Reactive and microbial inhibitory mechanisms depicting the panoramic view of pH stress effect on common biological nitrification. (1st March 2023)

• Record Type: Journal Article
• Authors: Yue, Xuehai; Liu, Hong; Wei, Haotian; Chang, Lin; Gong, Zhengjun; Zheng, Lei; Yin, Fengjun
• Is Part Of: Water research. Volume 231(2023)
• Publication Date: 2023-03-01
• Subjects: Nitrification -- pH stress effect -- Reactive inhibition -- Microbial inhibition -- Free ammonia; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2023.119660
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Proposing comprehensive experiments investigating pH stress effect on nitrification. Disclosing reactive inhibitory mechanism dominating in acid range. Revealing hybrid pH stress effect with free ammonia. Gaining a panoramic view understanding pH stress effect on nitrification. Abstract: pH is a crucial factor of microbial nitrification, which often combines with high-strength ammonium to influence nitrogen removal pathway in wastewater treatment. However, the detailed inhibitory mechanisms of pH stress are not sufficiently disclosed yet. In this study, the pH stress effect on nitrification was comprehensively studied by a set of experiments which identified the reactivity of nitrification processes and activity of nitrifiers, the time dependence of inhibition effect and the hybrid pH stress effect with ammonium. The results revealed two distinct inhibitory mechanisms dominating in alkaline and acid ranges. In alkaline range (pH > 8), pH stress causes physiological damages on microorganisms which is named as microbial inhibition. It has the features of less recoverability of nitrifiers, time-dependent inhibition effect and low pH-tolerance of nitrite oxidation bacteria. Free ammonia enhanced microbial inhibition and greatly promoted nitrite accumulation. A novel reactive inhibition mechanism dominated in acid range (pH < 7) was disclosed. It only impedes ammonia oxidation process (AOP) but not impair microbial activity obviously and the effect is time-independent. The mechanism was clarified from H + transport because AOP involved H + production. The H + transport was impeded under acid stress owing to the decrease of pH gradient across cell membrane. The two mechanisms formed a panoramic view of pH stress effect on nitrification advancing the understanding of nitrifier adaptability and nitritation regulation in wastewater treatment processes. Graphical abstract: Image, graphical abstract