Research advances of ammonia oxidation microorganisms in wastewater: metabolic characteristics, microbial community, influencing factors and process applications

Symbiotic virus-bacteria interactions in biological treatment of coking wastewater manipulating bacterial physiological activities

Biological treatment is commonly used in coking wastewater (CWW) treatment. Prokaryotic microbial communities in CWW treatment have been comprehensively studied. However, viruses, as the critical microorganisms affecting microbial processes and thus engineering parameters, still remain poorly understood in CWW treatment context. Employing viromics sequencing, the composition and function of the viral community in CWW treatment were discovered, revealing novel viral communities and key auxiliary metabolic functions. Caudovirales appeared to be the predominant viral order in the oxic-hydrolytic-oxic (OHO) CWW treatment combination, showing relative abundances of 62.47 %, 56.64 % and 92.20 % in bioreactors O1, H and O2, respectively. At the family level, Myoviridae, Podoviridae and Siphoviridae mainly prevailed in bioreactors O1 and H while Phycodnaviridae dominated in O2. A total of 56.23-92.24% of novel viral contigs defied family-level characterization in this distinct CWW habitat. The virus-host prediction results revealed most viruses infecting the specific functional taxa Pseudomonas, Acidovorax and Thauera in the entire OHO combination, demonstrating the viruses affecting bacterial physiology and pollutants removal from CWW. Viral auxiliary metabolic genes (AMGs) were screened, revealing their involvement in the metabolism of contaminants and toxicity tolerance. In the bioreactor O1, AMGs were enriched in detoxification and phosphorus ingestion, where glutathione S-transferase (GSTs) and beta-ketoadipyl CoA thiolase (fadA) participated in biodegradation of polycyclic aromatic hydrocarbons and phenols, respectively. In the bioreactors H and O2, the AMGs focused on cell division and epicyte formation of the hosts, where GDPmannose 4,6-dehydratase (gmd) related to lipopolysaccharides biosynthesis was considered to play an important role in the growth of nitrifiers. The diversities of viruses and AMGs decreased along the CWW treatment process, pointing to a reinforced virus-host adaptive strategy in stressful operation environments. In this study, the symbiotic virus-bacteria interaction patterns were proposed with a theoretical basis for promoting CWW biological treatment efficiency. The findings filled the gaps in the virus-bacteria interactions at the full-scale CWW treatment and provided great value for understanding the mechanism of biological toxicity and sludge activity in industrial wastewater treatment.

Acidophilic partial nitrification (pH<6) facilitates ultra-efficient short-flow nitrogen transformation: Experimental validation and genomic insights

Partial nitrification (PN) represents an energy-efficient bioprocess; however, it often confronts challenges such as unstable nitrite accumulation, nitrite oxidizing bacteria shocks, and slow reaction rate. This study established an acidophilic PN with self-sustained pH as low as 5.36. Over 120-day monitoring, nitrite accumulation rate (NAR) was stabilized at more than 97.9 %, and an ultra-high ammonia oxidation rate of 0.81 kg/m3·d was achieved. Notably, least NAR of 77.8 % persisted even under accidental nitrite oxidizing bacteria invasion, aeration delay, alkalinity fluctuations, and cooling shocks. During processing, despite detrimental effects on bacterial diversity, there was a discernible increase in acid-tolerant bacteria responsible for nitrification. Candidatus Nitrosoglobus, gradually dominated in nitrifying guild (2.15 %), with the substantially reduction or disappearance of typical nitrifying microorganisms. Acidobacteriota, a key player in nitrogen cycling of soil, significantly increased from 0.45 % to 9.98 %, and its associated nitrogen metabolism genes showed a substantial 215 % rise. AmoB emerged as the most critical functional gene influencing acidophilic PN, exhibiting significantly higher unit gene expression than other nitrification genes. Blockade tricarboxylic acid cycle, DNA damage, and presence of free nitrous acid exert substantial effects on nitrite-oxidizing bacteria (NOB), serving as internal driving forces for acidophilic PN. This highlights the reliable potential for shortening nitrogen transformation process.

