Study On The Remediation Of Nitrogen Contaminated Groundwater By The Biological Immobilization Permeable Reactive Barrier

In view of the serious problem of groundwater nitrogen pollution,PRB can be used as a permeable reaction barrier to treat groundwater nitrogen pollution,so as to get better treatment effect in the treatment of nitrogen-polluted groundwater.This paper studies and designs an in-situ anaerobic double-layer system consisting of oxygen capture layer,which has the effect of repairing groundwater polluted by nitrogen.The first layer contains oxygen-containing reagents(zero-valent iron,ZVI),sodium citrate and other inorganic salts,which are used to consume dissolved oxygen(DO)in groundwater in order to create anaerobic conditions for denitrification.Carbon and phosphorus nutrients are provided to immobilize the normal metabolism of denitrifying bacteria in the second layer,and granular activated carbon is used as microbial carrier in the second layer,which biodegrade can nitrate into the barrier system.The removal rate of immobilized bacteria is higher because of the high concentration of local bacteria.A large number of experiments have been carried out to determine the effect of DO on biodegradation,the effectiveness of ZVI in capturing oxygen and the characteristics of oxygen capture materials prepared to stimulate the growth of denitrifying bacteria.At DO=0.02 mg/L,the biodegradation efficiency of nitrogen is the highest,which is about 85.31% in the treatment experiment.After adding 500 mg/l ZVI powder,DO value decreased significantly(from 6 mg/L to 1.61 mg/L).Adding materials prepared in the reactor to denitrify bacteria,the growth effect was better than that of the control group adding mineral medium.The results showed that the prepared materials could provide anaerobic conditions for the metabolism of denitrifying bacteria and microorganisms.Then two stainless steel columns with continuous upward flow were used to carry out laboratory-scale tests to evaluate the feasibility of the system.The first column is filled with granular oxygen-containing materials prepared by ZVI,sodium citrate and other inorganic salts.The second column was filled with activated carbon to immobilize denitrifying microbial coalition.The simulated nitrogen contaminated groundwater with dissolved oxygen content of 6 mg/l was pumped into the system at 236.75 ml/d.The nitrogen samples of the second column were analyzed and the nitrogen samples were mainly degraded through the production of nitrogen.The results showed that the removal rate of nitrogen could exceed 94%,and the metabolic intermediate nitrite could be further degraded in the passive system.