Predominance of ammonia-oxidizing archaea on granular activated carbon used in a full-scale advanced drinking water treatment plant

Autotrophic growth activity of complete ammonia oxidizers in an upflow biological contact filter for drinking water treatment

Biological filters effectively remove ammonium from drinking water via nitrification. In a pilot-scale upflow biological contact filter (U-BCF), complete ammonia oxidizers (comammox), which are capable of oxidizing ammonia to nitrate in one cell, were more abundant than ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). However, little information is available on the contribution of comammox to nitrification. In this study, we evaluated the autotrophic growth activity of comammox associated with biological activated carbon (BAC) in a U-BCF by DNA-stable isotope probing (DNA-SIP). BAC samples collected from the U-BCF were continuously fed mineral medium containing 0.14 mg N L-1 ammonium and 12C- or 13C-labeled bicarbonate for 20 days. DNA-SIP analysis revealed that comammox (clades A and B) as well as AOA assimilated bicarbonate after 10 days of incubation, proving that dominant comammox could contribute to nitrification. Contrarily, AOB remained inactive throughout the observation period. Amplicon sequencing of the 13C-labeled DNA fractions of comammox revealed that specific genotypes other than the most dominant genotype in the original sample were more enriched under the incubation condition for the DNA-SIP experiment. Thus, dominant genotypes of comammox in a U-BCF might utilize organic nitrogen to fuel nitrification in ammonia-limited environments.

Multi-scale Investigation of Ammonia-Oxidizing Microorganisms in Biofilters Used for Drinking Water Treatment

Ammonia-oxidizing microorganisms (AOMs) include ammonia-oxidizing bacteria (AOB), archaea (AOA), and Nitrospira spp. sublineage II capable of complete ammonia oxidation (comammox). These organisms can affect water quality not only by oxidizing ammonia to nitrite (or nitrate) but also by cometabolically degrading trace organic contaminants. In this study, the abundance and composition of AOM communities were investigated in full-scale biofilters at 14 facilities across North America and in pilot-scale biofilters operated for 18 months at a full-scale water treatment plant. In general, the relative abundance of AOM in most full-scale biofilters and in the pilot-scale biofilters was as follows: AOB > comammox Nitrospira > AOA. The abundance of AOB in the pilot-scale biofilters increased with increasing influent ammonia concentration and decreasing temperature, whereas AOA and comammox Nitrospira exhibited no correlations with these parameters. The biofilters affected AOM abundance in the water passing through the filters via collecting and shedding but exhibited a minor influence on the composition of AOB and Nitrospira sublineage II communities in the filtrate. Overall, this study highlights the relative importance of AOB and comammox Nitrospira compared to AOA in biofilters and the influence of filter influent water quality on AOM in biofilters and their release into the filtrate.

Ammonia-oxidizing archaea and complete ammonia-oxidizing Nitrospira in water treatment systems

Nitrification, the oxidation of ammonia to nitrate via nitrite, is important for many engineered water treatment systems. The sequential steps of this respiratory process are carried out by distinct microbial guilds, including ammonia-oxidizing bacteria (AOB) and archaea (AOA), nitrite-oxidizing bacteria (NOB), and newly discovered members of the genus Nitrospira that conduct complete ammonia oxidation (comammox). Even though all of these nitrifiers have been identified within water treatment systems, their relative contributions to nitrogen cycling are poorly understood. Although AOA contribute to nitrification in many wastewater treatment plants, they are generally outnumbered by AOB. In contrast, AOA and comammox Nitrospira typically dominate relatively low ammonia environments such as drinking water treatment, tertiary wastewater treatment systems, and aquaculture/aquarium filtration. Studies that focus on the abundance of ammonia oxidizers may misconstrue the actual role that distinct nitrifying guilds play in a system. Understanding which ammonia oxidizers are active is useful for further optimization of engineered systems that rely on nitrifiers for ammonia removal. This review highlights known distributions of AOA and comammox Nitrospira in engineered water treatment systems and suggests future research directions that will help assess their contributions to nitrification and identify factors that influence their distributions and activity.

Distinct comammox Nitrospira catalyze ammonia oxidation in a full-scale groundwater treatment bioreactor under copper limited conditions

Microbial ammonia oxidation is the initial nitrification step used in biological nitrogen-removal during water treatment processes, and the discovery of complete ammonia-oxidizing (comammox) bacteria added a novel member to this functional group. It is important to identify and understand the predominant microorganisms responsible for ammonium removal in biotechnological process design and optimization. In this study, we used a full-scale bioreactor to treat ammonium in groundwater (9.3 ± 0.5 mg NH₄⁺-N/L) and investigated the key ammonia-oxidizing prokaryotes present. The groundwater ammonium was stably and efficiently oxidized throughout ∼700 days of bioreactor operation. 16S rRNA gene amplicon sequencing of the bioreactor community showed a high abundance of Nitrospira (12.5-45.9%), with the dominant sequence variant (3.5-37.8%) most closely related to Candidatus Nitrospira nitrosa. Furthermore, analyses of amoA, the marker gene for ammonia oxidation, indicated the presence of two distinct comammox Nitrospira populations, however, the relative abundance of only one of these populations was strongly correlated to ammonia oxidation rates and was robustly expressed. After 380 days of operation copper wires were immersed into the reactor at 0.04-0.06 m²/m³ tank, which caused a gradual abundance increase of one discrete comammox Nitrospira population. However, further increase of the copper dosing (0.08 m²/m³ tank) inverted the most abundant ammonia-oxidizing population to Nitrosomonas sp. These results indicate that comammox Nitrospira were capable of efficient ammonium removal in groundwater without exogenous nutrients, but copper addition can stimulate comammox Nitrospira or lead to dominance of Nitrosomonas depending on dosage.

Diverse and active archaea communities occur in non-disinfected drinking water systems-Less activity revealed in disinfected and hot water systems