Utilization of microbial fuel cells as a dual approach for landfill leachate treatment and power production: a review

Landfill leachate, which is a complicated organic sewage water, presents substantial dangers to human health and the environment if not properly handled. Electrochemical technology has arisen as a promising strategy for effectively mitigating contaminants in landfill leachate. In this comprehensive review, we explore various theoretical and practical aspects of methods for treating landfill leachate. This exploration includes examining their performance, mechanisms, applications, associated challenges, existing issues, and potential strategies for enhancement, particularly in terms of cost-effectiveness. In addition, this critique provides a comparative investigation between these treatment approaches and the utilization of diverse kinds of microbial fuel cells (MFCs) in terms of their effectiveness in treating landfill leachate and generating power. The examination of these technologies also extends to their use in diverse global contexts, providing insights into operational parameters and regional variations. This extensive assessment serves the primary goal of assisting researchers in understanding the optimal methods for treating landfill leachate and comparing them to different types of MFCs. It offers a valuable resource for the large-scale design and implementation of processes that ensure both the safe treatment of landfill leachate and the generation of electricity. The review not only provides an overview of the current state of landfill leachate treatment but also identifies key challenges and sets the stage for future research directions, ultimately contributing to more sustainable and effective solutions in the management of this critical environmental issue.

Increases in the soil ammonia oxidizing phylotypes and their rechange due to long-term irrigation with wastewater

Wastewater irrigation is a common practice for agricultural systems in arid and semiarid zones, which can help to overcome water scarcity and contribute with nutrient inputs. Ammonia-oxidizing bacteria (AOB) and archaea (AOA) are key in the transformation of NH4+-N in soil and can be affected by variations in soil pH, EC, N and C content, or accumulation of pollutants, derived from wastewater irrigation. The objective of this study was to determine the changes in the ammonia oxidizing communities in agricultural soils irrigated with wastewater for different periods of time (25, 50, and 100 years), and in rainfed soils (never irrigated). The amoA gene encoding for the catalytic subunit of the ammonia monooxygenase was used as molecular reporter; it was quantified by qPCR and sequenced by high throughput sequencing, and changes in the community composition were associated with the soil physicochemical characteristics. Soils irrigated with wastewater showed up to five times more the abundance of ammonia oxidizers (based on 16S rRNA gene relative abundance and amoA gene copies) than those under rainfed agriculture. While the amoA-AOA: amoA-AOB ratio decreased from 9.8 in rainfed soils to 1.6 in soils irrigated for 100 years, indicating a favoring environment for AOB rather than AOA. Further, the community structure of both AOA and AOB changed during wastewater irrigation compared to rainfed soils, mainly due to the abundance variation of certain phylotypes. Finally, the significant correlation between soil pH and the ammonia oxidizing community structure was confirmed, mainly for AOB; being the main environmental driver of the ammonia oxidizer community. Also, a calculated toxicity index based on metals concentrations showed a correlation with AOB communities, while the content of carbon and nitrogen was more associated with AOA communities. The results indicate that wastewater irrigation influence ammonia oxidizers communities, manly by the changes in the physicochemical environment.

Bioaerosols in deodorization covers of wastewater treatment plants: Emission characteristics and health risks

Wastewater treatment plants (WWTPs) are the main source of bioaerosol emissions. The cover of deodorization within WWTPs serves not only to manage odors but also to limit the dispersion of bioaerosols. This study investigated the emission characteristics and exposure risks of bioaerosols inside deodorization covers from a WWTP in Northern China. The results revealed that the concentration of bacteria in bioaerosols ranged from 96 ± 8 to 706 ± 45 CFU/m3, with the highest concentration observed in the biochemical reaction tank. The predominant bacterial genera in bioaerosols within the odor control covers were Cetobacterium, Romboutsia, Bacteroides, Lactobacillus, and Tubricibacter, while the dominant fungal genera included Aspergillus, Alternaria, Fusarium, and Cladosporium. The main water-soluble ions in the air were NH4+, Ca2+, SO42-, and Cl-. SO42- was found to promote the survival of Cetobacterium, Brevibacterium, Fusarium, Penicillium, and Filobasidium, while Cl- exhibited inhibitory effects on most microorganisms in bioaerosols. Source tracker analysis indicated that wastewater was the primary source of bioaerosols in the biochemical reaction tank. The non-carcinogenic risk associated with bioaerosols within deodorization covers was less than 1 (2.34 × 10-9 to 3.08 × 10-2). FunGuild fungal functional prediction suggested that the abundance of animal pathogens was highest in the bioaerosols from the anaerobic sedimentation tank. BugBase phenotypic prediction showed that the abundance of potential pathogens in secondary sedimentation tank bioaerosols was the highest. This study effectively revealed the characteristics and sources of bioaerosols in the sewage and sludge treatment area under the deodorization cover, which provided a theoretical basis for enhancing the management and control of bioaerosols.

