Impact of Chloramination on the Development of Oligotrophic Biofilms

This study aimed to i) determine the effectiveness of monochloramine disinfection on biofilm control and ii) characterize the architecture and community development of laboratory-grown oligotrophic biofilms over a two-month period. Biofilm development and disinfection were realized in Center for Disease Control (CDC) reactor systems with PVC coupons as the substratum and groundwater as the seeding and growth nutrient. To compare biofilm development under disinfection against its natural development, two CDC reactors (treatment and control) were operated. In the treatment reactor, chloramination at 8.5 ± 0.2 mg Cl2/L as combined chlorine was applied after two weeks of biofilm growth till the end of week 10. Confocal laser scanning microscopy combined with quantitative analysis using COMSTAT program revealed that disinfection resulted in a reduction of average thickness and biomass volume by 83.6% and 81.8%, respectively, and an increase in compactness by 76.5%, suggesting the formation of a thin and compact biofilm with low biomass. In contrast, biofilm development in the control reactor led to an increase in average thickness and biomass volume by a factor of 5.2 and 47.1%, and a reduction in compactness by 75.5%. As the result, thicker and fluffier biofilm architecture was observed. Biofilm community structure change was revealed by cluster analysis and non-metric multidimensional scaling based on 16S rRNA gene-based microbial fingerprinting analysis. Samples from different reactors at the same time point had a high similarity before disinfection, but became dissimilar after disinfection. This suggested that disinfection could lead to the development of a biofilm community with a distinctive community structure. Overall findings suggest that disinfection could influence the growth of multi-species biofilms on PVC surface, shape the biofilm architecture, and select a microbial community thatcan survive, adapt, or proliferate under chloramination. These findings are important to better understand biofilm growth in chloraminated drinking water distribution systems

Understanding the microbiota in drinking water distribution networks – from municipal to indoor water supply systems

A drinking water distribution system can be viewed as an ecosystem that is comprised of diverse microorganisms interacting with each other and the environment. These microorganisms are central to water quality integrity during distribution. This study investigated the diversity, structure, and spatio-temporal variation of microbial communities in the municipal distribution system and indoor plumbing. The Champaign-Urbana water distribution system, which received conventionally treated and disinfected groundwater, was used as a model system. High throughput sequencing (454 pyrosequencing and Illumina Mi-seq sequencing) was used to study the diversity, and flow cytometry was used to quantify microbial abundance. For the municipal distribution system, the study focused on the biofilm component. Microbial communities were sampled from household water meters (n=213). Tap water communities (n=20) were also sampled for comparisons. A positive correlation between OTU abundance and occupancy was observed. Highly abundant and prevalent OTUs were observed and defined as "core populations" in the biofilm and suspended communities. The biofilm core population overlapped with the suspended community and formed a "shared core population," including taxa related to methano-/methylotrophy and aerobic heterotrophy. Despite that, the biofilm community differed from the suspended community by specific core populations and lower diversity and evenness. Multivariate tests indicated seasonality as the main contributor to community structure variation. Indoor plumbing has smaller pipelines and is prone to stagnation, therefore biological growth is expected. However, the magnitude of biological growth and the possible community composition change is not clear. Thus, we examined the impact of stagnation on the community composition in the tap water community. We treated three dormitory buildings in Champaign-Urbana as natural laboratories and conducted a controlled stagnation test. Our results showed that the microbial abundance increased from <103 cells/mL to ~105 cells/mL after a week-long stagnation. The community structure of post-stagnation water significantly differed from the pre-stagnation water. Multivariate analysis showed a significant difference between stagnant and fresh tap water communities. The building, floor, and faucet of sample collection were also shown as significant sources of variation, yet to a lesser degree than stagnation. Temporal variation did not significantly influence the community structure. The post-stagnation communities further exhibited differentiation by flow volumes, which again indicate the influence from the pipeline structure. Methylotrophy and aerobic heterotrophy-related taxa were observed in the post-stagnation communities. Overall, this study has demonstrated that spatiotemporal experiments combined with hypothesis testing can lead to new understanding of drinking water supply systems. Source water community, seasons, and water use (stagnation) were shown to profoundly influence microbial communities in the distribution system. Our findings further showed taxa indicative of a certain carbon source and cell count gradients indicative of stagnation. These findings suggest that the microbiota in the distribution system is a valuable source of information within the distribution system and can be harnessed to complement current monitoring

