Experimental Research Of Applying Permeable Reactive Barrier (PRB) For Polluted Watercourse Remediation

The "permeable reactive barrier"(PRB) technology,a popular method of in situ remediation of contaminated groundwater widely used recently in Europe and America,is a passive treatment technology that removes dissolved contaminants from polluted water.The approach,compared to the earlier method,is charactered with in situ remediation,good long-term performance,many remediable contaminants and low costs.With the development of research,some abroad researchers have carried out the technologies of remedy contaminated surface water with PRB,while there are few reports in our country.Associated with the national 863 project,Study on the technologies of influent river water environment of DianChi treating and their demonstration project (2005AA601010-03),taking the Daqing River which was contaminated influent river of Dianchi as study object,a small-scale experiment,the degradation processes along length of these pollutants,and the optimal reactive parameters and the effects of treating polluted river water on permeable reactive barrier are studied in this paper. The main results are showed as follows.1.The results of the one-factor experiments show that low pH,longer reaction time and higher pollutant concentrations in initial water are all favorable to the reduction of TN and NO₃^--N by per g iron chipping.The nitrate and total nitrogen reduction by per g iron chipping increases with addition of manganese dioxide.The total nitrogen reduction by per g scrap iron increases from 0.05 mg.g^-1 to 0.17 mg.g^-1, the amount of reduction is treble.At the same time,the creation of ammonia also decreases.However,there is no variable tendency in reduction of nitrate and total nitrogen with addition of bamboo charcoals.2.The results of the one-factor experiments show that low pH,longer reaction time,and higher pollutant concentrations in initial water are all favorable to the reduction of TP and COD by per g iron chipping. 3.Orthogonal experiments of NO₃^--N,TN and TP are conducted by changing pH value,reaction time,pollutant concentrations and dosage of iron chipping.The influence of the four factors from high to low are:dosage of iron chipping＞reaction time＞influent concentration＞pH value,for NO₃^--N reduction;reaction time＞influent concentration＞dosage of iron chipping＞pH value,for TN reduction;dosage of iron chipping＞pH value＞influent concentration＞reaction time,for TP reduction. The optimal reactive parameters obtained from the experiments include:pH 6,dosage of iron chipping 0.7g,reaction time 150min,influent concentration of TP 1mg.L^-1, and influent concentration of TN 30 mg.L^-1.4.On the six PRB systems which have different proportion of reactive media,the One-way ANOVA test shows that significant differences(at the 0.05 level) exist among the removal ratio of TN,NO₃^--N,and NH₄⁺-N.The proportions of reactive media of PRB systems of⑤andâ‘¥are the desirable for their highest removal ratios of COD_Cr,TN,NO₂^--N,NO₃^--N,NH₄⁺-N,and TP,which are 56.58%,85.83%,96.31%, 76.62%,22.15%,82.04%,and 54.12%,79.24%,96.31%,75.69%,23.46%,80.97%, respectively.5.Concentrations of some pollutants,such as COD_Cr,TN,NH₄⁺-N,and TP,in the degradation processes along the length of PRB systems can be simulated with exponential equations.6.The correlative test indicates that the correlation between concentrations of iron ions and concentrations of COD_Cr,TN,NO₂^--N,NO₃^--N,and TP in the effluents from PRB systems were significant at the 0.05 level.