Characteristics of an aerobic denitrifier isolated from unconfined aquifer

Abstract

An aerobic denitrifier strain named X11 was isolated from the shallow unconfined aquifer samples in Suzhou city, China. According to the physiological biochemical identification and the 16S rDNA gene analysis, the strain X11 was generally identified as Pseudomonadales Pseudomonadaceae. Single factor experiments were used to investigate the influence of temperature, pH and carbon sources on its growth and denitrification characteristics. The results showed that under aerobic conditions the total nitrogen loss and nitrate reduction efficiency within 60 hours were up to 70.3% and 95.1%, respectively, with initial nitrate concentration of 276.25 mg/L. The nitrate removal rates reached 18.24 mg/L·h within 12 hours. It was found that strain X11 can convert nitrate into nitrogen gas without obvious accumulation of nitrite under aerobic conditions. The pH increased and ORP decreased by activated denitrifier in liquid medium. the optimum conditions were obtained as follows; temperature value of 30° C, pH value of 7. The results indicate that the isolated aerobic denitrifier XK11 has high nitrogen removal efficiency, it may be a good candidate for in-situ bioremediation of nitrogen-contaminated shallow groundwater or aerobic wastewater treatment.