Bacterial community structure in rotating biological contactor treating coke wastewater in relation to medium composition.

Biological wastewater treatment using biofilm systems is an effective way to treat difficult wastewater, such as coke wastewater. The information about the structure and the dynamics of this microbial community in biofilm, which are responsible for wastewater treatment, is relevant in the context of treatment efficacy and the biochemical potential to remove various pollutants. However, physico-chemical factors can influence the biofilm community significantly, causing performance disturbances. Therefore, we decided to examine the structure of microbial community in rotating biological contactor (RBC) biofilm during coke wastewater treatment and to investigate the possible shift in the community structure caused by the feeding medium change from synthetic to real coke wastewater. The experiment performed with high-throughput next-generation sequencing (NGS) revealed that bacteria commonly present in wastewater treatment plant (WWTP) systems, responsible for nitrite oxidizing, such as Nitrospira or Nitrobacter, were absent or below detection threshold, while Nitrosomonas, responsible for ammonia oxidizing, was detected in a relatively small number especially after shift to real coke wastewater. This research indicates that medium change could cause the change from autotrophic into heterotrophic nitrification led by Acinetobacter. Moreover, biofilm systems can be also a potential source of bacteria possessing high biochemical potential for pollutants removal but less known in WWTP systems, as well as potentially pathogenic microorganisms.

Effects of the Wastewater Flow Rate on Interactions between the Genus Nitrosomonas and Diverse Populations in an Activated Sludge Microbiome.

The present study characterized the interactions of microbial populations in activated sludge systems during the operational period after an increase in the wastewater flow rate and consequential ammonia accumulation using a 16S rRNA gene sequencing-based network analysis. Two hundred microbial populations accounting for 81.8% of the total microbiome were identified. Based on a co-occurrence analysis, Nitrosomonas-type ammonia oxidizers had one of the largest number of interactions with diverse bacteria, including a bulking-associated Thiothrix organism. These results suggest that an increased flow rate has an impact on constituents by changing ammonia concentrations and also that Nitrosomonas- and Thiothrix-centric responses are critical for ammonia removal and microbial community recovery.

Impact of Heavy Metal Pollution on Ammonia Oxidizers in Soils in the Vicinity of a Tailings Dam, Baotou, China.

Soil heavy metal pollution has received increasing attention due to their toxicity to soil microorganisms. We have analyzed the effects of heavy metal pollution on ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in soils in the vicinity of a tailings dam of Baotou region, China. Results showed that AOB were dominated with Nitrosomonas-like clusters, while AOA was dominated by group1.1b (Nitrososphaera cluster). Single Cd and Cr contents, as well as compound heavy metal pollution levels, had a significant negative impact on soil potential nitrification rate and both diversities of AOA and AOB. No clear relationship was found between any single heavy metal and abundance of AOA or AOB. But compound pollution could significantly decrease AOA abundance. The results indicated that heavy metal pollution had an obviously deleterious effect on the abundance, diversity, activity and composition of ammonia oxidizers in natural soils.

Single-stage autotrophic nitrogen removal process at high loading rate: granular reactor performance, kinetics, and microbial characterization.

For the possible highest performance of single-stage combined partial nitritation/anammox (PNA) process, a continuous complete-mix granular reactor was operated at progressively higher nitrogen loading rate. The variations in bacterial community structure of granules were also characterized using high-throughput pyrosequencing, to give a detail insight to the relationship between reactor performance and functional organism abundance within completely autotrophic nitrogen removal system. In 172 days of operation, a superior total nitrogen (TN) removal rate over 3.9 kg N/(m3/day) was stable implemented at a fixed dissolved oxygen concentration of 1.9 mg/L, corresponding to the maximum specific substrate utilization rate of 0.36/day for TN based on the related kinetics modeling. Pyrosequencing results revealed that the genus Nitrosomonas responsible for aerobic ammonium oxidation was dominated on the granule surface, which was essential to offer the required niche for the selective enrichment of anammox bacteria (genus Candidatus Kuenenia) in the inner layer. And the present of various heterotrophic organisms with general functions, known as fermentation and denitrification, could not be overlooked. In addition, it was believed that an adequate excess of ammonium in the bulk liquid played a key role in maintaining process stability, by suppressing the growth of nitrite-oxidizing bacteria through dual-substrate competitions.

