Research On Technology Of Partition PRB In-situ Remediation Of Groundwater Nitrogen Pollution

Groundwater, which is an important component of water resources, is one of the mostvaluable freshwater resources. Because of the rapid development of economic andsociety, expanding of the scale of agriculture and industry and the soar of pollutantemission, the groundwater contamination by inorganic nitrogen (in the form of NO3-,NO2-, NH4+) pollution became worse and worse. Long-term drinking of nitrogen pollutedgroundwater may cause methemoglobinemia, liver damage, cancer as well as otherdiseases, especially cause more serious disease to children. Thus, groundwatercontamination by inorganic nitrogen constitutes a major environmental concernworldwide.This study was supported by the national "five" National Science and TechnologySupport Program "Northeast alpine area towns drinking water security technologyintegration and demonstration"(2012BAJ25B10). We present a new three-layerpermeable reactive barrier (PRB), which is more economic and efficient to fit the qualityof inorganic nitrogen polluted groundwater and the component characteristics.In this research, suitable natural substrate and artificial media as potential carbon sourceand oxygen release material for use in a nitrification, denitrification and control ofsecond pollution prevention permeable reactive barrier (PRB). According to thesimulation study of the three-layer PRB demonstration, the program progress of PRBwas decided and the PRB demonstration will offer technical assistance for industrialapplications.First of all, suitable natural organic substrates(paper, wood chips and walnut shells),natural semi-inert solid-phase organic carbon (12samples of lignite from Sanjitun,Akesu, Faku, Zhangdang, Pingzhuang, Zhangjiakou, Wangniutan, Longkou, Lingshi,Yima, Ruzhou and Zhaotong) and man-made solid carbon metieral (HE made of40%hemp fiber and60%polyethylene; HB made of40%hemp fiber and60%poly(butylenesuccinate), HL made of40%hemp fiber and60%polylactic acid) were selected andinvestigated. At the condition of the influence nitrate concentration of30mg/L,19±1℃and hydraulic retention time of24h, the nitrate removal rate of the column with walnutshells as carbon source was95%. Meanwhile, during the180days of running, the carbonrelease of walnut shells didn’t decrease, and the acute toxicity of effluent was safe.Secondly, the oxygen release material made with clay and CaCO3was tested under thecondition of water flow rate of0.02m/s. It was found that the DO of effluent can bestable around7mg/L for169days, which means the material performed a long-term oxygen releasing capacity.According to the media selection study, walnut shells and oxygen release material madeof clay and CaCO3were used as the main active media in the simulative three-layer PRB.The simulative groundwater, which is similar to the characteristics of the demonstrationproject site groundwater components and condition, contained ammonia of2mg/L andnitrate of30mg/L at15℃, with the water flow rate of0.02m/d. The effluent was foundto reach the "drinking water health standards"(GB5749-2006) and the class Ⅲ of"groundwater quality standards (GB/T14848-93)". Finally, it was successfully utilized inthe demonstration project.Application of this technology performed a very important role in the protection of urbanand rural residents living water, supporting the development of society and economic, aswell as maintain ecological balance. Meanwhile, the three-layer PRB situ remediationtechnology does not utilize extra land, which makes it efficient, economical andenvironmentally friendly.