Comparison of aerobic denitrification under high oxygen atmosphere by Thiosphaera pantotropha ATCC 35512 and Pseudomonas stutzeri SU2 newly isolated from the activated sludge of a piggery wastewater treatment system

Aims: This study compares the ability of Thiosphaera pantotropha ATCC 35512 and the newly isolated Pseudomonas stutzeri SU2 to perform aerobic denitri fication. Methods and Results: Nitrate-supplemented basal medium in airtight crimp-se aled serum bottles containing an atmosphere of 92% oxygen was inoculated wi th Ps. stutzeri SU2 or T. pantotropha and incubated at 30 degreesC. During the 92-h incubation period, aerobic denitrification by Ps. stutzeri SU2 (NO 3- - N removal 99.24%) was more efficient than that by T. pantotropha (NO3- - N removal 27.29%). Conclusions: Pseudomonas stutzeri SU2, which was isolated from the activate d sludge of a sequencing batch reactor treating piggery wastewater, rapidly reduced the nitrate to nitrogen gas without nitrite accumulation. The nitr ate removal rate of SU2 was 0.032 mmol NO3- - N g cell(-1) h(-1) after 44 h incubation. Significance and Impact of the Study: Pseudomonas stutzeri SU2 can be used in a full-scale sequencing batch system for efficient in situ aerobic nitra te removal from piggery wastewater.