Dynamics of the diversity and structure of the overall and nitrifying microbial community in activated sludge along gradient copper exposures.

Diversity and composition of the microbial community, especially the nitrifiers, are essential to the treatment efficiency of wastewater in activated sludge systems. Heavy metals commonly present in the wastewater influent such as Cu can alter the community structure of nitrifiers and lower their activity. However, the dynamics of microbial community along a gradient of metal exposure have largely been unexplored, partially due to the limitations in traditional molecular methods. This study explored the dynamics regarding the diversity and community structures of overall and nitrifying microbial communities in activated sludge under intermittent Cu gradient loadings using Illumina sequencing. We created a new local nitrifying bacterial database for sequence BLAST searches. High Cu loadings (>10.9 mg/L) impoverished microbial diversity and altered the microbial community. Overall, Proteobacteria was the predominant phylum in the activated sludge system, in which Zoogloea, Thauera, and Dechloromonas (genera within the Rhodocyclaceae family of the Beta-proteobacteria class) were the dominant genera in the presence of Cu. The abundance of unclassified bacteria at the phylum level increased substantially with increasing Cu loadings. Nitrosomonas and Nitrospira were the predominant nitrifiers. The nitrifying bacterial community changed through increasing abundance and shifting to Cu-tolerant species to reduce the toxic effects of Cu. Our local nitrifying bacterial database helped to improve the resolution of bacterial identification. Our results provide insights into the dynamics of microbial community in response to various metal concentrations in activated sludge systems and improve our understanding regarding the effect of metals on wastewater treatment efficiency.

A pilot-scale study on PVA gel beads based integrated fixed film activated sludge (IFAS) plant for municipal wastewater treatment.

In the present study, a pilot-scale reactor incorporating polyvinyl alcohol gel beads as biomass carrier and operating in biological activated sludge mode (a combination of moving bed biofilm reactor (MBBR) and activated sludge) was investigated for the treatment of actual municipal wastewater. The results, during a monitoring period of 4 months, showed effective removal of chemical oxygen demand (COD), biological oxygen demand (BOD) and NH3-N at optimum conditions with 91%, ∼92% and ∼90% removal efficiencies, respectively. Sludge volume index (SVI) values of activated sludge varied in the range of 25-72 mL/g, indicating appreciable settling characteristics. Furthermore, soluble COD and BOD in the effluent of the pilot plant were reduced to levels well below discharge limits of the Punjab Pollution Control Board, India. A culture dependent method was used to enrich and isolate abundant heterotrophic bacteria in activated sludge. In addition to this, 16S rRNA genes analysis was performed to identify diverse dominant bacterial species in suspended and attached biomass. Results revealed that Escherichia coli, Pseudomonas sp. and Nitrosomonas communis played a significant role in biomass carrier, while Acinetobactor sp. were dominant in activated sludge of the pilot plant. Identification of ciliated protozoa populations rendered six species of ciliates in the plant, among which Vorticella was the most dominant.

Insights into the effect of mixed engineered nanoparticles on activated sludge performance.

In this study, the effects, fate and transport of ENPs in wastewater treatment plants (WWTP) were investigated using three parallel pilot WWTPs operated under identical conditions. The WWTPs were spiked with (i) an ENP mixture consisting of silver oxide, titanium dioxide and zinc oxide, and (ii) bulk metal salts. The third plant served as control (unspiked). ENP effects were evaluated for (i) bulk contaminant removal, (ii) activated sludge (AS) process performance, (iii) microbial community structure and dynamics and (iv) microbial inhibition. ENPs showed a strong affinity for biosolids and induced a specific oxygen uptake rate two times higher than the control. The heterotrophic biomass retained its ability to nitrify and degrade organic matter. However, non-recovery of ammonia- and nitrite-oxidizing bacteria such as Nitrosomonas, Nitrobacter or Nitrospira in the ENP spiked reactors suggests selective inhibitory effects. The results further suggest that ENPs and metal salts have antimicrobial properties which can reduce synthesis of extracellular polymeric substances and therefore floc formation. Scanning electron microscopy evidenced selective damage to some microbes, whereas lipid fingerprinting and 454 pyrosequencing indicated a temporal shift in the microbial community structure and diversity. Acidovorax, Rhodoferax, Comamonas and Methanosarcina were identified as nano-tolerant species. Competitive growth advantage of the nano-tolerant species influenced the removal processes and unlike other xenobiotic compounds, ENPs can hasten the natural selection of microbial species in AS.