The knowledge about the members of active archaea communities in DWDS is limited. The current understanding is based on high-throughput 16S ribosomal RNA gene (DNA-based) amplicon sequencing that reveals the diversity of active, dormant, and dead members of the prokaryote (bacteria, archaea) communities. The sequencing primers optimized for bacteria community analysis may underestimate the share of the archaea community. This study characterized archaea communities at five full-scale drinking water distribution systems (DWDS), representing a variety of drinking water production units (A-E); A&B use artificially recharged non-disinfected groundwater (ARG), the other DWDS's supplied water disinfected by using ultraviolet (UV) light and chlorine compounds, C&D were surface waterworks and E was a ground waterworks. For the first time for archaea community analyses, this study employed the archaea-specific high-throughput sequencing primers for 16S ribosomal RNA (rRNA) as a target (reverse-transcribed cDNA; an RNA-based approach) in addition to the previously used 16S rRNA gene target (rDNA; a DNA-based approach) to reveal the active fraction of the archaea present in DWDS. The archaea community structure in varying environmental conditions in the water and biofilm of the five DWDSs were investigated by taking into consideration the system properties (cold or hot water system) and water age (distance from the treatment plants) in samples from each season of one year. The RNA-based archaea amplicon reads were obtained mostly from cold water samples from DWDSs (A-B) distributing water without disinfection where the DNA-based and RNA-based analysis created separate clusters in a weighted beta-diversity analysis. The season and location in DWDS A further affected the diversity of these archaea communities as was seen by different clusters in beta-diversity plots. The recovery of archaea reads was not adequate for analysis in any of the disinfected samples in DWDSs C-E or non-disinfected hot water in DWDSs A-B when utilizing RNA-based template. The metabolically active archaea community of DWDSs thus seemed to be effectively controlled by disinfection of water and in the hot water systems by the temperature. All biofilms regardless of DWDS showed lower species richness values (mainly Nitrososphaeria class) than non-disinfected water from DWDSs A-B where several archaea classes occurred (e.g. Woesearchaeia, Nitrososphaeria, Micrarchaeia, Methanomicrobia, Iairchaeia, Bathyarchaeia) indicating only part of the archaea members were able to survive in biofilms. Thus, Archaea has been shown as a significant part of normal DWDS biota, and their role especially in non-disinfected DWDS may be more important than previously considered.

Influence of operational conditions and wastewater properties on the removal of organic micropollutants through ozonation

The objective of this study was to evaluate the influence of operational conditions and wastewater properties on the removal of pharmaceuticals, contrast media and antibiotics through ozonation, in order to facilitate the optimization of treatment and its implementation on a full scale. Pilot-scale ozone oxidation trials were performed on treated wastewater, before and after post-precipitation, over a seven-month period, including summer and winter months. Hydraulic retention times as short as 7 min were found to be sufficient for organic micropollutant removal. A short hydraulic retention time reduces both investment costs and land use. Neither the choice of ozone dispersion method, a static mixer or a Venturi injector, nor the wastewater temperature had any significant effect on the removal efficiency of organic micropollutants, however, higher removal was achieved after on-site post-precipitation with aluminum chloride.

Microbial abundance and community composition in biofilms on in-pipe sensors in a drinking water distribution system

Collecting biofilm samples from drinking water distribution systems (DWDSs) is challenging due to limited access to the pipes during regular operations. We report here the analysis of microbial communities in biofilm and water samples collected from sensors installed in a DWDS where monochloramine is used as a residual disinfectant. A total of 52 biofilm samples and 14 bulk water samples were collected from 17 pipe sections representing different water ages. Prokaryotic genome copies (bacterial and archaeal 16S rRNA genes, Mycobacterium spp., ammonia-oxidizing bacteria (AOB), and cyanobacteria) were quantified with droplet digital PCR, which revealed the abundance of these genes in both biofilm and water samples. Prokaryotic 16S rRNA gene sequencing analysis was carried out for a subset of the samples (12 samples from four sites). Mycobacterium and AOB species were dominant in the DWDS sections with low water age and sufficient residual monochloramine, whereas Nitrospira species (nitrite-oxidizing bacteria) dominated in the sections with higher water age and depleted monochloramine level, suggesting the occurrence of nitrification in the studied DWDS. The present study provides novel information on the abundance and identity of prokaryotes in biofilms and water in a full-scale operational DWDS.

Hydroxylamine and the nitrogen cycle: A review

Aerobic ammonium oxidizing bacteria were first isolated more than 100 years ago and hydroxylamine is known to be an intermediate. The enzymatic steps involving hydroxylamine conversion to nitrite are still under discussion. For a long time it was assumed that hydroxylamine was directly converted to nitrite by a hydroxylamine oxidoreductase. Recent enzymatic evidences suggest that the actual product of hydroxylamine conversion is NO and a third, yet unknown, enzyme further converts NO to nitrite. More recently, ammonium oxidizing archaea and complete ammonium oxidizing bacteria were isolated and identified. Still the central nitrogen metabolism of these microorganisms presents to researchers the same puzzle: how hydroxylamine is transformed to nitrite. Nitrogen losses in the form of NO and N₂O have been identified in all three types of aerobic ammonium oxidizing microorganisms and hydroxylamine is known to play a significant role in the formation. Yet, the pathways and the factors promoting the greenhouse gas emissions are to be fully characterized. Hydroxylamine also plays a yet poorly understood role on anaerobic ammonium oxidizing bacteria and is known to inhibit nitrite oxidizing bacteria. In this review, the role of this elusive intermediate in the metabolism of different key players of the nitrogen cycle is discussed, as well as the putative importance of hydroxylamine as a key nitrogen metabolite for microbial interactions within microbial communities and engineered systems. Overall, for the first time putting together the acquired knowledge about hydroxylamine and the nitrogen cycle over the years in a review, setting potential hypothesis and highlighting possible next steps for research.

Effect of Flow Configuration on Nitrifiers in Biological Activated Carbon Filters for Potable Water Production

Up-flow biological activated carbon (BAC) filters have been empirically employed in drinking water treatment plants (DWTPs) to address the challenges of its down-flow counterparts (e.g., high head loss and insufficient use of BAC beds), yet their performances and mechanisms toward ammonia removal are not fully evaluated. This study characterized the occurrence, distribution, and diversities of nitrifiers in up-flow and down-flow BAC filters by investigating 18 full-scale drinking water treatment trains in different geographic locations. Quantitative polymerase chain reaction analysis of gene markers of target microorganisms demonstrated higher numbers of total bacteria, ammonia-oxidizing bacteria (AOB), and Nitrospira in the up-flow filters relative to the down-flow filters (P < 0.05), implying enhanced biological activities and nitrification potential within up-flow filters. The dominance of ammonia-oxidizing archaea (AOA) over AOB (i.e., 1.3-4.0 log₁₀ gene copies higher) in 17 BAC filters illustrated the critical role of AOA in drinking water nitrification. Stratification of biomass was mainly found in the down-flow filters rather than the up-flow filters, suggesting better mixing of filter media across up-flow filter beds. Analysis of similarity results revealed that the AOA and Nitrospira community compositions were mainly affected by water sources and locations (P < 0.05) but not flow configurations. These results provide insight into nitrification mechanisms in BAC filters with different flow configurations in real-world DWTPs.

Temperature-Dependent Ammonium Removal Capacity of Biological Activated Carbon Used in a Full-Scale Drinking Water Treatment Plant

Nitrification is a key function of biological activated carbon (BAC) filters for drinking water treatment. It is empirically known that the nitrification activity of BAC filters depends on water temperature, potentially resulting in the leakage of ammonium from BAC filters when the water temperature decreases. However, the ammonium removal capacity of BAC filters and factors governing the capacity remain unknown. This study employed a bench-scale column assay to determine the volumetric ammonium removal rate (VARR) of BAC collected from a full-scale drinking water treatment plant. VARR was determined at a fixed loading rate under different conditions. Seasonal variations of the VARR as well as impacts of the water matrix and water temperature on ammonium removal were quantitatively analyzed. While the VARR in an inorganic medium at 25 °C was maintained even during low water temperature periods and during breakpoint chlorination periods, the water matrix factor reduced the VARR in ozonated water at 25 °C by 33% on average. The VARR in ozonated water was dependent on water temperature, indicating that the microbial activity of BAC did not adapt to low water temperature. The Arrhenius equation was applied to reveal the relationship between VARR and water temperature. The actual ammonium removal performance of a full-scale BAC filter was predicted. VARR is useful for water engineers to reexamine the loading and filter depth of BAC filters.

