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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. [ABSTRACT FROM AUTHOR]

The presence of pathogenic viruses in drinking water is a major public health concern. Although viability RT-qPCR methods were developed to quantify infectious viruses, they may not always reflect viral infectivity, therefore leading to false-positive results. In this study, sodium deoxycholate (SD) pre-treatment was used to improve the efficiency of viability RT-qPCR methods with respect to exclusive quantification of infectious viruses. The ability of SD pre-treatment to enhance the penetration of three viability markers, namely, ethidium monoazide (EMA, 100 µM), propidium monoazide (PMA, 100 µM), and cis-dichlorodiammineplatinum (CDDP, 1000 µM), into heat-treated (90 °C for 1 min) Aichi virus at various concentrations (0.01-0.5%) was evaluated. The optimal SD concentration was found to be 0.1% for all markers. EMA/PMA/CDDP-RT-qPCR with 0.1% SD pre-treatment was significantly more effective than without SD pre-treatment in determining AiV inactivation after heat (50, 60, 70, 80, or 90 °C for 1 min) or chlorine treatment (1 mgCl2/L for 1, 2, 5, or 10 min). Among the viability RT-qPCR methods tested, CDDP-RT-qPCR with SD pre-treatment (SD-CDDP-RT-qPCR) was the most effective in reflecting viral infectivity. Performance testing of SD-CDDP-RT-qPCR in concentrated drinking water samples did not reveal any significant effects of SD-CDDP treatment. Thus, SD-CDDP-RT-qPCR could be a useful tool for monitoring infectious virus presence in drinking water. [ABSTRACT FROM AUTHOR]

Abstract: Ultraviolet light emitting diodes (UV‐LEDs) are small mercury‐free devices that can be installed at the point of use (POU) of water for disinfection. Considering that heterotrophic bacteria are of concern in drinking water systems, we applied a flow‐through UV‐LED apparatus to dechlorinated tap water, and determined the heterotrophic plate count (HPC) in samples after UV‐LED exposure (UV+) compared to samples without UV‐LED application (UV−). The UV+ and UV− samples were maintained at 20°C to track HPC profiles during storage for 7 days. It was confirmed that UV+ samples showed negative HPC or lower HPC than UV− for 5 days of storage after the flow‐through test. HPC bacteria formed colonies with different morphological characteristics, and yellow colonies were closest to Novosphingobium sp., with 99% identity, while white and pale pink colonies were closest to Methylobacterium sp., with 99–100% identity, based on 16S rRNA gene sequences. White colonies became dominant in UV+, indicating that UV‐LED exposure can select UV‐resistant species such as Methylobacterium. This study shows the effects of UV‐LED application on HPC bacteria in tap water and implies that future research is required on the significance and impacts of microbial selection by UV‐LED exposure. [ABSTRACT FROM AUTHOR]

Ammonia is a precursor to trichloramine, which causes an undesirable chlorinous odor. Granular activated carbon (GAC) filtration is used to biologically oxidize ammonia during drinking water purification; however, little information is available regarding the abundance and diversity of ammonia-oxidizing archaea (AOA) and bacteria (AOB) associated with GAC. In addition, their sources and fates in water purification process remain unknown. In this study, six GAC samples were collected from five full-scale drinking water purification plants in Tokyo during summer and winter, and the abundance and community structure of AOA and AOB associated with GAC were studied in these two seasons. In summer, archaeal and bacterial amoA genes on GACs were present at 3.7 × 10-3.9 × 10 gene copies/g-dry and 4.5 × 10-4.2 × 10 gene copies/g-dry, respectively. In winter, archaeal amoA genes remained at the same level, while bacterial amoA genes decreased significantly for all GACs. No differences were observed in the community diversity of AOA and AOB from summer to winter. Phylogenetic analysis revealed high AOA diversity in group I.1a and group I.1b in raw water. Terminal-restriction fragment length polymorphism analysis of processed water samples revealed that AOA diversity decreased dramatically to only two OTUs in group I.1a after ozonation, which were identical to those detected on GAC. It suggests that ozonation plays an important role in determining AOA diversity on GAC. Further study on the cell-specific activity of AOA and AOB is necessary to understand their contributions to in situ nitrification performance. [ABSTRACT FROM AUTHOR]