Nitrosomonas stercoris sp. nov., a Chemoautotrophic Ammonia-Oxidizing Bacterium Tolerant of High Ammonium Isolated from Composted Cattle Manure.

Among ammonia-oxidizing bacteria, Nitrosomonas eutropha-like microbes are distributed in strongly eutrophic environments such as wastewater treatment plants and animal manure. In the present study, we isolated an ammonia-oxidizing bacterium tolerant of high ammonium levels, designated strain KYUHI-S(T), from composted cattle manure. Unlike the other known Nitrosomonas species, this isolate grew at 1,000 mM ammonium. Phylogenetic analyses based on 16S rRNA and amoA genes indicated that the isolate belonged to the genus Nitrosomonas and formed a unique cluster with the uncultured ammonia oxidizers found in wastewater systems and animal manure composts, suggesting that these ammonia oxidizers contributed to removing higher concentrations of ammonia in strongly eutrophic environments. Based on the physiological and phylogenetic data presented here, we propose and call for the validation of the provisional taxonomic assignment Nitrosomonas stercoris, with strain KYUHI-S as the type strain (type strain KYUHI-S(T) = NBRC 110753(T) = ATCC BAA-2718(T)).

Isolation and characterization of a thermotolerant ammonia-oxidizing bacterium Nitrosomonas sp. JPCCT2 from a thermal power station.

A thermotolerant ammonia-oxidizing bacterium strain JPCCT2 was isolated from activated sludge in a thermal power station. Cells of JPCCT2 are short non-motile rods or ellipsoidal. Molecular phylogenetic analysis of 16S rRNA gene sequences demonstrated that JPCCT2 belongs to the genus Nitrosomonas with the highest similarity to Nitrosomonas nitrosa Nm90 (100%), Nitrosomonas sp. Nm148 (99.7%), and Nitrosomonas communis Nm2 (97.7%). However, G+C content of JPCCT2 DNA was 49.1 mol% and clearly different from N. nitrosa Nm90, 47.9%. JPCCT2 was capable of growing at temperatures up to 48 °C, while N. nitrosa Nm90 and N. communis Nm2 could not grow at 42°C. Moreover, JPCCT2 grew similarly at concentrations of carbonate 0 and 5 gL(-1). This is the first report that Nitrosomonas bacterium is capable of growing at temperatures higher than 37°C.

Diversity and dynamics of ammonia-oxidizing bacterial communities in a sponge-based trickling filter treating effluent from a UASB reactor.

Changes in ammonia-oxidizing bacterial (AOB) population dynamics were examined in a new sponge-based trickling filter (TF) post-upflow anaerobic sludge blanket (UASB) reactor by denaturating gradient gel electrophoresis (DGGE), and these changes were linked to relevant components influencing nitrification (chemical oxygen demand (COD), nitrogen (N)). The sponge-based packing media caused strong concentration gradients along the TF, providing an ecological selection of AOB within the system. The organic loading rate (OLR) affected the population dynamics, and under higher OLR or low ammonium-nitrogen (NH4(+)-N) concentrations some AOB bands disappeared, but maintaining the overall community function for NH4(+)-N removal. The dominant bands present in the upper portions of the TF were closely related to Nitrosomonas europaea and distantly affiliated to Nitrosomonas eutropha, and thus were adapted to higher NH4(+)-N and organic matter concentrations. In the lower portions of the TF, the dominant bands were related to Nitrosomonas oligotropha, commonly found in environments with low levels of NH4(+)-N. From a technology point of view, changes in AOB structure at OLR around 0.40-0.60 kgCOD m(-3) d(-1) did not affect TF performance for NH4(+)-N removal, but AOB diversity may have been correlated with the noticeable stability of the sponge-based TF for NH4(+)-N removal at low OLR. This study is relevant because molecular biology was used to observe important features of a bioreactor, considering realistic operational conditions applied to UASB/sponge-based TF systems.

Impact of food to microorganism (F/M) ratio and colloidal chemical oxygen demand on nitrification performance of a full-scale membrane bioreactor treating thin film transistor liquid crystal display wastewater.

