Grantee Research Project Results

Final Report: Association of Pathogens with Biofilms in Drinking Water Distribution Systems

EPA Grant Number: R834870
Title: 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 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 drinking water distribution system.
To identify the hydrodynamic condition in 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.

Conclusions:

First, the biofilm roughness was proved to enhance the adhesion of L. pneumophila to biofilms and prevent the release of L. pneumophila from biofilms. The adhesion of L. pneumophila was observed to positively correlate with biofilm roughness due to enlarged biofilm surface area and local flow conditions created by roughness asperities. The release of L. pneumophila from smoother biofilms was higher than that from rougher biofilms, presumably because of the low shear stress zones near roughness asperities. Biofilm physical structure was identified as a key factor influencing L. pneumophila adhesion to and release from simulated drinking water biofilm.

Second, long-term disinfectant exposure could not reduce biofilm thickness. However, the biofilms were stiffened after long-term disinfectant exposure. Within a relative short term disinfectant exposure (1 month), biofilms were stiffened and thinned. However, the biofilms became softer and thicker again with longer disinfectant exposure (2-3 months), suggesting that biofilms microbial communities can adapt to disinfectant exposure. Overall, the biofilm thickness before and after 3 months of disinfection was similar, while the biofilm stiffness after 3 months disinfection was higher than that before disinfection. These stiffened biofilms after disinfectant would have better resistance to flow shear stress, thus less biofilm detachment and less biofilm-associated pathogen release would be expected.

Third, compared to the pre-disinfected biofilms, the non-disinfected biofilms can provide better protection for L. pneumophila from disinfection. In DWDS, biofilms are possible to be continuously exposed to disinfectant (pre-disinfected biofilms) or rarely exposed to disinfectant (non-disinfectant biofilms). When the fresh drinking water containing disinfectant flow through those biofilms, the L. pneumophila associated with biofilms could be released and disinfected. The inactivation of L. pneumophila released from pre-disinfected biofilms was higher than that from non-disinfected biofilms; while the infectivity of L. pneumophila released from pre-disinfected biofilms was lower than non-disinfected biofilms. Non-disinfected biofilms can provide better protection for L. pneumophila under disinfectant exposure, probably because more biofilm materials detached from the softer non-disinfected biofilms, surrounded the released L. pneumophila, and separated the L. pneumophila from disinfectant.

Fourth, reducing water hardness and applying scale inhibitor to water diminished the calcium carbonate precipitating inside biofilms, thus led to biofilms with low stiffness. On the contrary, biofilms developed from high hardness groundwater had the high content of calcium carbonate precipitation, thus showed the high stiffness. While the scale inhibitor (polyphosphate) can facilitate the growth of microorganisms, thick biofilms were developed from groundwater containing scale inhibitor. These thick and soft biofilms would be expected to release more microorganisms in DWDS, thus cause drinking water microbial safety concern.

Fifth, the treatment by the detachment promoting agents (DPA), including sodium triphosphate [STP], ethylene diamine tetraacetate [EDTA], citrate and urea, was impractical for removing established biofilms in drinking water distribution systems because of the high DPA concentrations needed. Additionally, our results revealed multi-species biofilms to be more resistant to DPA treatments; highlighting a limitation of a ‘reductionist’ approach involving single-species biofilms to understand the behavior of complex real-world biofilms

Journal Articles on this Report : 2 Displayed | Download in RIS Format

Publications Views
Other project views:	All 8 publications	4 publications in selected types	All 4 journal articles

Publications
Type	Citation	Project	Document Sources
Journal Article	Shen Y, Huang P, Huang C, Sun P, Monroy G, Wu W, Lin J, Espinosa-Marzal R, Boppart S, Liu W, Nguyen T. Effect of divalent ions and a polyphosphate on composition, structure, and stiffness of simulated drinking water biofilms. NPJ BIOFILMS AND MICROBIOMES 2018;4(15).	R834870 (Final)	Full-text from PubMed Abstract from PubMed Full-text: Nature - Full Text PDF Exit Other: Nature - Full Text PDF Exit
Journal Article	Sun P, Araud E, Huang C, Shen Y, Monroy G, Zhong S, Tong Z, Boppart S, Eden J, Nguyen T. Disintegration of simulated drinking water biofilms with arrays of microchannel plasma jets. NPJ BIOFILMS AND MICROBIOMES 2018;4(24).	R834870 (Final)	Full-text from PubMed Abstract from PubMed Full-text: Nature - Full Text HTML Exit Other: Nature - Full Text PDF Exit

Supplemental Keywords:

drinking water, pathogen, biofilm, water distribution system;

Relevant Websites:

Association of Pathogens with Biofilms in Drinking Water Distribution Systems | Global Water and Food Safety | University of Illinois Exit

Progress and Final Reports:

Original Abstract

The 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.