The benthic ostracod Heterocypris incongruens is becoming an important tool for the ecotoxicological assessment of contaminated sediments. However, no study has yet explored solid-phase (dietary) exposure to ostracod. The present study examined the effects of metals on H. incongruens through aquatic and dietary exposures. The algal food Chlorella vulgaris was exposed to different concentrations of cadmium (Cd), copper (Cu), and zinc (Zn), and subcellular distributions of these metals in algal cells were determined. Parallel experiments were also performed to determine the toxic effects of dissolved metals on ostracod through aqueous exposure. Significant toxic effects on mortality were observed when ostracod were fed with Cd-contaminated (47-100%) and Cu-contaminated algae (55-100%). With increasing accumulated Zn in the algal cell, ostracod mortality also increased (20-83%). Aquatic exposure of ostracod to different concentrations of dissolved Cd (3.2-339 µg Cd/L) and Cu (260-2600 µg Cu/L) resulted in high observed mortalities (57-100% and 95-100%, respectively). Based on the results of aqueous and dietary exposure tests, it can be concluded that both exposure routes are important in evaluating the toxic effect of Cd on ostracod. Similar results were observed in tests using other metals (i.e., using Cu and Zn), thus emphasizing the importance of considering not only aquatic but also dietary exposure routes when evaluating metal toxicity to ostracod. Environ Toxicol Chem 2014;33:1624-1630. © 2014 SETAC [ABSTRACT FROM AUTHOR]

Microbial regrowth causes problems during water reuse. Comprehensive understanding of the microorganisms that can regrow in reclaimed water and their substrate requirements are necessary. In this study, potential regrowth organisms were isolated from seven water reclamation plants in Japan. Based on 16S rDNA analysis, the isolates were grouped into 34 operational taxonomic units, belonging to Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes. Substrate utilization profiling using Biolog microplate™ classified the isolates into four groups. Bacteria in Cluster 1 (e.g., Methylobacterium sp. and Acinetobacter sp.) mainly utilized polymers, esters, amides, and alcohol. Isolates in Cluster 2 (e.g., Flavobacterium sp. and Microbacterium sp.) preferred to utilize polymers, carbohydrates, and esters. Isolates in Cluster 3 (e.g., Pseudomonas sp. and Acidovorax sp.) mainly utilized esters, carboxylic acids, and amino acids. Isolates in Cluster 4 (e.g., Enterobacter sp. and Rhodococcus sp.) utilized carbohydrates, esters, and amino acids. All isolates grew in reclaimed water treated by sand filtration, whereas some isolates could not grow in reclaimed water treated by coagulation and ozonation. Most bacteria in the same Biolog clusters exhibited similar growth characteristics in water samples. The potential of bacteria to regrow in reclaimed water likely depended on substrate requirement. [ABSTRACT FROM AUTHOR]

The use of randomly generated DNA fragment sequences as probes on DNA arrays offers a unique potential for exploring unsequenced microorganisms. In this study, the detection specificity was evaluated with respect to probe-target sequence similarity using genomic DNAs of four Pseudomonas strains. Genome fragments averaging 2000 bp were found to be specific enough to discriminate 85-90% similarity under highly stringent hybridization conditions. Such stringent conditions compromised signal intensities; however, specific signals remained detectable at the highest stringency (at 75 °C hybridization) with negligible false negatives. These results suggest that, without any probe design or selection, genomic fragments can provide a reasonable specificity for microbial diagnostics or species delineation by DNA- DNA similarities. [ABSTRACT FROM AUTHOR]

This study was aimed at comparing the Zn and Cu binding parameters with dissolved organic matter (DOM) in road runoff, wastewater treatment plant (WWTP) effluent and influent. Conditional stability constant (K') and binding site concentration ([L]) are important to predict free or labile metal concentration and toxicity in the water environment. The values of K' and [L] of three DOMs were determined by metal titration and Scatchard linearization. The Zn and Cu titration data for DOMs in WWTP effluent and influent fitted to a two-ligand model, while DOM in road runoff fitted to a single-ligand model. The order of the values of K' was WWTP influent > WWTP effluent > road runoff both for Zn and Cu. Total ambient binding site concentration ([LT]) was lower in DOM of road runoff (1.4-1.5μM) than those in DOM of WWTP effluent (1.6-2.3μM) and influent (17-18μM), suggesting lower metal complexation capacity in DOM of road runoff. DOM in WWTP influent was expected to bind to both Zn and Cu more strongly than that of the effluent DOM. [ABSTRACT FROM AUTHOR]