This study investigated impact of food to microorganism (F/M) ratio and colloidal chemical oxygen demand (COD) on nitrification performance in one full-scale membrane bioreactor (MBR) treating monoethanolamine (MEA)/dimethyl sulfoxide (DMSO)-containing thin film transistor liquid crystal display (TFT-LCD) wastewater. Poor nitrification was observed under high organic loading and high colloidal COD conditions, suggesting that high F/M ratio and colloidal COD situations should be avoided to minimize their negative impacts on nitrification. According to the nonmetric multidimensional scaling (NMS) statistical analyses on terminal restriction fragment length polymorphism (T-RFLP) results of ammonia monooxygenase (amoA) gene, the occurrence of Nitrosomonas oligotropha-like ammonia oxidizing bacteria (AOB) was positively related to successful nitrification in the MBR systems, while Nitrosomonas europaea-like AOB was positively linked to nitrification rate, which can be attributed to the high influent total nitrogen condition. Furthermore, Nitrobacter- and Nitrospira-like nitrite oxidizing bacteria (NOB) were both abundant in the MBR systems, but the continuously low nitrite environment is likely to promote the growth of Nitrospira-like NOB.

Colonization of freshwater biofilms by nitrifying bacteria from activated sludge.

Effluents from wastewater treatment plants (WWTPs) containing micro-organisms and residual nitrogen can stimulate nitrification in freshwater streams. We hypothesized that different ammonia-oxidizing (AOB) and nitrite-oxidizing (NOB) bacteria present in WWTP effluents differ in their potential to colonize biofilms in the receiving streams. In an experimental approach, we monitored biofilm colonization by nitrifiers in ammonium- or nitrite-fed microcosm flumes after inoculation with activated sludge. In a field study, we compared the nitrifier communities in a full-scale WWTP and in epilithic biofilms downstream of the WWTP outlet. Despite substantially different ammonia concentrations in the microcosms and the stream, the same nitrifiers were detected by fluorescence in situ hybridization in all biofilms. Of the diverse nitrifiers present in the WWTPs, only AOB of the Nitrosomonas oligotropha/ureae lineage and NOB of Nitrospira sublineage I colonized the natural biofilms. Analysis of the amoA gene encoding the alpha subunit of ammonia monooxygenase of AOB revealed seven identical amoA sequence types. Six of these affiliated with the N. oligotropha/ureae lineage and were shared between the WWTP and the stream biofilms, but the other shared sequence type grouped with the N. europaea/eutropha and N. communis lineage. Measured nitrification activities were high in the microcosms and the stream. Our results show that nitrifiers from WWTPs can colonize freshwater biofilms and confirm that WWTP-affected streams are hot spots of nitrification.

Analysis of microbial population dynamics in a partial nitrifying SBR at ambient temperature.

In this study, a lab-scale partial nitrifying sequencing batch reactor (SBR) was developed to investigate partial nitrification at ambient temperature (16-22 °C). Techniques of denaturing gradient gel electrophoresis (DGGE), cloning, and fluorescence in situ hybridization (FISH) were utilized simultaneously to study microbial population dynamics. Partial nitrification was effectively achieved in response to shifts of influent ammonium concentrations. DGGE results showed that higher ammonia concentration referred to lower ammonia-oxidizing bacteria (AOB) diversity in the SBR. Phylogenetic analysis revealed that all the predominant AOB was affiliated with Nitrosomonas genus. FISH analysis illustrated AOB was the predominant nitrifying bacteria of microbial compositions when SBR achieved partial nitrification (PN) at ambient temperature.

Minimization of nitrous oxide emission from anoxic-oxic biological nitrogen removal process: effect of influent COD/NH4+ ratio and feeding strategy.

Nitrous oxide (N(2)O) is an important greenhouse gas and biological nitrogen removal process of wastewater treatment plant is one of its sources. Mechanisms of N(2)O emissions from anoxic-oxic biological nitrogen removal process were investigated and minimizations of N(2)O emissions were carried out from the aspect of organic carbon supplement, i.e., influent COD/NH4+ ratio (C/N ratio) and feeding strategy. Results showed that during anoxic-oxic biological nitrogen removal process, most of the N(2)O emissions occurred during the oxic phase, and both nitrifier denitrification and aerobic hydroxylamine oxidation pathways were possible mechanisms responsible for N(2)O emissions. N(2)O conversion rate decreased from 6.0% to 1.3% when the influent C/N ratio was increased from 7.5 to 14.5. This was mainly because of decrease in the abundance of Nitrosomonas-like ammonia oxidizing bacteria. Step feeding and external carbon source addition could reduce N(2)O conversion rate by 66.6% and 12.0%, respectively. Both of them were feasible methods for minimizing N(2)O emission from wastewater treatment process. The low N(2)O emission of step feeding was because of its high dissolved oxygen (DO) and low ammonium concentrations during the oxic phase, while the minimization effect of external carbon source addition was ascribed to its high nitrogen removal efficiency.