Towards low carbon demand and highly efficient nutrient removal: Establishing denitrifying phosphorus removal in anaerobic/anoxic/oxic + nitrification system

A two-sludge anaerobic/anoxic/oxic + nitrification system with simultaneous nitrogen and phosphorus removal was studied for enhanced low-strength wastewater treatment. After 158 days of operation, excellent NH4+-N, chemical oxygen demand (COD) and PO43--P removal (99.0 %, 90.0 % and 92.0 %, respectively) were attained under a low carbon/nitrogen ratio of 5, resulting in effluent NH4+-N, COD and PO43--P concentrations of 0.3, 30.0 and 0.5 mg/L, respectively. The results demonstrate that the anaerobic/anoxic/oxic sequencing batch reactor (A2-SBR) and nitrification sequencing batch reactor (N-SBR) had favorable denitrifying phosphorus removal and nitrification performance, respectively. High-throughput sequencing results indicate that the phosphate-accumulating organisms Dechloromonas (1.1 %) and Tetrasphaera (1.2 %) were enriched in the A2-SBR, while the ammonia-oxidizing bacteria Nitrosomonas (7.8 %) and the nitrite-oxidizing bacteria Nitrospira (18.1 %) showed excellent accumulation in the N-SBR. Further analysis via functional prediction revealed that denitrification is the primary pathway of nitrogen metabolism throughout the system. Overall, the system achieved low carbon and high efficiency nutrient removal.

Submerged macrophyte promoted nitrogen removal function of biofilms in constructed wetland

Biofilm is one of the important factors affecting nitrogen removal in constructed wetlands (CWs). However, the impact of submerged macrophyte on nitrogen conversion of biofilms on leaf of submerged macrophyte and matrix remains poorly understood. In this study, the CWs with Vallisneria natans and with artificial plant were established to investigate the effects of submerged macrophyte on nitrogen conversion and the composition of nitrogen-converting bacteria in leaf and matrix biofilms under high ammonium nitrogen (NH4+-N) loading. The 16S rRNA sequencing method was employed to explore the changes in bacterial communities in biofilms in CWs. The results showed that average removal rates of total nitrogen and NH4+-N in CW with V. natans reached 71.38% and 82.08%, respectively, representing increases of 24.19% and 28.79% compared with the control with artificial plant. Scanning electron microscope images indicated that high NH4+-N damaged the leaf cells of V. natans, leading to the cellular content release and subsequent increases of aqueous total organic carbon. However, the specific surface area and carrier function of V. natans were unaffected within 25 days. As a natural source of organic matters, submerged macrophyte provided organic matters for bacterial growth in biofilms. Bacterial composition analysis revealed the predominance of phylum Proteobacteria in CW with V. natans. The numbers of nitrifiers and denitrifiers in leaf biofilms reached 1.66 × 105 cells/g and 1.05 × 107 cells/g, as well as 2.79 × 105 cells/g and 7.41 × 107 cells/g in matrix biofilms, respectively. Submerged macrophyte significantly increased the population of nitrogen-converting bacteria and enhanced the expressions of nitrification genes (amoA and hao) and denitrification genes (napA, nirS and nosZ) in both leaf and matrix biofilms. Therefore, our study emphasized the influence of submerged macrophyte on biofilm functions and provided a scientific basis for nitrogen removal of biofilms in CWs.

