Research On In-situ Remediation Of Nitrate Pollution In Groundwater

Because of human’s infinite demand and deliberately destroy, the nitrate pollution in groundwater has become more and more serious. It has become an environmental problem in today’s society, and makes serious influence to human life.This paper analyzes the present situation and the harm of the nitrate pollution in groundwater.Meanwhile, present remediation methods, such as physical method, chemical method and biologic method were compared.The permeable reactive barrier is a comparatively promising technology on in-situ remediation in groundwater.Aiming at the removal of nitrate in groundwater, first take some static tests of reaction medium. The pine sawdust which with good performance can release adequate carbon and less nitrogen.Then chose the pine sawdust and zero valent iron as the reaction filler. Then study the influences, such as differences between zero valent iron and pretreatment one, the proportion of sawdust and zero valent iron and the p H, to the subsequent reaction column. The analytic results show that the pine sawdust can provide carbon resources to the denitrifying bacteria. The best conditions of PRB,includes:p H=7,the pretreatment zero valent iron,Fe:C is 3:2, then the total nitrogen removal percentage was 72.11%.At the same time, the p H value range just coincide the natural underground water p H value range(p H value for 6-9).Then add the mixture of sawdust and zero valent iron into the self-made reactor column, the eight tests under different water velocity and inflow concentration show that the denitrification effect decreases along with the increase of inlet velocity range from 1cm/h to 7cm/h, but the final total nitrogen removal percentage was 100% in a week, the reflection effect of this device under this condition was good. When the inlet velocity range from 1cm/h or 3cm/h, the denitrification effect has no obvious differences. The by-product ammonia was added along with the increased nitrate nitrogen concentrations and no nitrite when it increased from 60mg/L to 120mg/L.Contrast to different filling ways with inlet velocity as 3cm/h and influent concentration as 80mg/L, long-term operation show that the effluent quality was well under both filling ways, with the total nitrogen removal percentages of 100% and 93.84%, respectively. The concentration of by-product ammonia had reduce to about 2.88mg/L under the sublevel filling way, the concentration of the NH4+ accounted for about 7% of the NO3- concentration which has been removed. The experiment demonstrate that the reactor column in sublevel filling way can effectively prevent the pollution. The dominate of microbial community composition of the sawdust were Pseudomonas、Diaphorobacter、Caulobacter.The analytic results demonstrate that in-situ remediation of nitrate pollution in groundwater by this equipment is possible.As long as the appropriate of the reaction filler and reasonable design of the device,this technology will play an important role in the engineering practice of in-situ remediation of groundwater pollution.