Global diversity and biogeography of bacterial communities in wastewater treatment plants

Microorganisms in wastewater treatment plants (WWTPs) are essential for water purification to protect public and environmental health. However, the diversity of microorganisms and the factors that control it are poorly understood. Using a systematic global-sampling effort, we analysed the 16S ribosomal RNA gene sequences from ~1,200 activated sludge samples taken from 269 WWTPs in 23 countries on 6 continents. Our analyses revealed that the global activated sludge bacterial communities contain ~1 billion bacterial phylotypes with a Poisson lognormal diversity distribution. Despite this high diversity, activated sludge has a small, global core bacterial community (n = 28 operational taxonomic units) that is strongly linked to activated sludge performance. Meta-analyses with global datasets associate the activated sludge microbiomes most closely to freshwater populations. In contrast to macroorganism diversity, activated sludge bacterial communities show no latitudinal gradient. Furthermore, their spatial turnover is scale-dependent and appears to be largely driven by stochastic processes (dispersal and drift), although deterministic factors (temperature and organic input) are also important. Our findings enhance our mechanistic understanding of the global diversity and biogeography of activated sludge bacterial communities within a theoretical ecology framework and have important implications for microbial ecology and wastewater treatment processes

A flame from water

Bacteria that attach to surfaces can form biofilms, a multi-cellular entity in polymeric matrices produced by cells. Living in biofilms provides benefits such as physical barriers against hostile environments and social opportunities such as exchange of nutrients and coordinated behaviors. In fact, biofilm is the predominant form of bacterial life in many environments. One of such environments is the interior of drinking water networks. Even with the presence of disinfectants, diverse species of bacteria can persist under the shields of biofilm matrix. These bacteria are primarily non-pathogenic, yet they can be problematic under contamination scenarios, when intrusive pathogens can use biofilms as a haven. My research aims to elucidate the diversity of biofilm communities in water distribution networks and seek potentials of using them as a natural monitoring tool for waterborne disease prevention. My picture was taken after bacterial cells sourced from groundwater had formed biofilms and then persisted after months of disinfection. What is it like to sustain life under disinfection? Looking at this picture, one can see that cells, intact (green dots) or damaged (red dots), are embedded in an amorphous matrix (the blue signals) as biofilms. The biofilms are from water, but look like a flame.Ope

Microbial communities as biosensors for monitoring urban environments

The BE microbiome is a naturally embedded biosensor in urban infrastructure that can be used to monitor environmental quality and human activity. There are many potential opportunities for leveraging BE microbial communities to guide urban design and public health policy

A flame from water

Bacteria that attach to surfaces can form biofilms, a multi-cellular entity in polymeric matrices produced by cells. Living in biofilms provides benefits such as physical barriers against hostile environments and social opportunities such as exchange of nutrients and coordinated behaviors. In fact, biofilm is the predominant form of bacterial life in many environments. One of such environments is the interior of drinking water networks. Even with the presence of disinfectants, diverse species of bacteria can persist under the shields of biofilm matrix. These bacteria are primarily non-pathogenic, yet they can be problematic under contamination scenarios, when intrusive pathogens can use biofilms as a haven. My research aims to elucidate the diversity of biofilm communities in water distribution networks and seek potentials of using them as a natural monitoring tool for waterborne disease prevention. My picture was taken after bacterial cells sourced from groundwater had formed biofilms and then persisted after months of disinfection. What is it like to sustain life under disinfection? Looking at this picture, one can see that cells, intact (green dots) or damaged (red dots), are embedded in an amorphous matrix (the blue signals) as biofilms. The biofilms are from water, but look like a flame.Ope