Partial nitrification-denitrification and enrichment of paracoccus induced by iron-chitosan beads addition in an intermittently-aerated activated sludge system

Insufficient carbon source has become the main limiting factor for efficient nitrogen removal in wastewater treatment. In this study, an intermittently-aerated activated sludge system with iron-chitosan (Fe-CS) beads addition was proposed for nitrogen removal from low C/N wastewater. By adding Fe-CS beads, partial nitrification-denitrification (PND) process and significant enrichment of Paracoccus (with ability of iron reduction/ammonium oxidation/aerobic denitrification) were observed in the reactor. The accumulation rate of NO2--N reached 81.9 %, and the total nitrogen removal efficiency was improved to 93.9 % by shortening the aeration time. The higher activity of ammonium oxidizing bacteria and inhibited activity of nitrite-oxidizing bacteria in Fe-CS assisted system mediated the occurrence of PND. In contrast, the traditional nitrification and denitrification process occurred in the control group. The high-throughput sequencing analysis and metagenomic results confirmed that the addition of Fe-CS induced 77.8 % and 54.9 % enrichment of Paracoccus in sludge and Fe-CS beads, respectively, while almost no enrichment was observed in control group. Furthermore, with the addition of Fe-CS beads, the expression of genes related to outer membrane porin, cytochrome c, and TCA was strengthened, thereby enhancing the electron transport of Fe(Ⅱ) (electron donor) and Fe(Ⅲ) (electron acceptor) with pollutants in the periplasm. This study provides new insights into the direct enrichment of iron-reducing bacteria and its PND performance induced by the Fe-CS bead addition. It therefore offers an appealing strategy for low C/N wastewater treatment.

Multidrug-resistant plasmid RP4 inhibits the nitrogen removal capacity of ammonia-oxidizing archaea, ammonia-oxidizing bacteria, and comammox in activated sludge

In wastewater treatment plants (WWTPs), ammonia oxidation is primarily carried out by three types of ammonia oxidation microorganisms (AOMs): ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and comammox (CMX). Antibiotic resistance genes (ARGs), which pose an important public health concern, have been identified at every stage of wastewater treatment. However, few studies have focused on the impact of ARGs on ammonia removal performance. Therefore, our study sought to investigate the effect of the representative multidrug-resistant plasmid RP4 on the functional microorganisms involved in ammonia oxidation. Using an inhibitor-based method, we first evaluated the contributions of AOA, AOB, and CMX to ammonia oxidation in activated sludge, which were determined to be 13.7%, 41.1%, and 39.1%, respectively. The inhibitory effects of C2H2, C8H14, and 3,4-dimethylpyrazole phosphate (DMPP) were then validated by qPCR. After adding donor strains to the sludge, fluorescence in situ hybridization (FISH) imaging analysis demonstrated the co-localization of RP4 plasmids and all three AOMs, thus confirming the horizontal gene transfer (HGT) of the RP4 plasmid among these microorganisms. Significant inhibitory effects of the RP4 plasmid on the ammonia nitrogen consumption of AOA, AOB, and CMX were also observed, with inhibition rates of 39.7%, 36.2%, and 49.7%, respectively. Moreover, amoA expression in AOB and CMX was variably inhibited by the RP4 plasmid, whereas AOA amoA expression was not inhibited. These results demonstrate the adverse environmental effects of the RP4 plasmid and provide indirect evidence supporting plasmid-mediated conjugation transfer from bacteria to archaea.

Enhancing nitrogen removal performance through intermittent aeration in continuous plug-flow anaerobic/aerobic/anoxic process treating low-strength municipal sewage

Advanced nitrogen removal cannot be achieved through the conventional biological nitrogen removal process, which requires higher carbon sources and aeration energy. The proposal of intermittent aeration in the aerobic chambers offered an innovative approach to enhance nitrogen removal in low carbon-to-nitrogen ratio (C/N) municipal sewage, using a plug-flow reactor with anaerobic/aerobic/anoxic (AOA) process. Due to the effective utilization of internal carbon sources through the intermittent aeration, the total inorganic nitrogen removal efficiency (NRE) increased to 77.9 ± 3.2 % with the mean aerobic hydraulic retention time of only 3.2 h and a low C/N of 3.3 during the operation of 210 days. Polyhydroxyalkanoates dominated the nitrogen removal in this AOA system, accounting for 48.0 %, primarily occurring in the alternant aerobic/anoxic chambers. Moreover, the microbial community structure remained unchanged while the NRE increased to 77.9 %. This study provided an efficient and economic strategy for the continuous plug-flow AOA process.

