology in situ repair ofpolluted groundwater and this is proved. With zero-valent iron （Fe⁰） as reaction media, Fe⁰-PRB technology is an important branch of PRB technology, which acquire materials easily,price is cheap, simple operation, high efficiency and sustainability strong advantages such aswide attention and get fast advance, so it has become research hot spot at domestic andforeign in recently20years.This study through batch test and column test, used groundwater polluted by nitrate inQianhan JiaoZhou as research object, and researched the main influence factors and removeeffect about iron powder as the main PRB reaction media to remove nitrate. This paperdiscussed Fe⁰-PRB as a better medium composition and better feasibility to the nitratepollution of Qianhan JiaoZhou groundwater, get the following conclusions:（1） Batch test results showed that the best effect of nitrate removed by iron is in acidicenvironment. In addition, small particle size, more impurity content, iron powder surfacepretreatment, improve oscillation speed, increase iron powder consumption, reduce solution concentration and join activated carbon can increase nitrate nitrogen removal amount atdifferent degree. Including iron powder surface pretreatment played a greater role. So Ichoose water washed rusty industry iron powder as the main reaction medium.（2） Batch test results also showed that the addition of cationic Fe²⁺, Fe³⁺, Cu²⁺and Zn²⁺can promote the nitrate reduction. Promoting effect order from high to low is: Zn²⁺> Cu²⁺>Fe³⁺> Fe²⁺. In the reaction system, Fe²⁺played a very important role for the nitrate reduction.It not only sped up the electronic transfer, but also involved in the reduction reactions andtranslated into Fe3O4. The influence of joined anions C2O4^2-, HCO^3-, CO3^2-, CH3COO-andHPO4^2-is not work to nitrate reduction. Among of them, C2O4^2-can promote nitrate reduction.The main effect is through the complex or chela cooperation to speed up the dissolution of theiron and reduce iron oxide and the formation of hydrogen chloride in a certain extent.However, HCO^3-, CO3^2-, CH3COO-and HPO4^2-can inhibit of nitrate’s reduction, the order ofinhibition was CH3COO-> HPO4^2-> HCO^3-> CO3^2-.（3） The results of column test study showed that the addition of sand particle size andquantity can affect the nitrate remove. So this paper used coarse sand as dispersion quality, theratio of iron powder and coarse sand is4:6. Join the activated carbon and sawdust canpromote nitrate removal. The major product of iron powder reduction of nitrate nitrogen wasammonia nitrogen. And at the same time, it caused pH value increased. Join the sawdustwhich produced nitrite nitrogen. Activated carbon can not only increase the reaction mediapermeability coefficient, but also can improve water quality. The finally, the determination ofPRB reaction media was washing rust industrial iron powder, activated carbon, coarse sandand their volume proportion is3:1:6.（4） In order to get the PRB to achieve the desired purposes, I need to take into account ofmany influencing factors. The main difficulty which I faced in the study was jam. Therefore,in filed reactor design, solution initial concentration, flow velocity and correspondingparameter should be consistent, the permeability coefficient is1.5-2.5times of permeabilitycoefficient of field.