Enhanced Biological PRB Technology Promotes Degradation Of NH₄⁺-N And COD In Groudwater

With the rapid population growth and changes in lifestyles,the amount of urban waste is growing rapidly,but initial unhygienic landfills had weak anti-seepage measures.Then long-term leakage would cause serious pollution to the surrounding groundwater.For the groundwater contaminated by landfill leachate,this study uses hematite combined with biological treatment to promote the degradation of ammonia nitrogen and COD in the groundwater.Hematite is widely distributed in nature and lowly-cost,which is proper to be used as the reaction filler of the permeable reaction barrier（PRB）.The improved widdel medium was used to enrich and domesticate the indigenous microorganisms from the submerged paddy soil,that is,mixed bacteria with Fe（III）reduction function.This paper studies the anaerobic biological processes with mixed soil bacteria and S.putrefaciens,using hematite（α-Fe2O3）as the electron acceptor,and explores the extent of Feammox reaction in the system.Based on the concept of"treating waste with waste",straw was pyrolyzed at high temperature to prepare biochar materials,which was added as an electronic shuttle medium to build a strengthening system.The effects of the electronic shuttle mechanism on the anaerobic biological process of hematite were studied and the degradation reaction mechanism also be explored.At last,this study construct column experiment with dynamic degradation of the real polluted groundwater to optimize the operating parameters of the reaction column.The main conclusions are as follows:Two different bacterial liquids(mixed bacteria and S.putrefaciens were used to degrade ammonia nitrogen through the anaerobic biological process,using hematite as the electron acceptor.The NH₄⁺-N removal and total nitrogen loss of the system of mixed bacteria were higher than those of the single S.putrefaciens system.When the mixed bacteria reaction system with hematite was strengthened by the biochar prepared at high temperature,it was found that the initial reduction rate and reduction degree of Fe（III）were significantly improved at a certain biochar concentration.Real groundwater static degradation experiments show that the addition of biochar promotes the degradation of NH₄⁺-N and COD in groundwater.The COD removal rate in 25 days is increased to 60.38%,which is 3 times that of the system without biochar,and the removal rate of NH₄⁺-N is also increased after 25 days reaction,which is 49%.Column experiments simulate dynamic degradation of groundwater and optimization of the parameters can provide a basis for actual groundwater remediation projects.