Isolation of aerobic denitrifying bacteria Stutzerimonas stutzeri and its application in coking wastewater treatment

Improvements in denitrifying bacteria since 1970 have optimized the activity of autotrophic denitrification and heterotrophic nitrification. Synchronous autotrophic biofilms, denitrification, and nitrification have enhanced nitrogen removal from industrial wastewater, but so far, this process relies on variables such as dissolved oxygen, pH, and carbon sources. The aerobic denitrification capability of the coking wastewater-derived Stutzerimonas stutzeri KA1 is quantified in the present investigation to enhance nitrogen removal potential under various environmental conditions. The strain was studied for its ability to isolate nitrate using sodium acetate as the carbon source, and the effectiveness of the microorganism was tested at different dissolved oxygen, pH, and C/N levels. Findings indicate that strain KA1 achieved nearly 100% nitrate elimination within 40 h at pH 6-10 and an optimal C/N ratio of 8, demonstrating resilience under both aerobic and anaerobic conditions. Strain KA1 showed robust denitrification across a wide range of dissolved oxygen levels (0-100%), including stable nitrate reduction under aerobic bulk conditions. Bioaugmentation experiments conducted in a Sequential Batch Reactor (SBR) confirmed that strain KA1 significantly enhanced nitrogen removal, particularly under saline wastewater conditions, exceeding the control systems. In conjunction with nitrogen elimination, the strain also demonstrates robust Chemical Oxygen Demand (COD) reduction, efficiently degrading organic pollutants in coking wastewater. Compared to other studies, Stutzerimonas stutzeri KA1 demonstrated higher denitrification efficiency and greater resistance to environmental stress, making it a scalable, cost-effective solution for denitrifying industrial wastewater. The results offer valuable insights into optimizing wastewater treatment parameters and can advance microbial biotechnology to foster sustainable environmental practices.