Toward Characterizing Environmental Sources of Non-tuberculous Mycobacteria (NTM) at the Species Level: A Tutorial Review of NTM Phylogeny and Phylogenetic Classification

Nontuberculous mycobacteria (NTM) are any mycobacteria that do not cause tuberculosis or leprosy. While the majority of NTM are harmless and some of them are considered probiotic, a growing number of people are being diagnosed with NTM infections. Therefore, their detection in the environment is of interest to clinicians, environmental microbiologists, and water quality researchers alike. This review provides a tutorial on the foundational approaches for taxonomic classifications, with a focus on the phylogenetic relationships among NTM revealed by the 16S rRNA gene, rpoB gene, and hsp65 gene, and by genome-based approaches. Recent updates on the Mycobacterium genus taxonomy are also provided. A synthesis on the habitats of 189 mycobacterial species in a genome-based taxonomy framework was performed, with attention paid to environmental sources (e.g., drinking water, aquatic environments, and soil). The 16S rRNA gene-based classification accuracy for various regions was evaluated (V3, V3–V4, V3–V5, V4, V4–V5, and V1–V9), revealing overall excellent genus-level classification (up to 100% accuracy) yet only modest performance (up to 63.5% accuracy) at the species level. Future research quantifying NTM species in water systems, determining the effects of water treatment and plumbing conditions on their variations, developing high throughput species-level characterization tools for use in the environment, and incorporating the characterization of functions in a phylogenetic framework will likely fill critical knowledge gaps. We believe this tutorial will be useful for researchers new to the field of molecular or genome-based taxonomic profiling of environmental microbiomes. Experts may also find this review useful in terms of the selected key findings of the past 30 years, recent updates on phylogenomic analyses, as well as a synthesis of the ecology of NTM in a phylogenetic framework

Assessing the transition effects in a drinking water distribution system caused by changing supply water quality: an indirect approach by characterizing suspended solids

Worldwide, it is common that the drinking water distribution systems (DWDSs) may be subjected to changes of supply water quality due to the needs of upgrading the treatment processes or switching the source water. However, the potential impacts of quality changed supply water on the stabilized ecological niches within DWDSs and the associated water quality deterioration risks were poorly documented. In the present study, such transition effects caused by changing the supply water quality that resulted from destabilization of biofilm and loose deposits in DWDS were investigated by analyzing the physiochemical and microbiological characteristics of suspended particles before (T0), during (T3-weeks) and after upgrading the treatments (T6-months) in an unchlorinated DWDS in the Netherlands. Our results demonstrated that after 6 months’ time the upgraded treatments significantly improved the water quality. Remarkably, water quality deterioration was observed at the initial stage when the quality-improved treated water distributed into the network at T3-weeks, observed as a spike of total suspended solids (TSS, 50–260%), active biomass (ATP, 95–230%) and inorganic elements (e.g. Mn, 130–250%). Furthermore, pyrosequencing results revealed sharp differences in microbial community composition and structure for the bacteria associated with suspended particles between T0 and T3-weeks, which re-stabilized after 6 months at T6-months. The successful capture of transition effects was especially confirmed by the domination of Nitrospira spp. and Polaromonas spp. in the distribution system at T3-weeks, which were detected at rather low relative abundance at treatment plant. Though the transitional effects were captured, this study shows that the introduction of softening and additional filtration did not have an effect on the water quality for the consumer which improved considerably after 6-months’ period. The methodology of monitoring suspended particles with MuPFiSs and additional analysis is capable of detecting transitional effects by monitoring the dynamics of suspended particles and its physiochemical and microbiological composition.Sanitary Engineerin