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Kundu A.,University of California at Davis | McBride G.,NIWA - National Institute of Water and Atmospheric Research | Wuertz S.,University of California at Davis | Wuertz S.,Singapore Center on Environmental Life science Engineering | Wuertz S.,Nanyang Technological University
Water Research | Year: 2013

We used site-specific quantitative microbial risk assessment (QMRA) to assess the probability of adenovirus illness for three groups of swimmers: adults with primary contact, children with primary contact, and secondary contact regardless of age. Human enteroviruses and adenoviruses were monitored by qPCR in a multi-use watershed and Adenovirus type 40/41 was detected in 11% of 73 samples, ranging from 147 to 4117 genomes per liter. Enterovirus was detected only once (32 genomes per liter). Seven of eight virus detections occurred when E. coli concentrations were below the single sample maximum water quality criterion for contact recreation, and five of eight virus detections occurred when fecal coliforms were below the corresponding criterion. We employed dose-harmonization to convert viral genome measurements to TCID50 values needed for dose-response curves. The three scenarios considered different amounts of water ingestion and Monte Carlo simulation was used to account for the variability associated with the doses. The mean illness risk in children based on adenovirus measurements obtained over 11 months was estimated to be 3.5%, which is below the 3.6% risk considered tolerable by the current United States EPA recreational criteria for gastrointestinal illnesses (GI). The mean risks of GI illness for adults and secondary contact were 1.9% and 1.0%, respectively. These risks changed appreciably when different distributions were fitted to the data as determined by Monte Carlo simulations. In general, risk was at a maximum for the log-logistic distribution and lowest for the hockey stick distribution in all three selected scenarios. Also, under default assumptions, the risk was lowered considerably when assuming that only a small proportion of Adenovirus 40/41 (3%) was as infectious as Adenovirus type 4, compared to the assumption that all genomes were Adenovirus 4. In conclusion, site-specific QMRA on water-borne adenoviruses in this watershed provided a similar level of protection against public health risks as would be obtained by enumeration of fecal indicator bacteria under the new U.S. EPA guidelines. © 2013 Elsevier Ltd. Source


Zhang X.,Dublin City University | Zhang X.,CAS National Center for Nanoscience and Technology | Epifanio M.,Dublin City University | Marsili E.,Dublin City University | Marsili E.,Singapore Center on Environmental Life science Engineering
Electrochimica Acta | Year: 2013

High specific surface and electrocatalytic activity of the electrode surface favour extracellular electron transfer from electrochemically active biofilms to polarized electrodes. We coated layer-by-layer carbon nanotubes (CNTs) on graphite electrodes through electrophoretic deposition, thus increasing the electrocatalytic activity. After determining the optimal number of CNT layers through electrochemical methods, we grew Shewanella loihica PV-4 biofilms on the CNT-coated electrodes to quantify the increase in extracellular electron transfer rate compared with unmodified electrodes. Current density on CNT-modified electrodes was 1.7 times higher than that observed on unmodified electrodes after 48 h from inoculation. Rapid microbial cells attachment on CNT-coated electrodes, as determined from scanning electronic microscopy, explained the rapid increase of the current. Also, the CNT reduced the charge transfer resistance of the graphite electrodes, as measured by Electrochemical Impedance Spectroscopy. However, the electrocatalytic activity of the CNT-coated electrode decreased as the biofilm grew thicker and covered the CNT-coating. These result confirmed that surface-modified electrodes improve the electron transfer rate in thin biofilms (<5 μm), but are not feasible for power production in microbial fuel cells, where the biofilm thickness is much higher. © 2013 Elsevier Ltd. All rights reserved. Source


Fazi S.,CNR Water Research Institute | Bandla A.,Singapore Center on Environmental Life science Engineering | Bandla A.,National University of Singapore | Pizzetti I.,CNR Water Research Institute | And 2 more authors.
Ecohydrology and Hydrobiology | Year: 2016

Fluvial corridors such as streams and urban canals are critical components of the landscape and are key ecohydrological assets. They are essential to landscape function and are vulnerable to anthropogenic pressures. Energy and nutrient budgets in such corridors are dominated by processes associated with detrital organic matter and are mediated by microorganisms that mainly reside in biofilms. Here, we review the major hydrologic factors shaping biofilms in natural and urban water corridors, and propose the integration of single-cell visualization techniques with other broad-scale approaches (genomics) to better understand structure-function coupling in such complex microbial communities. We, further, provide evidence that it is possible to visualize specific bacterial clusters and autotrophic microorganisms within the matrix of natural biofilms from urban canals. This can then guide the development of ecohydrological approaches and management interventions to harness ecological services mediated by biofilms, with enormous implications also by a sanitary point of view. © 2015 Published by Elsevier Sp. z o.o. on behalf of European Regional Centre for Ecohydrology of the Polish Academy of Sciences. Source


Saxena G.,Singapore Center on Environmental Life science Engineering | Saxena G.,National University of Singapore | Marzinelli E.M.,Singapore Center on Environmental Life science Engineering | Marzinelli E.M.,University of New South Wales | And 20 more authors.
Environmental Science and Technology | Year: 2015

Networks of engineered waterways are critical in meeting the growing water demands in megacities. To capture and treat rainwater in an energy-efficient manner, approaches can be developed for such networks that use ecological services from microbial communities. Traditionally, engineered waterways were regarded as homogeneous systems with little responsiveness of ecological communities and ensuing processes. This study provides ecogenomics-derived key information to explain the complexity of urban aquatic ecosystems in well-managed watersheds with densely interspersed land-use patterns. Overall, sedimentary microbial communities had higher richness and evenness compared to the suspended communities in water phase. On the basis of PERMANOVA analysis, variation in structure and functions of microbial communities over space within same land-use type was not significant. In contrast, this difference was significant between different land-use types, which had similar chemical profiles. Of the 36 environmental parameters from spatial analysis, only three metals, namely potassium, copper and aluminum significantly explained between 7% and 11% of the variation in taxa and functions, based on distance-based linear models (DistLM). The ecogenomics approach adopted here allows the identification of key drivers of microbial communities and their functions at watershed-scale. These findings can be used to enhance microbial services, which are critical to develop ecologically friendly waterways in rapidly urbanizing environments. © 2015 American Chemical Society. Source

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