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 <i>Bradyrhizobium</i> (total cumulative distribution: 38%), while environmental <i>Legionella</i>-like phylotypes peaked (19%) during Period II (complete nitrification and minimal NH₂Cl residual). <i>Nitrospira moscoviensis</i> (nitrite-oxidizing bacteria) was detected in early periods (2%) but decreased to <0.02% in later periods, corresponding to nitrite accumulation. <i>Methylobacterium</i> (19%) and members of <i>Nitrosomonadaceae</i> (42%) dominated Period III (complete ammonia and partial nitrite oxidation and low NH₂Cl residual). An increase in <i>Afipia</i> (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

The Impact of Silver Nanoparticles on the Composting of Municipal Solid Waste

The study evaluates the impact of polyvinylpyrrolidone (PVP) coated silver nanoparticles (PVP-AgNPs) on the composting of municipal solid waste. The results suggest that there was no statistically significant difference in the leachate, gas, and solid quality parameters and overall composting performance between the treatments containing the AgNPs, Ag⁺, and negative control. Nonetheless, taxonomical analyses of 25 Illumina 16S rDNA barcoded libraries containing 2 393 504 sequences indicated that the bacterial communities in composted samples were highly diverse and primarily dominated by Clostridia (48.5%), Bacilli (27.9%), and beta-Proteobacteria (13.4%). Bacterial diversity studies showed that the overall bacterial community structure in the composters changed in response to the Ag-based treatments. However, the data suggest that functional performance was not significantly affected due to potential bacterial functional redundancy within the compost samples. The data also indicate that while the surface transformation of AgNPs to AgCl and Ag₂S can reduce the toxicity, complexation with organic matter may also play a major role. The results of this study further suggest that at relatively low concentrations, the organically rich waste management systems’ functionality may not be influenced by the presence of AgNPs

Categorized distance and proportion of cases within those groups in a waterborne outbreak in Vuorela, July 2012.

<p>Categorized distance and proportion of cases within those groups in a waterborne outbreak in Vuorela, July 2012.</p

The Univariate and multivariate results for individual risk factors and the generalized additive model risk ratios with the spatial term of a waterborne outbreak in Vuorela, July 2012.

<p>The Univariate and multivariate results for individual risk factors and the generalized additive model risk ratios with the spatial term of a waterborne outbreak in Vuorela, July 2012.</p

Epidemic curve of a waterborne outbreak in Vuorela, July 2012 based on the reported onset date of illness of the cases, and <i>E. coli</i> bacteria counts and chlorine levels in the point 7 (See Fig. 1) of the water distribution network.

<p>Epidemic curve of a waterborne outbreak in Vuorela, July 2012 based on the reported onset date of illness of the cases, and <i>E. coli</i> bacteria counts and chlorine levels in the point 7 (See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104713#pone-0104713-g001" target="_blank">Fig. 1</a>) of the water distribution network.</p

Microbiological results of faecal samples from symptomatic patients of a waterborne outbreak in Vuorela, July 2012.

<p>Methods used were cultivation¹, PCR/RT-PCR² (polymerase chain reaction/reverse transcripition-PCR), EM³ (electron microscopy) and/or EIA⁴ (Enzyme Immunoassay). ⁵<i>Campylobacter jejuni</i> and ⁶EHEC O157:H7 (from one sample) and ⁷sapovirus GII.P3 were isolated from the samples.</p

Phylogenetic relationships among OTUs (•) of the genus <i>Arcobacter</i> in a waterborne outbreak in Vuorela, July 2012.

<p>The tree was inferred from a maximum likelihood analysis of aligned 16S rRNA gene sequence (≈255 bp) and nodes with a bootstrap value ≥50% of 1 000 replicates are identified. <i>Sulfurospirillum deleyianum</i> (NR_074378) and <i>Campylobacter fetus</i> (L04314) were used as outgroup. Number in bracket represents the total amount of DNA/RNA reads identified in samples from A) the upper storage reservoir before cleaning, B) tap water during contamination and C) the upper storage reservoir after cleaning. *<i>A. butzleri</i>, <i>A. cryaerophilus</i> and <i>A. skirrowii</i> have been associated with gastrointestinal diseases <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104713#pone.0104713-Collado1" target="_blank">[76]</a>.</p