Effects of flow rate and wastewater concentration on the transformation of nitrogen in sediment-water system of sewage pipelines

In this work, the transformation law of nitrogen in sediment-water system under different flow rates and wastewater concentrations were investigated in a simulated sewage pipeline system. Results showed that the different flow rates and wastewater concentrations in the pipeline caused differences in microbial community in sediments and nitrogen transformation. When the flow rate increased from 0.05 to 0.2 m/s, the scouring effect was enhanced, resulting in higher concentrations of NH4 + -N and NO3 - -N in the overlying water. At 0.2 m/s, the relative abundance of Clostridium_sensu_stricto_1 in sediments was higher, resulting in a greater conversion of amino acid nitrogen (AAN) to NH4 + -N. Meanwhile, many denitrifying bacteria (Trichococcus, Dechloromonas, norank_f__norank_o__Gaiellales, Thiobacillus) had high relative abundance in the sediments, and the denitrification process was common. When the wastewater concentration was high, the nitrification reaction was great in overlying and interstitial water. Moreover, the ammoniation process was great in the sediments, and the variation flux of AAN was large (remarkably reduced). PRACTITIONER POINTS: AAN transformed to NH4 + -N in sediment under different flow rate and concentration. Scouring was enhanced at 0.2 m/s, increasing nitrogen contents in overlying water. Difference in microbial community led to more AAN conversion to NH4 + -N at 0.2 m/s. The ammoniation process was greater in sediment at a high concentration of sewage. NH4 + -N migrated from overlying water to sediment at a high concentration of sewage.

The effect of ammonia concentration on the treatment of bio electrochemical leachate using MFCs technology

Microbial fuel cells (MFCs) have garnered attention in bio-electrochemical leachate treatment systems. The most common forms of inorganic ammonia nitrogen are ammonium ([Formula: see text]) and free ammonia. Anaerobic digestion can be inhibited in both direct (changes in environmental conditions, such as fluctuations in temperature or pH, can indirectly hinder microbial activity and the efficiency of the digestion process) and indirect (inadequate nutrient levels, or other conditions that indirectly compromise the microbial community's ability to carry out anaerobic digestion effectively) ways by both kinds. The performance of a double-chamber MFC system-composed of an anodic chamber, a cathode chamber with fixed biofilm carriers (carbon felt material), and a Nafion 117 exchange membrane is examined in this work to determine the impact of ammonium nitrogen ([Formula: see text]) inhibition. MFCs may hold up to 100 mL of fluid. Therefore, the bacteria involved were analysed using 16S rRNA. At room temperature, with a concentration of 800 mg L-1 of ammonium nitrogen and 13,225 mg L-1 of chemical oxygen demand (COD), the study produced a considerable power density of 234 mWm-3. It was found that [Formula: see text] concentrations above 800 mg L-1 have an inhibitory influence on power output and treatment effectiveness. Multiple routes removed the most nitrogen ([Formula: see text]-N: 87.11 ± 0.7%, NO2 -N: 93.17 ± 0.2% and TN: 75.24 ± 0.3%). Results from sequencing indicate that the anode is home to a rich microbial community, with anammox (6%), denitrifying (6.4%), and electrogenic bacteria (18.2%) making up the bulk of the population. Microbial fuel cells can efficiently and cost-effectively execute anammox, a green nitrogen removal process, in landfill leachate.

Enhanced nitrogen removal in immersed rotating self-aerated biofilm reactor: nitrogen removal pathway and microbial mechanism

To achieve energy-efficient treatment of the rural wastewater with satisfying performance, a novel immersed rotating self-aerated biofilm reactor (iRSABR) was proposed in this study. The iRSABR system showed better biofilm renewal performance and higher microbial activity. The effect of different regulation strategies on the iRSABR system was investigated in this study. The 70% immersion ratio and 4 r/min rotation speed (stage III) exhibited the best performance, with a total nitrogen removal efficiency of 86% and a simultaneous nitrification-denitrification (SND) rate of 76%, along with the highest electron transport system activity. The nitrogen removal pathway revealed that the SND was achieved through autotrophic/heterotrophic nitrification and aerobic/anoxic denitrification. The regulation strategy in the iRSABR system established a synergistic microbial community with main functional bacteria of nitrification (Nitrosomonas), anoxic denitrification (Flavobacterium, Pseudoxanthomonas), and aerobic denitrification (Thauera). This study highlighted the feasibility and adaptability of the iRSABR system toward energy-efficient rural wastewater treatment.