Role of Extracellular Polymeric Substances (EPS) on Biofilm Disinfection in a Model Drinking Water Distribution System

Biofilms are undesirable but ubiquitous in drinking water systems. This study investigated the role of extracellular polymeric substances (EPS) in the biofilm life cycle, including planktonic cells, attached biofilm, detached biofilm clusters and redistributed biofilm, in a model distribution system with minimal disinfectant residuals. EPS contributed to bacterial surface properties, biofilm structural characteristics, disinfectant diffusion and reaction, organic matter retention and utilization, hence playing pivotal roles in bacterial resistance to disinfectants. Strains from an opportunistic pathogen, Pseudomonas aeruginosa with different EPS secretion capabilities were tested. Two major components in P. aeruginosa EPS, polysaccharides and proteins, both reacted rapidly with chlorine while monochloramine reacted specifically with proteins. The impact of biofilm EPS reactivity with disinfectants on disinfection efficacy was evaluated by monitoring planktonic bacteria viability, disinfectant decay, biofilm viability, biofilm structure, and detached biofilm viability as well as their redistribution, systematically during the disinfection process. The obtained results suggested that the presence of EPS increased the resistance of planktonic bacteria, biofilm and detached biofilm to both chlorine and monochloramine. The EPS reactivity led to different protection approaches for bacterial cells, acting either as a disinfectant consumer (for chlorine inactivation) or limiting access to reactive sites on a cell membrane (for monochloramine inactivation). The biofilm structure characterization using confocal laser scanning microscopy (CLSM) revealed that EPS production affected biofilm structure, specifically surface roughness, surface area to volume ratio and average diffusion distance. These structural characteristics were closely related to overall biofilm viability and the spatial distribution of viability within biofilms. Although the overall viable ratios were similar under the two disinfectants for each strain, monochloramine penetrated deeper into biofilm matrix than chlorine regardless the quantity of EPS content, showing a higher inactivation efficacy in the middle section of biofilms. However, chlorine was more efficient in controlling planktonic and detached cluster viability than monochloramine. The combined results suggested that different reactivity of biofilm EPS with disinfectants influenced the susceptibility of both biofilm and detached biofilm during the disinfection practices. This study provides valuable insight for both fundamental studies of biofilm life cycle and disinfection practices to optimize water quality maintenance in distribution systems.

Name thesis:degree_name

Doctor of Philosophy in Engineering

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Civil Engineering

Grantor dc:publisher

University of Toledo

Year dc:date

2012

Author dc:creator

• XUE, ZHENG

Contributors dc:contributor

• Seo, Youngwoo

• Civil Engineering
• Environmental Engineering

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=toledo1349714910

OAI identifier oai:identifier

oai:etd.ohiolink.edu:toledo1349714910