Grantee Research Project Results
2014 Progress Report: Association of Pathogens with Biofilms in Drinking Water Distribution Systems
EPA Grant Number: R834870Title: Association of Pathogens with Biofilms in Drinking Water Distribution Systems
Investigators: Nguyen, Thanh (Helen) H. , Hozalski, Raymond , Liu, Wen-Tso
Institution: University of Illinois Urbana-Champaign , University of Minnesota
EPA Project Officer: Packard, Benjamin H
Project Period: June 1, 2011 through May 28, 2016
Project Period Covered by this Report: June 1, 2014 through May 28,2015
Project Amount: $600,000
RFA: Advancing Public Health Protection through Water Infrastructure Sustainability (2009) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
Objective:
- To investigate how drinking water biofilm mechanical and structural properties responded to long-term disinfectant exposure.
- To explore the effect of long-term disinfection on release of biofilms and biofilm-associated pathogens in a drinking water distribution system.
- To identify the hydrodynamic condition in a drinking water distribution system on biofilm mechanical and structural properties.
- To address the public health risk due to pathogen and biofilm release in the distribution system.
Progress Summary:
- We identified how the biofilm mechanical and structural properties change during long-term disinfectant exposure. Specifically, elastic modulus and structure of groundwater biofilms was monitored by atomic force microscopy (AFM) and optical coherence tomography (OCT) during 3 months of exposure to monochloramine or free chlorine. After the first month of disinfectant exposure, the mean stiffness of monochloramine or free chlorine treated biofilms was 4 to 9 times higher than those before treatment. In the meanwhile, biofilm thickness decreased from 120 ± 8 mm to 93 ± 6 -107 ± 10 mm. The increased surface stiffness and decreased biofilm thickness within the first month of disinfectant exposure was presumably due to oxidation of the biofilms. However, by the second to third month during disinfectant exposure, the biofilm mean stiffness showed 2 to 4-fold decrease while the biofilm thickness increased to 110 ± 7 -129 ± 8 mm, suggesting that the biofilms adapted to disinfectant exposure.
- We addressed the effect of long-term disinfection on biofilm elastic modulus and structure. The disinfected biofilms and non-disinfected biofilms showed statistically similar thickness (t-test, p > 0.05), suggesting that long-term disinfection may not significantly remove net biomass. However, by 3 months of the disinfectant exposure process, the disinfected biofilms showed 2-5 times higher mean stiffness (as determined by AFM) and 6-13 fold higher ratios of protein over polysaccharide, as determined by differential staining and confocal laser scanning microscopy (CLSM), than the non-disinfected groundwater biofilms.
- Shear conditions were found to flatten biofilms during disinfectant exposure due to the biofilm erosion caused by shear stress. These smoother biofilms were expected to be more resistant to shear force and detachment.
Future Activities:
- The detachment kinetics of pre-adhered Legionella pneumophila from disinfected biofilms will be monitored by fluorescent microscopy. The cultivability and infectivity of the detached Legionella pneumophila will be tested by plate counting and qPCR.
- The effect of calcite precipitation in biofilms will be investigated. Biofilms will be developed from feed water with and without high hardness. The mechanical properties of these biofilms will be measured using atomic force microscopy (AFM) and rheometer. The structure of these biofilms and the detachment of biofilms under shear stress will be examined by optical coherence tomography (OCT).
- Long-term adhesion and detachment of L. pneumophila in a pipe system will be studied.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 8 publications | 4 publications in selected types | All 4 journal articles |
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Type | Citation | ||
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Shen Y, Monroy GL, Derlon N, Janjaroen D, Huang C, Morgenroth E, Boppart SA, Ashbolt NJ, Liu W-T, Nguyen TH. Role of biofilm roughness and hydrodynamic conditions in Legionella pneumophila adhesion to and detachment from simulated drinking water biofilms, Environmental Science & Technology 2015;49(7):4274-4282. |
R834870 (2014) |
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Supplemental Keywords:
Drinking water, pathogen, biofilms, drinking water distribution system;Relevant Websites:
Association of Pathogens with Biofilms in Drinking Water Distribution Systems | Global Water and Food Safety ExitProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.