Study On Nitrate Removal From Groundwater And Biological Diversity With A Strengthening Biofilm Electrode Reactor

Nitrate contamination of groundwater has become a widespread concern environmental problem. Nitrate concentration in groundwater aquifers has steadily been increasing over the years mainly due to the extensive use of chemical fertilizers in intensive agriculture as well as discharge of domestic and industrial wastes. High levels of nitrate in drinking water will pose a serious threat to human health.Biological method is the most cost-effective approach. However, the traditional method of biological denitrification still has many disadvantages. In this study, a strengthening biofilm- electrode reactor has been designed for overcome the disadvantages of biological methods. The nitrate remove from groundwater by this reactor has been studied. Biological diversity of the reactor has been monitored by use of molecular biology methods.This study is to investigate the performance of the strengthening biofilm- electrode reactor affect by electrochemical reduction,C/N,phosphate and current intensity. The result show that: the nitrate remove by electrochemical reduction is very weak and the main role of electrode is the hydrogen producing by hydrolysis; Carbon source is a critical parameter. In this study, the optimum C/N is 1.00. Nitrate nitrogen removal rate reached 96%, nitrite concentration 0.02 mg/L and no methanol as carbon source found in effluent. Lack of phosphate, nitrate nitrogen removal rate slight decrease when C/N =1.25 and 1.00.The rate is 84.6% and 82.6%, respectively. At low C/N conditions, nitrate nitrogen removal rate remarkable decrease, is only 47.6%. At the same time, the accumulation of nitrite has a significant increase. Nitrite nitrogen in effluent up to 10mg/L caused a serious impact on water quality. Current intensity increase has an accelerating influence for the efficiency of strengthening biofilm- electrode reactor. However, current intensity increase exist an optimum value. Exceed this value, current intensity increase plays an inhibition role. In this study, the optimum value is 40mA.The evolution of reactor system was studied with denaturing gradient gel electrophoresis(DGGE). The results indicated Acetobacterium andγ- proteobacterium were dominant at the beginning, then progressively replaced byβ- proteobacterium. Hydrogenophaga sp,Pseudomonas sp,Alcaligenes sp,Denitratisoma sp were dominant at current has passed.In a word,β-proteobacteria is dominant in reactor.