Surface ammonium loading rate shifts ammonia-oxidizing communities in surface water-fed rapid sand filters

Nitrification is important in drinking water treatment plants (DWTPs) for ammonia removal and is widely considered as a stepwise process mediated by ammonia- and nitrite-oxidizing microorganisms. The recent discovery of complete ammonia oxidizers (comammox) has challenged the long-held assumption that the division of metabolic labor in nitrification is obligate. However, little is known about the role of comammox Nitrospira in DWTPs. Here, we explored the relative importance of comammox Nitrospira, canonical ammonia-oxidizing archaea (AOA) and bacteria (AOB) in 12 surface water-fed rapid sand filters (RSFs). Quantitative PCR results showed that all the three ammonia-oxidizing guilds had the potential to dominate nitrification in DWTPs. Spearman's correlation and redundancy analysis revealed that the surface ammonium loading rate (SLR) was the key environmental factor influencing ammonia-oxidizing communities. Comammox Nitrospira were likely to dominate the nitrification under a higher SLR. PCR and phylogenetic analysis indicated that most comammox Nitrospira belonged to clade A, with clade B comammox Nitrospira almost absent. This work reveals obvious differences in ammonia-oxidizing communities between surface water-fed and groundwater-fed RSFs. The presence of comammox Nitrospira can support the stability of drinking water production systems under high SLR and warrants further investigation of their impact on drinking water quality.

Nitrifying niche differentiation in biofilms from full-scale chloraminated drinking water distribution system

Tropical conditions favour the auto-decomposition of monochloramine (MCA) leading to disinfectant decay and free ammonia in drinking water distribution systems (DWDS); thus, they promote the growth of nitrifiers and the development of biofilms on the inner-pipe surface. Biofilms can adversely impact the provision of safe and biologically stable water. Moreover, there is a general lack of understanding of the role of microbial communities in DWDS in regions with warm temperatures and no distinct seasons. Here, we report a survey on biofilms from full-scale monochloraminated DWDS in a highly urbanised metropolis using next generation sequencing tools. The monitoring campaign consisted of sampling biofilms and bulk waters from 21 in-service pipes. We characterized the microbial community with emphasis on nitrifying bacteria and archaea using 16S rRNA gene amplicon sequencing and potential nitrification activity. Samples grouped into two clusters, characterized by their low (Cluster LD) and high (Cluster HD) α-diversity. Both clusters harbour microorganisms related to nitrification: i) Nitrosomonas (24.9-68.8%), an ammonia oxidising bacterium (AOB) that dominated Cluster LD, and ii) a co-aggregation of genus Nitrospira (9.8-32.5%), a nitrite oxidising bacterium (NOB), and Thaumarchaeota (1.4-10.9%), chemolithotrophic ammonia oxidising (AOA) archaea that were among the most abundant OTUs in Cluster HD. Activity tests performed with fresh biofilm samples confirmed that these two clusters represent distinctive biofilm niches performing different stages of the nitrification process. Cluster LD correlated with a high concentration of MCA, which caused dysbiosis and resulted in high unevenness of the cluster. In cluster HD, with more biomass, chemical reactions involving nitrite increased the MCA demand, releasing ammonia and allowing more nitrifiers to grow, like AOA and NOB. From this study, we conclude that an MCA residual gradient along the DWDS drives and shapes the microbial community assembly and should be considered when designing effective disinfection strategies.

Abundance and activity of ammonia oxidizing archaea and bacteria in bulk water and biofilm in water supply systems practicing chlorination and chloramination: Full and laboratory scale investigations

The abundance and nitrification activity of ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) in bulk water and biofilm in chloraminated and chlorinated water supply systems were investigated. The abundance of AOB varied between cold and warm periods while that was the case for AOA only in biofilm. Lower ammonia concentrations favored the abundance of AOA over AOB. AOA and AOB were found more in distal zones of the distribution system (DS). Higher numbers of AOA and AOB were observed in DS associated with chloramination compared to those associated with chlorination. Significant positive correlations between ammonia-N in bulk water and AOA indicate a possibility of involvement of AOA in nitrification in DS. A separate laboratory-based experiment simulating DS condition was conducted to understand the effects of chlorine and chloramine dosages and temperature on AOA and AOB. AOA were inhibited less than AOB in the presence of lower concentrations of chlorine and chloramine (1.5 and 2.0 mg/L chlorine; 0.05-0.1 and 0.3-0.4 mg/L chloramine) while both of them were not detected at higher dosages (2.5 mg/L chlorine and 1.5-1.6 mg/L chloramine). At a low temperature (10-12 °C), chloramine and chlorine provided similar inhibition trends in which AOB were inhibited more than AOA. At a high temperature (25 °C), chloramine was less inhibitory to AOA and AOB than chlorine.

Consecutive ultrafiltration and silica adsorption for recovery of extracellular antibiotic resistance genes from an urban river

The dissemination of antibiotic resistance (AR) has attracted global attention because of the increasing antibiotic treatment failure it has caused. Through natural transformation, a live bacterium takes up extracellular DNA (exDNA), which facilitates AR dissemination. However, recovery of exDNA from water samples is challenging. In this study, we validated a consecutive ultrafiltration-based protocol to simultaneously recover intracellular DNA (inDNA), dissolved exDNA (Dis_exDNA, dissolved in the bulk water), and adsorbed exDNA (Ads_exDNA, adsorbed to the surfaces of suspended particles). Using hollow fiber ultrafiltration (HFUF), all DNA fractions were concentrated from environmental water samples, after which Dis_exDNA (supernatant) was separated from inDNA and Ads_exDNA (pellets) using centrifugation. Ads_exDNA was washed off from the pellets with proteinase K and sodium phosphate buffer. Dis_exDNA and Ads_exDNA were further concentrated using centrifugal ultrafiltration, from which silica binding was performed. inDNA was extracted from washed pellets with a commercial kit. For inDNA, HFUF showed recovery efficiencies of 96.5 ± 18.5% and 88.0 ± 2.0% for total cells and cultured Escherichia coli, respectively (n = 3). To represent all possible DNA fragments in water environment, exDNA with different lengths (10.0, 4.0, 1.0, and 0.5 kbp) were spiked to test the recovery efficiencies for Dis_exDNA. The whole process achieved 62.2%-62.9% recovery for 10 and 4 kbp exDNA, and 38.8%-44.5% recovery for 1.0 and 0.5 kbp exDNA. Proteinase K treatment enhanced the recovery of Ads_exDNA by 4.0-10.7 times. The protocol was applied to water samples from an urban river in Tokyo, Japan. The abundance of AR genes (ARGs) in inDNA, Dis_exDNA, and Ads_exDNA increased downstream of wastewater treatment plants. ARGs in Ads_exDNA and Dis_exDNA accounted for 1.8%-26.7% and 0.03%-20.9%, respectively, of the total DNA, implying that Ads_exDNA and Dis_exDNA are nonnegligible potential pools for the horizontal transfer of ARGs.