Selective sequential dissolution (SSD) and isotopic dilution are two most commonly applied techniques for the measurement of mobile fraction of heavy metal present in the urban environment. This work examined the compliance between SSD proposed by the Community Bureau of Reference (BCR) and isotopic dilution technique (IDT) for determination of mobile pool of heavy metal contained in soakaway sediment, road dust, and soil sample. Heavy metals (Cu, Zn, Cd and Pb) were fractionated using the three-stage BCR protocol, while isotopically exchangeable metal concentrations (E-value) were investigated through isotopic tracers (111Cd, 65Cu, 207Pb and 66Zn). In general, total contamination level, E-value and BCR exchangeable fractions of different samples followed the similar order of road dust . soakaway sediment . soil. Results revealed that the E-value exceeded the BCR exchangeable fraction in all samples. In addition, the first three fractions of BCR which have potential to become mobile under certain environmental conditions were collectively termed as "potential mobile pool" and compared with E-value. It was concluded that metal extracted by weak acid underestimates the exchangeable fraction while the potential mobile pool extracted by three reagents overestimates the real mobile forms of heavy metals. However, better mobility characteristics of heavy metals can be assessed by coupling information obtained through sequential extraction and isotopic exchange. [ABSTRACT FROM AUTHOR]

The effects of different placements of rapid sand filtration on nitrification performance of BAC treatment in a pilot-scale plant were evaluated. In this plant, rapid sand filtration was placed after ozonation-BAC treatment in Process (A), while it preceded ozonation-BAC treatment in Process (B). Analysis of amoA genes of ammonia-oxidizing archaea (AOA) and bacteria (AOB) combined with nitrification potential test was conducted. BAC from Process (A) demonstrated slightly higher nitrification potential at every sampling occasion. This might be due to higher abundances of AOB on BAC from Process (A) than those on BAC from Process (B). However, AOA rather than AOB could be predominant ammonia-oxidizers in BAC treatment regardless of the position of rapid sand filtration. The highest nitrification potential was observed for BAC from both processes in February when the highest abundances of AOA-amoA and AOB-amoA genes were detected. Since rapid sand filtration was placed after BAC treatment in Process (A), residual aluminum concentration in BAC influent was higher in Process (A). However, adverse effects of aluminum on nitrification activity were not observed. These results suggest that factors other than aluminum concentration in different treatment processes could possibly have some influence on abundances of ammonia-oxidizing microorganisms on BAC. [ABSTRACT FROM AUTHOR]

Lead (Pb) isotopic data were used in this study to first distinguish the partitioning of anthropogenic and natural lead in different fractions, obtained by BCR sequential extraction, and then to anticipate their mixing process in the soakaway sediment of artificial infiltration facilities (AIF). Total metal content was found higher in soakaway sediment samples than that of soil. The lowest 206Pb/207Pb ratios were mostly observed in exchangeable fractions of soil and sediment samples, while residual fractions mostly showed the highest 206Pb/207Pb and 208Pb/207Pb ratios than those of other fractions. In general, both ratios were higher in the soil than those of sediments. Further among soil samples, residual fraction of bottom soil exhibited higher ratios than surface soil indicating higher contribution of natural lead with depth. In addition, the difference in Pb content, partitioning and its isotope signature among four sediment samples were also investigated considering their sampling locations. The plot of 206Pb/207Pb versus 208Pb/207Pb showed two well demarcated cluster formations by soil and sediments samples that describe the partitioning between anthropogenic and natural lead; and some points falling in between soil and sediment samples pertinently illustrated the mixing processes between these two different pools of lead. [ABSTRACT FROM AUTHOR]

