Isolation, Identification And Nitrogen Removal Characteristics Of A Marine Heterotrophic Nitrification-aerobic Denitrification Bacterium And Its Application

Eutrophication problems in waterbodies, which were caused by nitrogen pollution, becomemore and more serious. Bio-treatment technology is widely used in removal nitrogen fromwastewater because of its high efficiency and low cost. However, several industries such as foodprocessing, fish processing, petroleum production, and the use of sea water as a substitute forfresh water in municipal sanitation, generate highly saline wastewater. High salinity can inhibitgrowth and activity of common microorganism, leading to poor efficiency of nitrogen removal.In this paper, a novel halophilic heterotrophic nitrification-aerobic denitrification bacteriumSF16was isolated from ocean sediments in Xiamen city, and was identified as Vibriodiabolicus，named as SF16by its morphologic observation, physiological characteristics analysisand16S rDNA gene sequence analysis.Heterotrophic nitrification characteristics of strain SF16were studied, which demonstratedthat after48h-cultivation in salinity of3.0%, the concentration of NH4+–N was reduced from119.77mg/L to10.96mg/L with a removal of90.86%NH4+–N, and the levels of NO2––N andNO3––N accumulation were all very low during the nitrification. The optimal conditions for theNH4+–N removal and growth of strain SF16were the presence of salt concentration of1~5%,initial pH range of7.5to9.5, C/N ratio of10, shaking speed of about140rpm, and the suitablecarbon sources were sodium acetate, sodium succinate, glucose and saccharose.Aerobic denitrification characteristics of strain SF16were investigated. Strain SF16showedefficient aerobic denitrifying ability. The aerobic denitrification of the strain occurred mainly inits logarithmic growth phase. After48-cultivation, the concentration of NO3––N was reducedfrom136.43mg/L to0.39mg/L with a removal of99.71%NO3––N. Moreover, there was only asmall amount of NO2––N accumulation, and the removal rate of TN reached98.28%. Theperiplasmic nitrate reductase (napA) gene was amplified successfully, which further proved theaerobic denitrification ability of strain SF16. The key factors affecting denitrification of strainSF16were surveyed. NH4+–N removal could reach above95%at salinity of3.0~5.0%. However,it did not grow in the absence of NaCl, which indicated that strain SF16strictly require NaCl forthe growth. Sodium acetate, glucose, sodium succinate and sucrose were favorable carbonsources.The optimum conditions for aerobic denitrification were salinty of3~5%, C/N ratio of10, initial pH range of7.5to9.5, temperature of30℃and shaking speed of120~140rpm. The effects of metal ions (Mg2+, Cu2+, Mn2+, Fe2+, Zn2+) on nitrogen removal of strain SF16were investigated. The results indicated that the capacity of nitrogen removal was promoted byMg2+and Mn2+while inhibited by Cu2+. It was found to have promoting effect on nitrogenremoval based on tests when Fe2+was less than10mg/L. However when Fe2+was more than10mg/L, the inhibitory effect on nitrogen removal may be produced. Zn2+showed neither inhibitorynor promoting effect on nitrogen removal when range of0~5mg/LThe halophilic heterotrophic nitrification-aerobic denitrifying bacterium was applied in thebiological aerated filter with oyster shell as the filler to treat saline wastewater. The resultsdemonstrated the removal efficiencies of NH4+–N, TN and COD by the biological aerated filter(BAF) reached97.14%,73.92%and55.20%, respectively. The concentration of NH4+–N, TN ineffluent reached the standard for water pollutants from municipal wastewater treatment plant(GB18918-2002). These results indicated that SF16have great potential for future full-scaleapplications.