Separating and Characterizing Functional Nitrogen Degraders via Magnetic Nanoparticle-Mediated Isolation

Magnetic nanoparticle-mediated isolation (MMI) is a new method for isolating active functional microbes from complex microorganisms without substrate labeling. In this study, the composition and properties of magnetic nanoparticles (MNPs) were characterized by a number of techniques, indicating that MNPs have characteristics such as microinterfaces and can be efficiently fixed on the surface of microbial cells. It also introduced the MMI technology in activated sludge after stable long-term treatment. With further addition of promotor carbon sources, the enrichment of the functional nitrogen degraders in MMI was significantly higher than in samples without MNPs, showing the advantages of MMI in identifying the active degraders. Redundancy analysis (RDA) also showed that the functional nitrogen degraders such as Comamonadaceae_unclassified and Thiobacillus absolutely dominated in situ ammonia degradation, and the change in dominant genera had the same trend as the degradation rate of ammonia nitrogen. In the magnetically functionalized system, the separated functional nitrogen degraders significantly improved ammonia nitrogen degradation efficiency, making it basically stable at more than 80%, up to 91.6%. These results prove that the complex flora created after the addition of MNPs is more adaptable to newly introduced pollutants, and MMI is a powerful tool for studying pollutant-degrading microorganisms under in situ conditions.

Spatiotemporal shifts of ammonia-oxidizing archaea abundance and structure during the restoration of a multiple pond and plant-bed/ditch wetland

Ammonia-oxidizing archaea (AOA) microorganisms have been increasingly found in aquatic and terrestrial environments. These microorganisms make vital contributions to ammonia oxidation in such systems. However, their community succession characteristics in man-made wetland ecosystems have scarcely been reported. We assessed the AOA's spatiotemporal shifts in the sediments of a constructed wetland (CW) - the Shijiuyang constructed wetland (SJY-CW) - in China from the third year (2011) to the fifth year (2013) of the CW operation. The SJY-CW is composed of a pretreatment pond, a multiple plant-bed/ditch system, and a post-treatment pond. Results showed that AOA abundance in the pre- and post-treatment ponds remained invariant through 2011-2012 and decreased in 2013, while the abundance in the plant-bed/ditch system decreased gradually with wetland operation. The AOA abundance in 2013 was one order of magnitude lower than that through 2011-2012, and the AOA abundance in the plant-bed/ditch system was generally higher than that in the pre- and post-treatment ponds from 2011 to 2013. AOA diversity showed little temporal differentiation with a slightly decreasing trend for community richness index Chao1 and diversity index Shannon H' from 2011 to 2013. The AOA community was dominated by the Nitrososphaera cluster accompanied by an increasing Nitrosopumilus cluster and Nitrososphaera sister cluster within the wetland operation. Hierarchical clustering and redundancy analysis verified the horizontal shifts of AOA communities. The shifts occurred preferentially in the central plant-bed/ditch system. The operational duration of the wetland became a key factor influencing AOA abundance and community shift in SJY-CW sediments.

Density and distribution of nitrifying guilds in rapid sand filters for drinking water production: Dominance of Nitrospira spp

We investigated the density and distribution of total bacteria, canonical Ammonia Oxidizing Bacteria (AOB) (Nitrosomonas plus Nitrosospira), Ammonia Oxidizing Archaea (AOA), as well as Nitrobacter and Nitrospira in rapid sand filters used for groundwater treatment. To investigate the spatial distribution of these guilds, filter material was sampled at four drinking water treatment plants (DWTPs) in parallel filters of the pre- and after-filtration stages at different locations and depths. The target guilds were quantified by qPCR targeting 16S rRNA and amoA genes. Total bacterial densities (ignoring 16S rRNA gene copy number variation) were high and ranged from 10⁹ to 10¹⁰ per gram (10¹⁵ to 10¹⁶ per m³) of filter material. All examined guilds, except AOA, were stratified at only one of the four DWTPs. Densities varied spatially within filter (intra-filter variation) at two of the DWTPs and in parallel filters (inter-filter variation) at one of the DWTPs. Variation analysis revealed random sampling as the most efficient strategy to yield accurate mean density estimates, with collection of at least 7 samples suggested to obtain an acceptable (below half order of magnitude) density precision. Nitrospira was consistently the most dominant guild (5-10% of total community), and was generally up to 4 orders of magnitude more abundant than Nitrobacter and up to 2 orders of magnitude more abundant than canonical AOBs. These results, supplemented with further analysis of the previously reported diversity of Nitrospira in the studied DWTPs based on 16S rRNA and nxrB gene phylogeny (Gülay et al., 2016; Palomo et al., 2016), indicate that the high Nitrospira abundance is due to their comammox (complete ammonia oxidation) physiology. AOA densities were lower than AOB densities, except in the highly stratified filters, where they were of similar abundance. In conclusion, rapid sand filters are microbially dense, with varying degrees of spatial heterogeneity, which requires replicate sampling for a sufficiently precise determination of total microbial community and specific population densities. A consistently high Nitrospira to bacterial and archaeal AOB density ratio suggests that non-canonical pathways for nitrification may dominate the examined RSFs.

A review: Driving factors and regulation strategies of microbial community structure and dynamics in wastewater treatment systems

The performance and stabilization of biological wastewater treatment systems ¹are closely related to the microbial community structure and dynamics. In this paper, the effects and mechanisms of influent composition, process configuration, operating parameters (dissolved oxygen [DO], pH, hydraulic retention time [HRT] and sludge retention time [SRT]) and environmental condition (temperature) to the change of microbial community structure and process performance (nitrification, denitrification, biological phosphorus removal, organics mineralization and utilization, etc.) are critically reviewed. Furthermore, some strategies for microbial community structure regulation, mainly bioaugmentation, process adjustment and operating parameters optimization, applied in the current wastewater treatment systems are also discussed. Although the recent studies have strengthened our understanding on the relationship between microbial community structure and wastewater treatment process performance, how to fully tap the microbial information, optimize the microbial community structure and maintain the process performance in wastewater treatment systems are still full of challenges.

