Metagenomic evidence of a novel anammox community in a cold aquifer with high nitrogen pollution

The process of anaerobic ammonium oxidation by nitrite (anammox) is a globally essential part of N cycle. To date, 8 Candidatus genera and more than 22 species of anammox bacteria have been discovered in various anthropogenic and natural habitats, including nitrogen-polluted aquifers. In this work, anammox bacteria were detected for the first time in the groundwater ecosystem with high anthropogenic nitrogen pollution (up to 1760 mg NO3--N/L and 280 mg NH4+-N/L) and low year-round temperature (7-8 °C) in the zone of a uranium sludge repository. Further metagenomic analysis resulted in retrieval of metagenome-assembled genomes of 4 distinct anammox bacteria: a new genus named Ca. Frigussubterria, new species in Ca. Kuenenia, and two strains of a new species in Ca. Scalindua. Analysis of the genomes revealed essential genes involved in anammox metabolism. Both strains of Ca. Scalindua chemeplantae had a high copy number of genes encoding the cold shock proteins CspA/B, which can also function as an antifreeze protein (CspB). Ca. Kuenenia glazoviensis and Ca. Frigussubterria udmurtiae were abundant in less N-polluted site, while Ca. Scalindua chemeplantae inhabited both sites. Genes for urea utilization, reduction of insoluble Fe2O3 or MnO2, assimilatory sulfate reduction, reactive oxygen detoxification, nitrate reduction to ammonium, and putatively arsenate respiration were found. These findings enrich knowledge of the functional and phylogenetic diversity of anammox bacteria and improve understanding of the nitrogen cycle in polluted aquifers.

Methods Influence in Surface Area Result from Polyurethane Used as Support Media

We evaluated if different measurement methods influence the surface area results from a polyurethane sponge used as support media in biofilm reactors. The surface area values are normally used to characterize and present advantages from supported medias. However, the methodology to determine it is barely discussed. We compared two specific surface area methodologies: Brunauer-Emmett-Teller (BET) and analysis of images obtained by a scanning electron microscope (SEM). Specific surface area by BET was 93769.1 m2 m-3 (average); for SEM methodology, 10586.6 m2 m-3. The BET value was higher than expected in reality, and the SEM method result was more suitable and used as data input in a mathematical modeling.

Effect of temperature decrease on anammox granular sludge: Shock and adaptation

Cryopreservation is one of the effective methods for the preservation of anammox granular sludge (AnGS). However, the effects of cooling pretreatment on AnGS are still unclear. In this study, the effects of temperature decrease on AnGS property were investigated by designing different cooling modes: constant at room temperature 20-25 °C (CK), sharp cooling to 4 °C (S4), -20 °C (S20) and stepwise cooling to 4 °C (A4), -20 °C (A20). The results showed that compared with CK, the cooling modes in S4, S20, A4 and A20 improved the physical preservability of AnGS, slowing down the changes of color, shape and structure; and elevated the preservation rate of functional bacteria Planctomycetes (phylum level) and Candidatus Brocadia (genus level). The preservation rate of live cells in different experimental groups was 48.4 ± 1.8%(CK), 61.1 ± 3.3%(S4), 37.8 ± 0.8%(S20), 81.7 ± 4.8%(A4), 61.9 ± 3.1%(A20), respectively. The Anaerobic Ammonium Oxidation Bacteria (AnAOB) in the stepwise cooling mode (A4 and A20) were found to enter the dormant state and form "dormant zoogloea", while the AnAOB in the sharp cooling mode (S4 and S20) were observed to enter the shock state with a little change. The findings in this work (especially the dormant state of AnAOB) are helpful to understand the effect of temperature decrease on AnGS and to promote the development of AnGS preservation technology.

Complex microbial nitrogen-cycling networks in three distinct anammox-inoculated wastewater treatment systems