Correlating microbial community structure and composition with aeration intensity in submerged membrane bioreactors by 454 high-throughput pyrosequencing.

For understanding of the microbial community structure and composition under different aeration intensities, 454 high-throughput pyrosequencing was applied to analyze the 16S rRNA gene of bacteria in two submerged membrane bioreactors (MBRs) under low (R(L)) and high aeration (R(H)) conditions. In total, 7818 (R(L)) and 9353 (R(H)) high-quality reads were obtained, and 1230 (R(L)) and 924 (R(H)) operational taxonomic units (OTUs) were generated at 3% cutoff level, respectively. 454 pyrosequencing could also reveal the minority bacteria that were hardly detected by the conventional molecular methods. Although the core populations were shared with highly functional organization (>80%), clear differences between the samples in the two MBRs were revealed by richness-diversity indicators and Venn analyses. Notably, microbial diversity was decreased under high aeration condition, and the evolution of the populations was observed mainly in the shared OTUs. Moreover, specific comparison down to the class and genus level showed that the relative abundances of ß-Proteobacteria and γ-Proteobacteria in the R(H) community were respectively decreased by 41.5% and 66.6%, consistent with the observed membrane fouling mitigation during the reactor operation. It was also found that Nitrospira and Nitrosomonas, being nitrite oxidizing bacteria (NOB) and ammonium oxidizing bacteria (AOB), were the dominant phylogenetic groups at the genus level of both reactors, and that the high ratio of NOB to AOB populations well supported the complete ammonium oxidation performance in the two reactors. Although some populations of NOB and AOB decreased with the increase of aeration intensity, the functional stability of the nitrification process was less affected, probably due to the low influent substrate concentration and the high level of functional organization.

Responses of ammonia-oxidizing archaeal and betaproteobacterial populations to wastewater salinity in a full-scale municipal wastewater treatment plant.

The diversity and abundance of ammonia-oxidizing Betaproteobacteria and archaea were investigated in a full-scale municipal wastewater treatment plant where the wastewater conductivity level varied considerably (due to seawater salinity intrusion) during this study between 2004 and 2007. Based on the quantitative polymerase chain reaction of ammonia monooxygenase subunit A (amoA) genes, an increase in the ammonia oxidizing bacteria amoA gene copies occurred with a decrease in the wastewater salinity level. A corresponding decrease in the average ammonia-oxidizing archaea to bacteria ratio, from 1.22 (2004 and 2005), 0.17 (2006), and then to 0.07 (2007), was observed. Phylogenetic analyses on amoA gene sequences indicated that Nitrosomonas marina-like ammonia oxidizing bacteria and Thaumarcheota Ⅰ.1a (marina group) ammonia-oxidizing archaea were dominant when the wastewater salinity level fluctuated at high values with an average of 4.83 practical salinity unit (psu), while Nitrosomonas urea-like ammonia oxidizing bacteria and Thaumarcheota Ⅰ.1b (soil group) ammonia-oxidizing archaea became dominant when the wastewater salinity decreased to a more stable lower level with an average of 1.93 psu. Based on the amoA gene-based terminal restriction fragment length polymorphism analyses, results from this study demonstrated that the observed shift in ammonia oxidizing bacteria and archaea populations is likely caused by a change of the wastewater salinity level.

Reactor performance in terms of COD and nitrogen removal and bacterial community structure of a three-stage rotating bioelectrochemical contactor.