Spatial and temporal analogies in microbial communities in natural drinking water biofilms

Biofilms are ubiquitous throughout drinking water distribution systems (DWDS), playing central roles in system performance and delivery of safe clean drinking water. However, little is known about how the interaction of abiotic and biotic factors influence the microbial communities of these biofilms in real systems. Results are presented here from a one-year study using in situ sampling devices installed in two operational systems supplied with different source waters. Independently of the characteristics of the incoming water and marked differences in hydraulic conditions between sites and over time, a core bacterial community was observed in all samples suggesting that internal factors (autogenic) are central in shaping biofilm formation and composition. From this it is apparent that future research and management strategies need to consider the specific microorganisms found to be able to colonise pipe surfaces and form biofilms, such that it might be possible to exclude these and hence protect the supply of safe clean drinking water.

Diversity, abundance and activity of ammonia-oxidizing microorganisms in fine particulate matter

Increasing ammonia emissions could exacerbate air pollution caused by fine particulate matter (PM_2.5). Therefore, it is of great importance to investigate ammonia oxidation in PM_2.5. This study investigated the diversity, abundance and activity of ammonia oxidizing archaea (AOA), ammonia oxidizing bacteria (AOB) and complete ammonia oxidizers (Comammox) in PM_2.5 collected in Beijing-Tianjin-Hebei megalopolis, China. Nitrosopumilus subcluster 5.2 was the most dominant AOA. Nitrosospira multiformis and Nitrosomonas aestuarii were the most dominant AOB. Comammox were present in the atmosphere, as revealed by the occurrence of Candidatus Nitrospira inopinata in PM_2.5. The average cell numbers of AOA, AOB and Ca. N. inopinata were 2.82 × 10⁴, 4.65 × 10³ and 1.15 × 10³ cell m^-3 air, respectively. The average maximum nitrification rate of PM_2.5 was 0.14 μg (NH₄⁺-N) [m³ air·h]^-1. AOA might account for most of the ammonia oxidation, followed by Comammox, while AOB were responsible for a small part of ammonia oxidation. Statistical analyses showed that Nitrososphaera subcluster 4.1 was positively correlated with organic carbon concentration, and Nitrosomonas eutropha showed positive correlation with ammonia concentration. Overall, this study expanded our knowledge concerning AOA, AOB and Comammox in PM_2.5 and pointed towards an important role of AOA and Comammox in ammonia oxidation in PM_2.5.

Depth investigation of rapid sand filters for drinking water production reveals strong stratification in nitrification biokinetic behavior

The biokinetic behavior of NH4(+) removal was investigated at different depths of a rapid sand filter treating groundwater for drinking water preparation. Filter materials from the top, middle and bottom layers of a full-scale filter were exposed to various controlled NH4(+) loadings in a continuous-flow lab-scale assay. NH4(+) removal capacity, estimated from short term loading up-shifts, was at least 10 times higher in the top than in the middle and bottom filter layers, consistent with the stratification of Ammonium Oxidizing Bacteria (AOB). AOB density increased consistently with the NH4(+) removal rate, indicating their primarily role in nitrification under the imposed experimental conditions. The maximum AOB cell specific NH4(+) removal rate observed at the bottom was at least 3 times lower compared to the top and middle layers. Additionally, a significant up-shift capacity (4.6 and 3.5 times) was displayed from the top and middle layers, but not from the bottom layer at increased loading conditions. Hence, AOB with different physiological responses were active at the different depths. The biokinetic analysis predicted that despite the low NH4(+) removal capacity at the bottom layer, the entire filter is able to cope with a 4-fold instantaneous loading increase without compromising the effluent NH4(+). Ultimately, this filter up-shift capacity was limited by the density of AOB and their biokinetic behavior, both of which were strongly stratified.

Investigation of Archaeal and Bacterial community structure of five different small drinking water networks with special regard to the nitrifying microorganisms

Total microbial community structure, and particularly nitrifying communities inhabiting five different small drinking water networks characterized with different water physical and chemical parameters was investigated, using cultivation-based methods and sequence aided Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis. Ammonium ion, originated from well water, was only partially oxidized via nitrite to nitrate in the drinking water distribution systems. Nitrification occurred at low ammonium ion concentration (27-46μM), relatively high pH (7.6-8.2) and over a wide range of dissolved oxygen concentrations (0.4-9.0mgL(-1)). The nitrifying communities of the distribution systems were characterized by variable most probable numbers (2×10(2)-7.1×10(4) MPN L(-1)) and probably originated from the non-treated well water. The sequence aided T-RFLP method revealed that ammonia-oxidizing microorganisms and nitrite-oxidizing Bacteria (Nitrosomonas oligotropha, Nitrosopumilus maritimus, and Nitrospira moscoviensis, 'Candidatus Nitrospira defluvii') were present in different ratios in the total microbial communities of the distinct parts of the water network systems. The nitrate generated by nitrification was partly utilized by nitrate-reducing (and denitrifying) Bacteria, present in low MPN and characterized by sequence aided T-RFLP as Comamonas sp. and Pseudomonas spp. Different environmental factors, like pH, chemical oxygen demand, calculated total inorganic nitrogen content (moreover nitrite and nitrate concentration), temperature had important effect on the total bacterial and archaeal community distribution.

Retention of titanium dioxide nanoparticles in biological activated carbon filters for drinking water and the impact on ammonia reduction

Given the increasing discoveries related to the eco-toxicity of titanium dioxide (TiO2) nanoparticles (NPs) in different ecosystems and with respect to public health, it is important to understand their potential effects in drinking water treatment (DWT). The effects of TiO2 NPs on ammonia reduction, ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in biological activated carbon (BAC) filters for drinking water were investigated in static and dynamic states. In the static state, both the nitrification potential and AOB were significantly inhibited by 100 μg L(-1) TiO2 NPs after 12 h (p < 0.05), and the threshold decreased to 10 μg L(-1) with prolonged exposure (36 h, p < 0.05). However, AOA were not considerably affected in any of the tested conditions (p > 0.05). In the dynamic state, different amounts of TiO2 NP pulses were injected into three pilot-scale BAC filters. The decay of TiO2 NPs in the BAC filters was very slow. Both titanium quantification and scanning electron microscope analysis confirmed the retention of TiO2 NPs in the BAC filters after 134 days of operation. Furthermore, the TiO2 NP pulses considerably reduced the performance of ammonia reduction. This study identified the retention of TiO2 NPs in BAC filters and the negative effect on the ammonia reduction, suggesting a potential threat to DWT by TiO2 NPs.

