Isolation And Denitrification Efficacy Of A New Nitrate-Dependent Fe(?) Oxidation Bacterium

Nitrate is one of the common pollutants in water,which seriously damages the surface water and groundwater environment.And it causes great harm to human.How to remove nitrate pollution in water is a research hotspot in recent years.Microbial denitrification is one of the effective methods commonly used for reducing nitrate.Conventional heterotrophic denitrification requires the addition of a large number of organic carbon sources,which increases the operating cost and easily causes secondary pollution.Nitrate-dependent Fe(II) oxidation(NDFO)microorganisms can reduce the addition of organic carbon sources,which has a broad application prospect.This paper explored the denitrification characteristics of NDFO sludge,and obtained a high-efficient denitrification NDFO bacterium.The growth characteristics and denitrification efficiency of NDFO bacterium was studied.This study provided theoretical guidance for the practical application of the strainThis study domesticated NDFO sludge under two electron donor conditions and investigated the denitrification efficiency of the sludge.The results showed that the nitrate reduction capacity of NDFO sludge under the condition of composite electron donor was higher than that under the condition of single electron donor,and the NH4+-N concentration was lower.As the increase of Fe(?)concentration,sludge reduction rate of NO3--N was in downward trend after rising first.When Fe(?)concentrations was 40 mg·L-1,denitrification rate reached the highest.In the range of NO3--N concentration less than 80 mg·L-1,the reduction rate of NO3--N increased with the increase of NO3--N concentration.A high-efficiency NDFO strain Fe-7 was isolated from the domesticated stable NDFO sludge.Fe-7 was a flagellated rod-shaped bacterium.The reduction rate of 50 mg·L-1 NO3--N by strain Fe-7 was 95.49%,and there was no accumulation of NO2--N and NH4+-N in the denitrification process.When NO3--N was 50 mg·L-1,the maximum reduction rate of NO3--N by strain Fe-7 was 1.17 mg·L-1·h-1.The growth curve of the strain was drawn and its growth characteristics were mastered.The optimal denitrification conditions of strain Fe-7 were investigated.With sodium potassium tartrate as the carbon source,NO3--N had the best reduction effect.The reduction rate of 55 mg·L-1 NO3--N was 89.85% after denitrification.When COD/N was 3,Fe-7 can perform complete denitrification,thus saving the use of carbon sources.The neutral condition is more suitable for the growth of Fe-7.The ability of the strain to grow and metabolize under acidic conditions is very low.The denitrification effect under alkaline condition is lower than that under neutral condition.When Fe(II)was within 10 mg·L-1,Fe(II)promotes denitrification.The promoting effect increased with the increase of Fe(II)concentration.However,when Fe(II)was higher than 10 mg·L-1,Fe(II)showed inhibitory effect.The higher the Fe(II)concentration was,the more obvious the inhibition was.