Diverse environmental genes have been identified recently. To characterize their functions, it is necessary to understand which genes and what combinations of those genes are responsible for the biodegradation of soil contaminants. In this article, a 60-mer oligonucleotide microarray was constructed to simultaneously detect di- and monooxygenase genes for benzene and related compounds. In total, 148 probes were designed and validated by pure-culture hybridizations using the following criteria to discriminate between highly homologous genes: ≤53-bp identities and ≤25-bp continuous stretch to nontarget sequences. Microarray hybridizations were performed using PCR products amplified from five benzene-amended soils and two oil-contaminated soils. Six of the probes gave a positive signal for more than six soils; thus, they may represent key sequences for benzene degradation in the environment. The microarray developed in this study will be a powerful tool for the screening of key genes involved in benzene degradation and for the rapid profiling of benzene oxygenase gene diversity in contaminated soils. [ABSTRACT FROM AUTHOR]

Catechol 2,3-dioxygenase (C23O) is an extradiol dioxygenase that plays an important role in degrading aromatic compounds such as those found at polluted sites. However, little is known about the diversity of C23O genes in unpolluted environments. In such environments, various factors, including the quality and quantity of dissolved organic matter (DOM), could influence the composition and behaviour of bacterial community possessing C230 genes. We investigated C23O genes in bacteria responding to DOM from various sources in a eutrophic lake by PCR and cloning. Six microcosms filled with lake water containing indigenous bacteria and DOM from different sources were incubated for 10 days. After 1 or 2 days of incubation, C23O genes were detected in the microcosms enriched with DOM recovered from inflow river water and humus from reed grass. The sequences were very diverse but had features conserved in extradiol dioxygenases. The clone libraries generated on day 2 showed distinctive compositions among microcosms, indicating that bacteria possessing a variety of C23O genes responded differently to DOM from different sources. After 10 days of incubation, C23O genes in a previously unidentified gene cluster, ‘Cluster X’, became dominant in the libraries. [ABSTRACT FROM AUTHOR]

This study is aimed to investigate biological oxidation of arsenic [As(III)] in sand component of arsenic–iron removal plant (AIRP). Water and sand samples were collected from the municipal and household AIRP units (MAIRP and HAIRPs) at Manikganj district, Bangladesh. These samples were analyzed using arsenic speciation cartridge with inductively coupled plasma-mass spectrometry for arsenic and iron detection and phylogenetic analysis based on aoxB gene sequencing. It was observed that arsenic concentration in the raw water, before and after sand filtration, ranged from 13.0–81.0 to 4.0–21.0 μg/L, respectively, which majorly contained reduced arsenic [As(III)] in the inlet and oxidized arsenic [As(V)] in the outlet. The results of our batch experiments showed that indeed sand unit of MAIRP oxidized As(III) with 36 g/h estimated biological oxidation potential which was considered enough to oxidize all the As(III) loading (6.3 g/h) in the influent. Additionally, bacterial arsenite oxidase gene (aoxB) was detected in the sand sample and has 80% sequence similarity with Polymorphum gilvum, an alphaproteobacteria on the phylogenetic tree. This study, therefore, revealed that AIRP sand units have enough potential of biological activity to ensure overall arsenic removal through As(III) oxidation. However, future research is necessary to unfold the basic mechanistic approach explored in this plant for further modification if need arises. [ABSTRACT FROM AUTHOR]

Granular activated carbon (GAC) has been widely introduced to advanced drinking water purification plants to remove organic matter and ammonium. Backwashing, which is the routine practice for GAC maintenance, is an important operational factor influencing the performance of GAC and its microbial biomass. In this study, the effects of backwashing on the ammonium removal potential of GAC were evaluated. In addition, abundances of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) on GAC were analyzed. GAC samples before and after backwashing were collected from a full-scale drinking water purification plant. Samplings were conducted before and after implementation of prechlorination of raw water. The results showed that the ammonium removal potential of the GAC increased by 12% after backwashing before prechlorination (p < 0.01). After implementing the prechlorination, the ammonium removal potential of the GAC decreased by 12% even after backwashing (p < 0.01). The AOA was predominant on the GAC in the two samplings. Regardless of prechlorination, the amounts of the AOA and the AOB remained at the same level before and after backwashing. Analysis of the backwashing water indicated that the amounts of the AOA and AOB washed out from the GAC were negligible (0.08%–0.26%) compared with their original amounts on the GAC. These results revealed the marginal role of backwashing on the biomass of ammonia oxidizers on GAC. However, the results also revealed that backwashing could have a negative impact on the ammonium removal potential of GAC during prechlorination. [ABSTRACT FROM AUTHOR]