Shifts in the pelagic ammonia-oxidizing microbial communities along the eutrophic estuary of Yong River in Ningbo City, China

Aerobic ammonia oxidation plays a key role in the nitrogen cycle, and the diversity of the responsible microorganisms is regulated by environmental factors. Abundance and composition of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) were investigated in the surface waters along an environmental gradient of the Yong River in Ningbo, East China. Water samples were collected from three pelagic zones: (1) freshwaters in the urban canals of Ningbo, (2) brackish waters in the downstream Yong River, and (3) coastal marine water of Hangzhou Bay. Shifts in activity and diversity of the ammonia-oxidizing microorganisms occurred simultaneously with changes in environmental factors, among which salinity and the availabilities of ammonium and oxygen. The AOA abundance was always higher than that of AOB and was related to the ammonia oxidation activity. The ratios of AOA/AOB in the brackish and marine waters were significantly higher than those found in freshwaters. Both AOA and AOB showed similar community compositions in brackish and marine waters, but only 31 and 35% similarity, respectively, between these waters and the urban inland freshwaters. Most of AOA-amoA sequences from freshwater were affiliated with sequences obtained from terrestrial environments and those collected from brackish and coastal areas were ubiquitous in marine, coastal, and terrestrial ecosystems. All AOB from freshwaters belonged to Nitrosomonas, and the AOB from brackish and marine waters mainly belonged to Nitrosospira.

Influence of water quality on nitrifier regrowth in two full-scale drinking water distribution systems

The potential for regrowth of nitrifying microorganisms was monitored in 2 full-scale chloraminated drinking water distribution systems in Ontario, Canada, over a 9-month period. Quantitative PCR was used to measure amoA genes from ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA), and these values were compared with water quality parameters that can influence nitrifier survival and growth, including total chlorine, ammonia, temperature, pH, and organic carbon. Although there were no severe nitrification episodes, AOB and AOA were frequently detected at low concentrations in samples collected from both distribution systems. A culture-based presence-absence test confirmed the presence of viable nitrifiers. AOB were usually present in similar or greater numbers than AOA in both systems. As well, AOB showed higher regrowth potential compared with AOA in both systems. Statistically significant correlations were measured between several water quality parameters of relevance to nitrification. Total chlorine was negatively correlated with both nitrifiers and heterotrophic plate count (HPC) bacteria, and ammonia levels were positively correlated with nitrifiers. Of particular importance was the strong correlation between HPC and AOB, which reinforced the usefulness of HPC as an operational parameter to measure general microbiological conditions in distribution systems.

The Bacterial Communities of Full-Scale Biologically Active, Granular Activated Carbon Filters Are Stable and Diverse and Potentially Contain Novel Ammonia-Oxidizing Microorganisms

The bacterial community composition of the full-scale biologically active, granular activated carbon (BAC) filters operated at the St. Paul Regional Water Services (SPRWS) was investigated using Illumina MiSeq analysis of PCR-amplified 16S rRNA gene fragments. These bacterial communities were consistently diverse (Shannon index, >4.4; richness estimates, >1,500 unique operational taxonomic units [OTUs]) throughout the duration of the 12-month study period. In addition, only modest shifts in the quantities of individual bacterial populations were observed; of the 15 most prominent OTUs, the most highly variable population (a Variovorax sp.) modulated less than 13-fold over time and less than 8-fold from filter to filter. The most prominent population in the profiles was a Nitrospira sp., representing 13 to 21% of the community. Interestingly, very few of the known ammonia-oxidizing bacteria (AOB; <0.07%) and no ammonia-oxidizing Archaea were detected in the profiles. Quantitative PCR of amoA genes, however, suggested that AOB were prominent in the bacterial communities (amoA/16S rRNA gene ratio, 1 to 10%). We conclude, therefore, that the BAC filters at the SPRWS potentially contained significant numbers of unidentified and novel ammonia-oxidizing microorganisms that possess amoA genes similar to those of previously described AOB.

Temporal and spatial stability of ammonia-oxidizing archaea and bacteria in aquarium biofilters

Nitrifying biofilters are used in aquaria and aquaculture systems to prevent accumulation of ammonia by promoting rapid conversion to nitrate via nitrite. Ammonia-oxidizing archaea (AOA), as opposed to ammonia-oxidizing bacteria (AOB), were recently identified as the dominant ammonia oxidizers in most freshwater aquaria. This study investigated biofilms from fixed-bed aquarium biofilters to assess the temporal and spatial dynamics of AOA and AOB abundance and diversity. Over a period of four months, ammonia-oxidizing microorganisms from six freshwater and one marine aquarium were investigated at 4–5 time points. Nitrogen balances for three freshwater aquaria showed that active nitrification by aquarium biofilters accounted for ≥81–86% of total nitrogen conversion in the aquaria. Quantitative PCR (qPCR) for bacterial and thaumarchaeal ammonia monooxygenase (amoA) genes demonstrated that AOA were numerically dominant over AOB in all six freshwater aquaria tested, and contributed all detectable amoA genes in three aquarium biofilters. In the marine aquarium, however, AOB outnumbered AOA by three to five orders of magnitude based on amoA gene abundances. A comparison of AOA abundance in three carrier materials (fine sponge, rough sponge and sintered glass or ceramic rings) of two three-media freshwater biofilters revealed preferential growth of AOA on fine sponge. Denaturing gel gradient electrophoresis (DGGE) of thaumarchaeal 16S rRNA genes indicated that community composition within a given biofilter was stable across media types. In addition, DGGE of all aquarium biofilters revealed low AOA diversity, with few bands, which were stable over time. Nonmetric multidimensional scaling (NMDS) based on denaturing gradient gel electrophoresis (DGGE) fingerprints of thaumarchaeal 16S rRNA genes placed freshwater and marine aquaria communities in separate clusters. These results indicate that AOA are the dominant ammonia-oxidizing microorganisms in freshwater aquarium biofilters, and that AOA community composition within a given aquarium is stable over time and across biofilter support material types.

Abundance and composition of indigenous bacterial communities in a multi-step biofiltration-based drinking water treatment plant

Indigenous bacterial communities are essential for biofiltration processes in drinking water treatment systems. In this study, we examined the microbial community composition and abundance of three different biofilter types (rapid sand, granular activated carbon, and slow sand filters) and their respective effluents in a full-scale, multi-step treatment plant (Zürich, CH). Detailed analysis of organic carbon degradation underpinned biodegradation as the primary function of the biofilter biomass. The biomass was present in concentrations ranging between 2-5 × 10(15) cells/m(3) in all filters but was phylogenetically, enzymatically and metabolically diverse. Based on 16S rRNA gene-based 454 pyrosequencing analysis for microbial community composition, similar microbial taxa (predominantly Proteobacteria, Planctomycetes, Acidobacteria, Bacteriodetes, Nitrospira and Chloroflexi) were present in all biofilters and in their respective effluents, but the ratio of microbial taxa was different in each filter type. This change was also reflected in the cluster analysis, which revealed a change of 50-60% in microbial community composition between the different filter types. This study documents the direct influence of the filter biomass on the microbial community composition of the final drinking water, particularly when the water is distributed without post-disinfection. The results provide new insights on the complexity of indigenous bacteria colonizing drinking water systems, especially in different biofilters of a multi-step treatment plant.

