Nitrogen removal characteristics of Pseudomonas oryzihabitans EN-F4 with/without the supplementation of hydroxylamine

Abstract:

[Objective] The microorganisms with the function of heterotrophic nitrification-aerobic denitrification (HN-AD) play a key role in the biological removal of nitrogen, while little is known about the HN-AD microorganisms capable of simultaneous removing multiple inorganic nitrogen sources, especially hydroxylamine, from wastewater. In this study, a HN-AD strain EN-F4 capable of simultaneous removing hydroxylamine and nitrite was isolated from a vegetable field. We explored its nitrogen removal characteristics and the effects of hydroxylamine on the nitrogen conversion process, aiming to lay a foundation for improving the efficiency of wastewater treatment. [Methods] The strain EN-F4 was identified based on morphological characteristics and 16S rRNA gene sequence. Batch experiments were carried out to determine the nitrogen conversion characteristics of the strain EN-F4. The nitrogen balance, enzyme activity, and specific enzyme inhibitor tests were conducted to decipher the HN-AD mechanism of the strain EN-F4. Finally, the effects of hydroxylamine addition on the conversion of different nitrogen sources were explored. [Results] The isolate EN-F4 was identified as Pseudomonas oryzihabitans. The strain cultured at 25℃ showed the ammonium, hydroxylamine, nitrite, and nitrate removal efficiencies of 99.27%, 99.13%, 87.01%, and 85.20% and the maximum nitrogen removal rates of 8.27, 1.85, 5.10, and 5.31 mg/(L·h), respectively. The addition of hydroxylamine did not inhibit the denitrifying ability of the strain EN-F4, while it promoted the removal of nitrite and total nitrogen by the strain, with the maximum removal rates reaching 7.80 and 7.51 mg/(L·h), respectively. The enzyme activity, nitrogen balance, and specific enzyme inhibitors confirmed the strong HN-AD capability of the strain. [Conclusion] Pseudomonas oryzihabitans EN-F4 could efficiently remove inorganic nitrogen sources from wastewater by HN-AD at 25℃, and hydroxylamine could significantly promote the removal of nitrite and total nitrogen.