Adhesion and Decontamination of Biological Contaminants in Drinking Water Distribution Systems

Abstract

The introduction of pathogenic biological contaminants into a water distribution system may result in short-term and long-term exposures and subsequent effects on human health if these contaminants adhere to the internal surfaces of pipes, potentially forming biofilms. These studies evaluated the degree to which selected biological contaminants representative of biological warfare threats or natural contamination adhere to water distribution system pipe materials under different temperature and exposure conditions, and whether water distribution pipes can be remediated using common chemical treatment procedures. The adherence levels of Bacillus anthracis spores, Burkholderia thailandensis, Vibrio cholerae, Salmonella enterica subsp. enterica serovar Typhi (referred to as S. typhi), aflatoxin, and brevetoxin to seven pipe materials were evaluated. Most of the biological contaminants tested were shown to have some level of adherence to high-density polyethylene (HDPE), polyvinyl chloride (PVC), aged black iron pipe (ACI), and steel pipe coated with epoxy (DIE) pipe materials using a single test concentration of organisms or toxin after incubation for 7 days at room temperature. Of the seven materials tested, HDPE appeared to be the most adherent pipe material with some levels of adherence measured for all six of the biological contaminants. Shortened incubation times appeared to reduce the overall adherence for three of the biological contaminants evaluated. Three chemical treatments (sodium hypochlorite, Pipe-Klean®, and Simple Green®) were evaluated for their ability to remediate these biological contaminants from selected pipe material/biological contaminant combinations. Sodium hypochlorite was the most effective for reducing the adherence of the bacteria and B. anthracis spores but not as effective against aflatoxin as the other treatments. Remediation of these organisms in model systems needs to be further evaluated to better understand effective potable water-decontamination methods.