Microbial community response to chlorine conversion in a chloraminated drinking water distribution system

Temporary conversion to chlorine (i.e., "chlorine burn") is a common approach to controlling nitrification in chloraminated drinking water distribution systems, yet its effectiveness and mode(s) of action are not fully understood. This study characterized occurrence of nitrifying populations before, during and after a chlorine burn at 46 sites in a chloraminated distribution system with varying pipe materials and levels of observed nitrification. Quantitative polymerase chain reaction analysis of gene markers present in nitrifying populations indicated higher frequency of detection of ammonia oxidizing bacteria (AOB) (72% of samples) relative to ammonia oxidizing archaea (AOA) (28% of samples). Nitrospira nitrite oxidizing bacteria (NOB) were detected at 45% of samples, while presence of Nitrobacter NOB could not be confirmed at any of the samples. During the chlorine burn, the numbers of AOA, AOB, and Nitrospira greatly reduced (i.e., 0.8-2.4 log). However, rapid and continued regrowth of AOB and Nitrospira were observed along with nitrite production in the bulk water within four months after the chlorine burn, and nitrification outbreaks appeared to worsen 6-12 months later, even after adopting a twice annual burn program. Although high throughput sequencing of 16S rRNA genes revealed a distinct community shift and higher diversity index during the chlorine burn, it steadily returned towards a condition more similar to pre-burn than burn stage. Significant factors associated with nitrifier and microbial community composition included water age and sampling location type, but not pipe material. Overall, these results indicate that there is limited long-term effect of chlorine burns on nitrifying populations and the broader microbial community.

Biofilm community dynamics in bench-scale annular reactors simulating arrestment of chloraminated drinking water nitrification

Annular reactors (ARs) were used to study biofilm community succession and provide ecological insight during nitrification arrestment through simultaneously increasing monochloramine (NH2Cl) and chlorine to nitrogen mass ratios, resulting in four operational periods (I-IV). Analysis of 16S rRNA-encoding gene sequence reads (454-pyrosequencing) examined viable and total biofilm communities and found total samples were representative of the underlying viable community. Bacterial community structure showed dynamic changes corresponding with AR operational parameters. Period I (complete nitrification and no NH2Cl residual) was dominated by Bradyrhizobium (total cumulative distribution: 38%), while environmental Legionella-like phylotypes peaked (19%) during Period II (complete nitrification and minimal NH2Cl residual). Nitrospira moscoviensis (nitrite-oxidizing bacteria) was detected in early periods (2%) but decreased to <0.02% in later periods, corresponding to nitrite accumulation. Methylobacterium (19%) and members of Nitrosomonadaceae (42%) dominated Period III (complete ammonia and partial nitrite oxidation and low NH2Cl residual). An increase in Afipia (haloacetic acid-degrading bacteria) relative abundance (<2% to 42%) occurred during Period IV (minimal nitrification and moderate to high NH2Cl residual). Microbial community and operational data provided no evidence of taxa-time relationship, but rapid community transitions indicated that the system had experienced ecological regime shifts to alternative stable states.

Effects of ultrasonic pretreatment on quantity and composition of bacterial DNA recovered from granular activated carbon used for drinking water treatment

Effects of ultrasonic pretreatment on bacterial DNA recovery from granular activated carbon (GAC) were investigated. GAC (Calgon F400), biologically activated, was sampled from an actual drinking water plant. Different ultrasonic energy densities (0-400 J·cm(-3)) were applied with agitation (250 rpm for 30 min), and recovered bacterial DNA was quantified using quantitative PCR. Energy density was linearly correlated with the concentration of carbon fines produced from GAC during ultrasonication. Ultrasonication alone had no effect on DNA recovery at ≤60 J·cm(-3), but a strongly adverse effect at >67 J·cm(-3) due to the produced carbon fines. Agitation along with ultrasonication strongly enhanced the bacterial DNA recovery when ≤40 J·cm(-3) was applied, although it did not affect the production of carbon fines. Ribosomal tag pyrosequencing was used to compare recovered bacterial communities (0, 20 and 30 J·cm(-3) with or without agitation). Ultrasonication allowed for obtaining a more diverse and richer bacterial community from GAC, compared with the control. Agitation did not show a positive effect on community organization (richness and diversity). Consistently, canonical correspondence analysis indicated that the energy density was associated with the relative abundances of particular bacterial members (P < 0.05), while agitation did not. Correspondence analysis revealed that the recovered bacterial communities were grouped according to the applied energy densities. In conclusion, ultrasonication and agitation influence the recovered DNA in quality and quantity, respectively, and carbon fines as a by-product by ultrasonication interfere with the DNA recovery.

Evaluation of autotrophic growth of ammonia-oxidizers associated with granular activated carbon used for drinking water purification by DNA-stable isotope probing

Nitrification is an important biological function of granular activated carbon (GAC) used in advanced drinking water purification processes. Newly discovered ammonia-oxidizing archaea (AOA) have challenged the traditional understanding of ammonia oxidation, which considered ammonia-oxidizing bacteria (AOB) as the sole ammonia-oxidizers. Previous studies demonstrated the predominance of AOA on GAC, but the contributions of AOA and AOB to ammonia oxidation remain unclear. In the present study, DNA-stable isotope probing (DNA-SIP) was used to investigate the autotrophic growth of AOA and AOB associated with GAC at two different ammonium concentrations (0.14 mg N/L and 1.4 mg N/L). GAC samples collected from three full-scale drinking water purification plants in Tokyo, Japan, had different abundance of AOA and AOB. These samples were fed continuously with ammonium and (13)C-bicarbonate for 14 days. The DNA-SIP analysis demonstrated that only AOA assimilated (13)C-bicarbonate at low ammonium concentration, whereas AOA and AOB exhibited autotrophic growth at high ammonium concentration. This indicates that a lower ammonium concentration is preferable for AOA growth. Since AOA could not grow without ammonium, their autotrophic growth was coupled with ammonia oxidation. Overall, our results point towards an important role of AOA in nitrification in GAC filters treating low concentration of ammonium.

Abundance and community structure of ammonia-oxidizing microorganisms in reservoir sediment and adjacent soils

Ammonia oxidation is an important process for global nitrogen cycling. Both ammonia-oxidizing bacteria (AOB) and archaea (AOA) can be the important players in nitrification process. However, their relative contribution to nitrification remains controversial. This study investigated the abundance and community structure of AOA and AOB in sediment of Miyun Reservoir and adjacent soils. Quantitative PCR assays indicated that the highest AOA abundance occurred in unplanted riparian soil, followed by reservoir sediment, reed-planted riparian soil and agricultural soil. The AOB community size in agricultural soil was much larger than that in the other habitats. Large variations in the structures of AOA and AOB were also observed among the different habitats. The abundance of Nitrosospira-like AOB species were detected in the agricultural soil and reservoir sediment. Pearson's correlation analysis showed the AOB diversity had positive significant correlations with pH and total nitrogen, while the AOA diversity might be negatively affected by nitrate nitrogen and ammonia nitrogen. This work could add new insights towards nitrification in aquatic and terrestrial ecosystems.

