Isolation And Identification Of Heterotrophic Nitrification Bacteria And Its Application In Refinery Wastewater Denitrification

Due to the excess of nitrogen emissions,water eutrophication become one of major problems of water environment in our country. A variety of methods are used for wastewater denitrification, wherein the biological denitrification is considered as one of most cost-effective methods. With wastewater discharge standards are getting higher and higher, traditional biological denitrification have been increasingly unable to meet the requirements, So in recent years the research and application of heterotrophic nitrifier and aerobic denitrifier being a hot spot, and it is expected to overcome the defects of the traditional nitrogen removal process and enrich the biological denitrification theory.Three strains of heterotrophic nitrifiers, named HN-1、HN-2and HN-3, is isolated from refinery wastewater treatment activated sludge.The sequence analysis and homology blast showed that the strains are the relative of A. Haemolytius Acinetobacter sp. and Acinetobacter sp. With100%、99%and98%sequence similarity respectively. Moreover, according to the phylogenic tree established by means of physiological and biochemical appraisals and16S rDNA sequencing, HN-1and A. Haemolytius BA56were in same branch、HN-2and Acinetobacter sp. JMC-UBL15were in same branch、HN-3and Acinetobacter sp. AUH-JLM455were in same branch.The optimal growth condition was as follows:inoculation amount5%, temperature30～35℃, initial pH8.0～8.5.The nitrification performance of the different strains were measured, the results show that all three strains have heterotrophic nitrification and aerobic denitrification abilities.In the artificial wastewater with105.83mg/L ammonia nitrogen as initial concentration,the removal efficiency by strains were96.54%、98.40%and96.85%respectively after20h cultivation.The average nitrogen removal rate were6.22mg-N/L/h、8.27mg-N/L/h and7.06mg-N/L/h respectively in exponential phase.The effects of m(C)/m(N), temperature, pH, shaking speed and concentration of NH4+-N on denitrification of three strains were investigated.The results show that the optimal conditions for NH4+-N removing are as follows:temperature30℃, pH8.5, shaking speed200r/min, m(C)/m(N)=12, initial NH4+-N100mg/L.The contrast on their growth characteristics and culture conditions shows that strain HN-2has a better adaptability, it can achieve NH4+-N removing rate of94.93%from refinery wastewater after24h. Compared with common activated sludge process, the nitrogen removal efficience of HN-2enhanced activated sludge system increased about10%.Later,more experiments are done to see the effect of nitrogen removal using active sludge technics strengthen by heterotrophic nitrification bacteria.The result shows that this method can improve the efficiency of nitrogen, COD removal of refinery wastewater.The effluent ammonia concentration is less than5mg/L.NH4+-N, COD removal efficiency are closed to99%, and the total N removal are over80%.