Study On Remediation Of Nitrate Pollution In Groundwater Through PRB Combined With Plant

China’s water shortage is extremely serious and groundwater is one of the most important fresh water resources.In our country,there are more than 7 million people drinking water.With the rapid development of industry and the rapid increase of human activities,more than 50% of the ground water is polluted by nitrate.Domestic sewage discharge,chemical fertilizer,organic manure application and industrial pollution have led to a sharp increase in the discharge of nitrate.Biodegradation PRB has the characteristics of high economic efficiency and is one of the best repair technology.However,Biodegradation PRB has the problems of easy blocking of medium and large fluctuation of water quality.This limits Biodegradation PRB widespread use.Based on this,the article first introduce the influence of PRB on the stability of groundwater and the biological denitrify effects taking the mixture of straw compost humus soil and fine sand as the medium.And then in the case of the best medium ratio,the article introduce the plant combined with biodegradation PRB and biodegradation PRB on nitrate removal in groundwater studying the effects of different plants combined with biodegradation PRB on nitrate removal in groundwater.According to the law of the change of nitrate and ammonia nitrogen in PRB,this paper is to find the reason of the effect of PRB and the method of improving the ability of PRB repair.Finally,this paper examines the effects of PRB operating parameters(influent concentration,thickness of the reaction medium,DO)on the nitrate removal in the groundwater of the plant combined with biodegradation PRB.The main results obtained in this paper are as follows:1.Remediation of contaminated groundwater with straw compost humus soil as PRB medium is feasible.The straw compost humus will release the nitrate and ammonia which caused secondary pollution of groundwater.The ratio of 1:50 plant straw compost humus and sand mixture for PRB medium repair nitrate effect is the best.The nitrate removal rate can reach 93%,which is in accordance with the standards of groundwater quality.But the PRB still has the problem of deposition of nitrate deposition at the bottom of the device and high ammonia nitrogen concentration.2.The plant root through the "pump" effect can effectively solve the prroblems that nitrate deposition and the effluent ammonia concentration is higher.The plant can improve the efficiency and stability of PRB.But different plant root is different.Root length and development level and different ability to absorb nitrate make A lot of difference to enhance the effect of PRB.Corn have a better ability to improve the repair ability of PRB than typha.3.Influent concentration fluctuation can affect the effect of PRB on nitrate removal.And plants can reduce the influence of PRB on nitrate fluctuation of groundwater.4.The mixed medium straw compost humus soil and fine sand will release the nitrate and ammonia,so the medium thickness should not be too large.5.The effect of DO in water on the removal of nitrate by PRB is small,but it has a great influence on ammonia nitrogen.Therefore,in order to make the effluent ammonia nitrogen concentration to achieve a lower value,DO best to keep in the following 0.3mg/L.PRB combined with plant can remove nitrate from groundwater well and have the characteristics of stable operation,economic and environmental protection.So it has good application prospect and practical value.The research results of this paper have profound theoretical and practical significance to reduce the construction cost and the maintenance difficulty of the construction of the underground water in situ remediation of nitrate contaminated groundwater,to develop low energy consumption,low operation cost,no secondary pollution repair technology.