Integrating microbial fuel cell (MFC) into rotating biological contactor (RBC) creates an opportunity for enhanced removal of COD and nitrogen coupled with energy generation from wastewater. In this study, a three-stage rotating bioelectrochemical contactor (referred to as RBC-MFC unit) integrating MFC with RBC technology was constructed for simultaneous removal of carbonaceous and nitrogenous compounds and electricity generation from a synthetic medium containing acetate and ammonium. The performance of the RBC-MFC unit was compared to a control reactor (referred to as RBC unit) that was operated under the same conditions but without current generation (i.e. open-circuit mode). The effect of hydraulic loading rate (HLR) and COD/N ratio on the performance of the two units was investigated. At low (3.05 gCOD g⁻¹N) and high COD/N ratio (6.64 gCOD g⁻¹N), both units achieved almost similar COD and ammonia-nitrogen removal. However, the RBC-MFC unit achieved significantly higher denitrification and nitrogen removal compared to the RBC unit indicating improved denitrification at the cathode due to current flow. The average voltage under 1000 Ω external resistance ranged between 0.03 and 0.30 V and between 0.02 and 0.21 V for stages 1 and 2 of the RBC-MFC unit. Pyrosequencing analysis of bacterial 16S rRNA gene revealed high bacterial diversity at the anode and cathode of both units. Genera that play a role in nitrification (Nitrospira; Nitrosomonas), denitrification (Comamonas; Thauera) and electricity generation (Geobacter) were identified at the electrodes. Geobacter was only detected on the anode of the RBC-MFC unit. Nitrifiers and denitrifiers were more abundant in the RBC-MFC unit compared to the RBC unit and were largely present on the cathode of both units suggesting that most of the nitrogen removal occurred at the cathode.

[Quantitative and qualitative analysis of total bacteria and ammonia-oxidizing bacteria in Buji River in wet season].

Microbial community structure and biomass in river water can reflect the situation of water quality in some extent. Nitrogen removal was mainly achieved by the nitrification and denitrification processes, and ammonia oxidation catalyzed by ammonia-oxidizing bacteria (AOB) is the first and rate-limiting step of nitrification. To explore the AOB community structure and biomass in nitrogen polluted river, water samples were collected from Buji River (Shenzhen) in wet season. Quantification of 16S rRNA copy numbers of total bacteria and AOB were performed by real-time PCR, and the microbial community structures were studied by denaturing gradient gel electrophoresis (DGGE). The results showed that the number of total bacterial 16S rRNA changed from 4.73 x 10(10) - 3.90 x 10(11) copies x L(-1) in the water samples. The copy numbers of AOB varied from 5.44 x 10(6) - 5.96 x 10(8)copies x L(-1). Redundancy discrimination analysis (RDA) showed that the main factors affecting the structure and the numbers of bacteria were different. For total bacteria, nitrate influenced the biomass significantly (P < 0.05) while nitrogen and heavy metals (Mn and Zn) were the main factors affecting the microbial community structures (P < 0.05). For AOB, ammonia and Zn were the main factors influencing the biomass while ammonia nitrogen and heavy metals (Mn and Zn) were the main factors affecting the microbial community structures. 16S rDNA sequences from the water samples indicated that the bacteria generally belonged to Epsilon-Proteobacteria, Gamma-Proteobacteria, Beta-Proteobacteria, and Delta-Proteobacteria. Nitrosomonas sp. and Nitrosospira sp. were the main AOB. Cluster analysis showed that water pollution in downstream resulted in evident difference in microbial community structure between upstream and downstream water samples.

Characteristics of aerobic and anaerobic ammonium-oxidizing bacteria in the hyporheic zone of a contaminated river.

Both ß-proteobacterial aerobic ammonium-oxidizing bacteria (AOB) and anaerobic ammonium-oxidizing (ANAMMOX) bacteria were investigated in the hyporheic zone of a contaminated river in China containing high ammonium levels and low chemical oxygen demand. Fluorescence in-situ hybridization (FISH), denaturing gradient gel electrophoresis (DGGE) and cloning-sequencing were employed in this study. FISH analysis illustrated that AOB (average population of 3.5 %) coexisted with ANAMMOX bacteria (0.7 %). The DGGE profile revealed a high abundance and diversity of bacteria at the water-air-soil interface rather than at the water-soil interface. The redundancy analysis correlated analysis showed that the diversity of ANAMMOX bacteria was positively related to the redox potential. The newly detected sequences of ANAMMOX organisms principally belonged to the genus Candidatus "Brocadia", while most ammonia monooxygenase subunit-A gene amoA sequences were affiliated with Nitrosospira and Nitrosomonas. These results suggest that the water-air-soil interface performs an important function in the nitrogen removal process and that the bioresources of AOB and ANAMMOX bacteria can potentially be utilized for the eutrophication of rivers.