Integrated metagenomic and physiochemical analyses to evaluate the potential role of microbes in the sand filter of a drinking water treatment system

While sand filters are widely used to treat drinking water, the role of sand filter associated microorganisms in water purification has not been extensively studied. In the current investigation, we integrated molecular (based on metagenomic) and physicochemical analyses to elucidate microbial community composition and function in a common sand filter used to treat groundwater for potable consumption. The results revealed that the biofilm developed rapidly within 2 days (reaching ∼10¹¹ prokaryotes per gram) in the sand filter along with abiotic and biotic particulates accumulated in the interstitial spaces. Bacteria (up to 90%) dominated the biofilm microbial community, with Alphaproteobacteria being the most common class. Thaumarchaeota was the sole phylum of Archaea, which might be involved in ammonia oxidation. Function annotation of metagenomic datasets revealed a number of aromatic degradation pathway genes, such as aromatic oxygenase and dehydrogenase genes, in the biofilm, suggesting a significant role for microbes in the breakdown of aromatic compounds in groundwater. Simultaneous nitrification and denitrification pathways were confirmed as the primary routes of nitrogen removal. Dissolved heavy metals in groundwater, e.g. Mn²⁺ and As³⁺, might be biologically oxidized to insoluble or easily adsorbed compounds and deposited in the sand filter. Our study demonstrated that the role of the microbial community in the sand filter treatment system are critical to effective water purification in drinking water.

Effective microbes for simultaneous bio-oxidation of ammonia and manganese in biological aerated filter system

This study determined the most effective microbes acting as ammonia-oxidising (AOB) and manganese-oxidising bacteria (MnOB) for the simultaneous removal of ammonia (NH(4)(+)-N) and manganese (Mn(2+)) from water. Two conditions of mixed culture of bacteria: an acclimatised mixed culture (mixed culture: MC) in a 5-L bioreactor and biofilm attached on a plastic medium (stages of mixed culture: SMC) in a biological aerated filter were isolated and identified using Biolog MicroSystem and 16S rRNA sequencing. A screening test for determining the most effective microbe in the removal of NH(4)(+)-N and Mn(2+) was initially performed using SMC and MC, respectively, and found that Bacillus cereus was the most effective microbe for the removal of NH(4)(+)-N and Mn(2+). Moreover, the simultaneous NH(4)(+)-N and Mn(2+) removal (above 95% removal for both NH(4)(+)-N and Mn(2+)) was achieved using a biological aerated filter under various operating conditions. Thus, the strain could act as an effective microbe of AOB and a MnOB for the simultaneous removal of NH(4)(+)-N and Mn(2+).

Low-ammonia niche of ammonia-oxidizing archaea in rotating biological contactors of a municipal wastewater treatment plant

The first step of nitrification is catalysed by both ammonia-oxidizing bacteria (AOB) and archaea (AOA), but physicochemical controls on the relative abundance and function of these two groups are not yet fully understood, especially in freshwater environments. This study investigated ammonia-oxidizing populations in nitrifying rotating biological contactors (RBCs) from a municipal wastewater treatment plant. Individual RBC stages are arranged in series, with nitrification at each stage creating an ammonia gradient along the flowpath. This RBC system provides a valuable experimental system for testing the hypothesis that ammonia concentration determines the relative abundance of AOA and AOB. The results demonstrate that AOA increased as ammonium decreased across the RBC flowpath, as indicated by qPCR for thaumarchaeal amoA and 16S rRNA genes, and core lipid (CL) and intact polar lipid (IPL) crenarchaeol abundances. Overall, there was a negative logarithmic relationship (R² = 0.51) between ammonium concentration and the relative abundance of AOA amoA genes. A single AOA population was detected in the RBC biofilms; this phylotype shared low amoA and 16S rRNA gene homology with existing AOA cultures and enrichments. These results provide evidence that ammonia availability influences the relative abundances of AOA and AOB, and that AOA are abundant in some municipal wastewater treatment systems.

Archaeal amoA genes outnumber bacterial amoA genes in municipal wastewater treatment plants in Bangkok

The contribution of ammonia-oxidizing archaea (AOA) to nitrogen removal in wastewater treatment plants (WWTPs) remains unknown. This study investigated the abundance of archaeal (AOA) and bacterial (ammonia-oxidizing bacteria (AOB)) amoA genes in eight of Bangkok's municipal WWTPs. AOA amoA genes (3.28 × 10(7) ± 1.74 × 10(7)-2.23 × 10(11) ± 1.92 × 10(11) copies l(-1) sludge) outnumbered AOB amoA genes in most of the WWTPs even though the plants' treatment processes, influent and effluent characteristics, removal efficiencies, and operation varied. An estimation of the ammonia-oxidizing activity of AOA and AOB suggests that AOA involved in autotrophic ammonia oxidation in the WWTPs. Statistical analysis shows that the numbers of AOA amoA genes correlated negatively to the ammonium levels in effluent wastewater, while no correlation was found between the AOA amoA gene numbers and the oxygen concentrations in aeration tanks. An analysis of the AOB sequences shows that AOB found in the WWTPs limited to only two AOB clusters which exhibit high or moderate affinity to ammonia. In contrast to AOB, AOA sequences of various clusters were retrieved, and they were previously recovered from a variety of environments, such as thermal and marine environments.

Abundance of amoA genes of ammonia-oxidizing archaea and bacteria in activated sludge of full-scale wastewater treatment plants

In this study, the abundance and sequences of amoA genes of ammonia-oxidizing archaea (AOA) and bacteria (AOB) were determined in seven wastewater treatment plants (WWTPs) whose ammonium concentrations in influent and effluent wastewaters varied considerably (5.6-422.3 mgN l(-1) and 0.2-29.2 mgN l(-1), respectively). Quantitative real-time PCR showed that the comparative abundance of AOA and AOB amoA genes differed among the WWTPs. In all three industrial WWTPs, where the influent and effluent contained the higher levels of ammonium (36.1-422.3 mgN l(-1) and 5.3-29.2 mgN l(-1), respectively), more than four orders of magnitude higher numbers of AOB amoA genes than AOA amoA genes arose (with less than the limit of detection of AOA amoA genes). In contrast, significant numbers of AOA amoA genes occurred in all municipal WWTPs (with ammonium levels in the influent and effluent of 5.6-11.0 mgN l(-1) and 0.2-3.0 mgN l(-1), respectively). Statistical analysis suggested that compared to other plants' parameters, the ammonium levels in the plants' effluent showed correlation with the highest p value to the abundance of AOA amoA genes.

Ammonia-oxidizing bacteria in biofilters removing trihalomethanes are related to Nitrosomonas oligotropha

Ammonia-oxidizing bacteria (AOB) in nitrifying biofilters degrading four regulated trihalomethanes-trichloromethane, bromodichloromethane, dibromochloromethane, and tribromomethane-were related to Nitrosomonas oligotropha. N. oligotropha is associated with chloraminated drinking water systems, and its presence in the biofilters might indicate that trihalomethane tolerance is another reason that this bacterium is dominant in chloraminated systems.