Abstract
The sensitivity of anaerobic ammonium-oxidizing (anammox) bacteria to environmental fluctuations is a frequent cause of reactor malfunctions. It was hypothesized that the addition of formate and folate would have a stimulating effect on anammox bacteria, which in turn would lead to the stability of the anammox process under conditions of a sharp increase in ammonium load, i.e., it helps overcome a stress factor. The effect of formate and folate was investigated using a setup consisting of three parallel sequencing batch reactors equipped with a carrier. Two runs of the reactors were performed. The composition of the microbial community was studied by the 16S rRNA gene profiling and metagenomic analysis. Among anammox bacteria, Ca. “Brocadia” spp. dominated during the first run. A stimulatory effect of folate on the daily nitrogen removal rate (dN) was identified. The addition of formate led to progress in dissimilatory nitrate reduction and stimulated the growth of Ca. “Jettenia” spp. The spatial separation of two anammox species was observed in the formate reactor: Ca. “Brocadia” occupied the carrier and Ca. “Jettenia”—the walls of the reactors. Biomass storage at low temperature without feeding led to an interspecies shift in anammox bacteria in favor of Ca. “Jettenia.” During the second run, a domination of Ca. “Jettenia” spp. was recorded along with a stimulating effect of formate, and there was no effect of folate on dN. A comparative genome analysis revealed the patterns suggesting different strategies used by Ca. “Brocadia” and Ca. “Jettenia” spp. to cope with environmental changes.
Highlights
Anaerobic ammonium-oxidizing bacteria carry out anoxic oxidation of ammonium with nitrite to dinitrogen gas coupled with the production of small amounts of nitrate (Strous et al, 1998)
Since the daily nitrogen removal rate (dN) did not decrease in this period, and the amount of ammonium in the effluent did not increase, it can be assumed that total nitrogen removal occurred in the future control reactor due to the process of nitri-denitrification, rather than nitritation-anammox
It was suggested that the addition of formate and folate would have a stimulatory effect on anammox bacteria, which in turn would lead to the stability of the anammox process under conditions of increased ammonium loads, i.e., it would help overcome a stress factor
Summary
Anaerobic ammonium-oxidizing (anammox) bacteria carry out anoxic oxidation of ammonium with nitrite to dinitrogen gas coupled with the production of small amounts of nitrate (Strous et al, 1998). The. Interspecies Shift of Anammox Bacteria sensitivity of anammox bacteria to changes in temperature; pH; and concentrations of dissolved oxygen (DO), ammonium, nitrites, sulfides, and organic compounds is a frequent cause of reactor failures in actual conditions of wastewater treatment facilities (Lackner et al, 2014; Cho et al, 2020). Interspecies Shift of Anammox Bacteria sensitivity of anammox bacteria to changes in temperature; pH; and concentrations of dissolved oxygen (DO), ammonium, nitrites, sulfides, and organic compounds is a frequent cause of reactor failures in actual conditions of wastewater treatment facilities (Lackner et al, 2014; Cho et al, 2020) In this respect, it is essential to look for metabolic effectors (regulators) that would allow the anammox community to cope with unfavorable fluctuations in external conditions and help maintain the stability of nitrogen removal from wastewater. Anammox bacteria were shown to express the narG gene for the reduction of nitrate to nitrite in Fe0/Fe2+-dependent partial DNRA, whereas ammonium was produced from nitrite by abiotic reduction, facilitated by Fe0 and Fe2+ (Bi et al, 2020)
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