Three Halophilic Heterotrophic Nitrifying Bacteria Isolation And Identification Of Denitrification Characteristics

Nitrogen removal is essential for preventing eutrophication. In some industries, such as petroleum, fertilizer, and seafood process industry and so on, the wastewater contains high concentration of salt. High salinity can cause bacterial plasmolysis and loss of metabolic functions, so conventional biological nitrogen removal process is optimized only when operating under a low salinity environment. In addition, The traditional Bio-treatment method needs two processions, i.e. aerobic nitrification and anoxic denitrification, which makes this method more complex and expense, therefore it has become an issue for research to screening of heterotrophic nitrification bacteria with the capacity of simultaneous nitrification/denitrification.Using ammonium chloride as the sole nitrogen source, three strains of halophilic heterotrophic nitrobacteria gs1, gs2 and gs3 were separated from the matured activated sludge. According to the morphological observation, physiological biochemical tests and sequence analysis of the 16S rDNA, strain gsl was identified to be as Pseudomonas sp. Strain gs2 and gs3 were identified to be as Halomonas sp.Varying carbon sources, salinity, temperature, pH and C/N were investigated to identify the optimal conditions for nitrogen removal. The results were as follows:when sodium acetate was used as carbon sources, salinity 2%, temperature 30℃, pH 8.0, and C/N 7, the removal rates of the NH4+-N by the three strains were all over 80%. The results of salinity tolerance were as follows:the optimal salinity range of strain gsl was 0-5%; strain gs2 and gs3 both were 2-10%. So the three strains can tolerant a high ranges of salinity, which have great application value for nitrogen removal of hyperhaline wastewater.The aerobic denitrification of three strains were also studied in this paper, the results indicated that they can use nitrite and nitrate in the aerobic condition.Little nitrate or nitrite was detected during the removing of ammonia, and ammonia can be removed through transforming to gases. So these three bacteria not only had the capability of heterotrophic nitrification but also aerobic denitrification, and could complete the full process of biological deoxidation.The three bacteria can achieve SND in hyperhaline environment, so they have a great application value for nitrogen removal of hyperhaline wastewater.