Nitrite Oxidation in Wastewater Treatment: Microbial Adaptation and Suppression Challenges

Microbial nitrite oxidation is the primary pathway thatgeneratesnitrate in wastewater treatment systems and can be performed by avariety of microbes: namely, nitrite-oxidizing bacteria (NOB). SinceNOB were first isolated 130 years ago, the understanding of the phylogeneticaland physiological diversities of NOB has been gradually deepened.In recent endeavors of advanced biological nitrogen removal, NOB havebeen more considered as a troublesome disruptor, and strategies onNOB suppression often fail in practice after long-term operationdue to the growth of specific NOB that are able to adapt to even harshconditions. In line with a review of the history of currently knownNOB genera, a phylogenetic tree is constructed to exhibit a wide rangeof NOB in different phyla. In addition, the growth behavior and metabolicperformance of different NOB strains are summarized. These specificfeatures of various NOB (e.g., high oxygen affinity of Nitrospira, tolerance to chemical inhibitors of Nitrobacter and Candidatus Nitrotoga, and preference to high temperature of Nitrolancea) highlight the differentiation of the NOB ecological niche in biologicalnitrogen processes and potentially support their adaptation to differentsuppression strategies (e.g., low dissolved oxygen, chemical treatment,and high temperature). This review implicates the acquired physiologicalcharacteristics of NOB to their emergence from a genomic and ecologicalperspective and emphasizes the importance of understanding physiologicalcharacterization and genomic information in future wastewater treatmentstudies.