Growth of Nitrosococcus-Related Ammonia Oxidizing Bacteria Coincides with Extremely Low pH Values in Wastewater with High Ammonia Content

Abstract

Ammonia oxidation decreases the pH in wastewaters where alkalinity is limited relative to total ammonia. The activity of ammonia oxidizing bacteria (AOB), however, typically decreases with pH and often ceases completely in slightly acidic wastewaters. Nevertheless, nitrification at low pH has been reported in reactors treating human urine, but it has been unclear which organisms are involved. In this study, we followed the population dynamics of ammonia oxidizing organisms and reactor performance in synthetic fully hydrolyzed urine as the pH decreased over time in response to a decrease in the loading rate. Populations of the β-proteobacterial Nitrosomonas europaea lineage were abundant at the initial pH close to 6, but the growth of a possibly novel Nitrosococcus-related AOB genus decreased the pH to the new level of 2.2, challenging the perception that nitrification is inhibited entirely at low pH values, or governed exclusively by β-proteobacterial AOB or archaea. With the pH shift, nitrite oxidizing bacteria were not further detected, but nitrous acid (HNO2) was still removed through chemical decomposition to nitric oxide (NO) and nitrate. The growth of acid-tolerant γ-proteobacterial AOB should be prevented, by keeping the pH above 5.4, which is a typical pH limit for the N. europaea lineage. Otherwise, the microbial community responsible for high-rate nitrification can be lost, and strong emissions of hazardous volatile nitrogen compounds such as NO are likely.

Effects of the Use of Ornamental Plants and Different Substrates in the Removal of Wastewater Pollutants through Microcosms of Constructed Wetlands

“…In Figure 5A, the pH values obtained in both influent and effluent are shown. They ranged between 6.8 and 7.6 in RVG and between 6.6 and 7.8 in PET, being within typical values of domestic wastewater [49]. The decreases in the pH of some of the data ( Figure 5B) are based on the removal of nitrogen that occurs in these systems, which causes a reduction in alkalinity [50].…”

Ammonia oxidation at pH 2.5 by a new gammaproteobacterial ammonia-oxidizing bacterium

“…16S rRNA gene sequence-based phylogenetic analysis including searching the IMNGS platform ( https://www.imngs.org/ ) (Supplementary Fig. 2A ) revealed that the most closely related sequences were obtained from a refuse dump of leaf-cutter ants [ 36 ] (>99% identity), from a Finnish soil (PRJNA393827), and from a synthetic urine nitrification reactor [ 37 ], the closest cultured species was “ Ca . Ng.…”

“…terrae” [ 11 ] exhibited activity at pH of 4 and 5, respectively. In addition, Nitrosococcus -like species were found to be dominant in reactors treating human urine down to pH 2.2 [ 37 ]. The ability of oxidizing ammonia at low pH could be due to different adaptation mechanisms, metabolic flexibility, or by the cooperation between different species in the environment [ 5 , 13 , 20 ].…”

“…RJ19 does not seem to be distributed in marine environments. Metagenomic sequence data (IMNGS platform) showed that closely related sequences (based on 16S rRNA gene similarity) were found in a refuse dump of leaf-cutter ants [ 36 ], in a soil in Finland and in a synthetic urine nitrification reactor [ 37 ], which all are environments with significant nitrogen cycling and high ammonium concentrations. Furthermore, similar 16S rRNA gene sequences were retrieved from sewage and bat guano (Supplementary Fig.…”

Comparison of different cultures and culturing conditions for the biological deterioration of organic load from real saline bilge wastewater: microbial diversity insights and ecotoxicity assessment

“…In all mixed anaerobic cultures (MAnC 1, MAnC 2 and initial granular sludge used as inocula), some of the most abundant bacteria groups (class and genus) were Gammaproteobacteria (Nitrosococcus), Thermotogae ( M e s o t o g a ) , A c t i n o b a c t e r i a ( B r o o k l a w n i a ) , Deltaproteobacteria (Syntrophorhabdus) and Nitrospira and Anaerolineae uncultured genus. Nitrosococcus genus are Ammonia Oxidizing Bacteria (AOB), adapted to saline and acidic environments, regularly found in marine environments but less commonly detected in waste water treatment reactors (Fumasoli et al 2017). Mesotoga are frequently found in oil-polluted marine mesophilic anaerobic environments (Nesbø et al 2019).…”