Microbial nitrogen removal mediated by anaerobic ammonium oxidation (anammox) are cost-effective, yet it is time-consuming to accumulate the slow-growing anammox bacteria in conventional wastewater treatment plants (WWTPs). Inoculation of anammox enriched pellets is an effective way to establish anammox and achieve shortcut nitrogen removal in full-scale WWTPs. However, little is known about the complex microbial nitrogen-cycling networks in these anammox-inoculated WWTPs. Here, we applied metagenomic and metatranscriptomic tools to study the microbial nitrogen removal in three conventional WWTPs, which have been inoculated exogenous anammox pellets, representing partial-nitrification anammox (PNA) and nitrification-denitrification nitrogen removal processes. In the PNA system of Bali (BL), ammonia was partially oxidized by ammonia-oxidizing bacteria (AOB) Nitrosomonas and the oxidized nitrite and the remaining ammonium were directly converted to N₂ by anammox bacteria Ca. Brocadia and Ca. Kuenenia. In the nitrification-denitrification system of Wenshan (WS), ammonia-oxidizing archaea (AOA) Thaumarchaeota unexpectedly dominated the nitrifying community in the presence of AOB Nitrosomonas. Meanwhile, the biomass yield of Ca. Brocadia was likely inhibited by the high biodegradable organic compound input and limited by substrate competitions from AOA, AOB, complete ammonia oxidizers (comammox) Nitrospira, nitrite-oxidizing bacteria (NOB) Nitrospira, and heterotrophic denitrifiers. Unexpectedly, comammox Nitrospira was the predominant nitrifier in the presence of AOB Nitrosomonas in the organic carbon-rich nitrification-denitrification system of Linkou (LK). These results clearly showed that distinct active groups were working in concert for an effective nitrogen removal in different WWTPs. This study confirmed the feasibility of anammox application in ammonium-rich systems by direct inoculation of the exogenous anammox pellets and improved our understanding of microbial nitrogen cycling in anammox-driven conventional WWTPs from both physiochemical and omics perspectives.

Simultaneous nitrite and ammonium production in an autotrophic partial denitrification and ammonification of wastewaters containing thiocyanate

Various products are observed in biological oxidation and reduction of molecules containing elements of variable valence. The variability is caused by the diversity of microorganisms and their metabolic enzymes, which may develop into novel processes in wastewater treatment. The study aimed to develop a novel denitrification process forming nitrite and ammonium in wastewaters containing thiocyanate. High-efficiency nitrite and ammonium production was observed due to autotrophic partial denitrification and ammonification as a result of nitrate and thiocyanate removal. Nitrite, ammonium and sulfate were observed as the ultimate products. The increased NO₃^--N/SCN^--N ratio in the treated wastewater resulted in the decreased removal efficiency of nitrate, and the increased nitrate-to-nitrite transformation ratio and the ratio of NO₂^--N to NH₄⁺-N. Thiocyanate sulfur was oxidized to sulfate via intermediate elementary sulfur providing electron to nitrate or nitrite. The Thiobacillus genus dominated in the sludge providing ammonium and nitrite as substrate for the potentially anammox process.

Significance of pH control in anammox process performance at low temperature

Anaerobic ammonium oxidation (anammox) is an efficient process for biological nitrogen removal from wastewater. Common use of this technology is still limited by relatively high optimal temperature. Temperature and pH influence on the anammox process was widely studied, but the significance of pH control in the anammox performance at low temperature was omitted. Moreover up to now, these two parameters were analyzed separately without looking into the composite effects. Statistical approach was used to conduct an in-depth study of the individual and interactive influence of pH and low temperature on the anammox activity. Optimal pH was observed between 7.0 and 7.5, but results indicate that there is no statistically significant interaction between pH and temperature. However, it was observed that the optimal pH range narrows along with the temperature decrease, which means that the efficiency of the anammox process at low temperatures can be improved by correction and adequate control of pH.

Influence of temperature and pH on the anammox process: A review and meta-analysis

The anammox (anaerobic ammonium oxidation) process was considered a very efficient and economic wastewater treatment technology immediately after its discovery in 1995, thus research in this field was intensified. The anammox process is characterised by a high temperature optimum and is very sensitive to both temperature and pH fluctuations. The process can also be inhibited by many factors, including by its substrates, i.e. nitrite and ammonium (or its unionised forms: free ammonia and free nitrous acid). This paper presents a comprehensive study of the most important and recent findings on the influence of two parameters that are crucial in wastewater treatment, i.e. temperature and pH. Because both parameters may influence the anammox process simultaneously, a meta-analysis was conducted of the data from the literature. Although meta-analysis is commonly used in medical research, mathematical analysis of the literature data has become an interesting and important step in the environmental sciences. This paper presents information on the influence of both temperature and pH on process efficiency and microbial composition. Additionally, the responses of different operating systems on both temperature and pH changes are described. Moreover, the role of both adaptation to changed conditions and of pH control as well as indicated areas of process operation are discussed.