Three Isolation, Identification And Degradation Characteristics Of Mild Halophilic Denitrifying Bacteria

In recent years,due to the rapid development of industry and agriculture,the content of nitrate in the wastewater discharged into the water is becoming higher and higher and have caused serious eutrophication,the quality of water depravation and the lake degenerate.Sometimes,the contaminated water will threaten the people health as the water source.The biological nitrogen removal process has many advantages such as cheap in cost, easy in operation,convenient in treatment so it has been widely used in wastewater treatment.In petroleum,chemical,seafood process industry,most of the discharge is hypersaline wastewater.In high-salt environment,the salting-out effect may decrease the microorganisms' dehydrogenase activity,lead to microbial cells rupture.Sometimes,the salting-out effect even cause death of microbial.So the high salt concentration has a negative impact on the biological nitrogen removal effect.Therefore,the isolation of denitrifying bacteria from hyperhaline habitats will provide a reference value for hyperhaline biological nitrogen removal process.In this paper,we have accomplished the enrichment,islation and screening experiments from the salt-tolerant sludge systems using nitrate as the sole nitrogen source. Six strains of halotolerant denitrifying bacteria were preliminary islated from the activated sludge.According to the degradation characteristics of various strains,we selected three of them for the following tests.According to the morphological observation,physiological biochemical test and sequence analysis of the 16S rDNA,strain FX1 was identified as Pseudomonas sp.;strain YL-1 was identified as Dietzia sp.;strain GYL was identified as Halomonas sp..We have investigated seven different effect factors effecting the degradation characteristics such as salinity,DO,inoculum concentration and so on to get the optimal degradation condition of each strain.The heterotrophic nitrification perfermance of the three bacteria has been found. When these three bacteria were cultured in the DM medium,they have higher nitrogen removal efficiency.And the relationship of aerobic denitrification and heterotrophic nitrification perfermance about FX1 was discussed.The result showed that aerobic denitrification can promote the effect ofheterotrophic nitrification. These three bacteria are aerobic denitrifying bacteria which can simultaneously perform heterotrophic nitrification,so they can realize simultaneous nitrification and denitrification(SND).The three bacteria can achieve SND in hyperhaline environment,so our tests have big application value for nitrogen removal of hyperhaline wastewater.