Impact of Pipe Size and Contaminant Properties on Persistence of Organic Chemicals in Polyethylene Water Pipes - Dallas, TX
Citation:
Haupert, L. AND M. Magnuson. Impact of Pipe Size and Contaminant Properties on Persistence of Organic Chemicals in Polyethylene Water Pipes - Dallas, TX. Water Quality Technology, Dallas, Texas, November 03 - 07, 2019.
Impact/Purpose:
For reasons including cost and mechanical performance, polyethylene pipes are increasingly being used in building water systems, water distribution networks, and as water service lines. However, compared to materials like copper or ductile iron, polyethylene is vulnerable to permeation by organic contaminants. Polyethylene that has been permeated by organic contaminants can continue to desorb those contaminants even after the original contaminant source has been removed, extending the persistence of the potential impact of a contamination incident. Organic contaminants can be introduced into water systems following incidents such as chemical spills, back-siphoning, or sabotage. Recently, at least two incidents of benzene contamination following damage by wildfires have occurred in California. Following these contamination incidents, flushing was employed during remediation. However, flushing protocols do not necessarily consider the complicating effects caused by permeated polyethylene infrastructure. The kinetics of contaminant migration from pipes permeated by persistent, wide-area spills or other chronic contaminant sources have been previously studied in detail. In these situations, flushing is generally considered ineffective. Additionally, the time required for permeation to occur scales with the square of pipe wall thickness. Therefore, thicker pipe is expected to be more resistant to permeation from the outside. However, the kinetics of transient sorption and desorption of organic contaminants in polyethylene, especially from contamination sources inside the distribution system, remain largely unstudied. Accordingly, the viability of flushing as a decontamination approach, and the effect of pipe dimensions on that viability, are difficult to definitively judge. In this work, we employ an experimentally calibrated, numerical method to estimate the effect of pipe dimensions and contaminant properties on the flushing time required to remediate contaminated polyethylene tubing. Results of our work suggest that, the effect of pipe diameter on decontamination kinetics is expected to be nonlinear and dependent on wall thickness and the partition factor between the contaminant and the pipe material. Model predictions will be presented to assist decision-makers in contamination situations involving permeated polyethylene pipes.
Description:
For reasons including cost and mechanical performance, polyethylene pipes are increasingly being used in building water systems, water distribution networks, and as water service lines. However, compared to materials like copper or ductile iron, polyethylene is vulnerable to permeation by organic contaminants. Polyethylene that has been permeated by organic contaminants can continue to desorb those contaminants even after the original contaminant source has been removed, extending the persistence of the potential impact of a contamination incident. Organic contaminants can be introduced into water systems following incidents such as chemical spills, back-siphoning, or sabotage. Recently, at least two incidents of benzene contamination following damage by wildfires have occurred in California. Following these contamination incidents, flushing was employed during remediation. However, flushing protocols do not necessarily consider the complicating effects caused by permeated polyethylene infrastructure. The kinetics of contaminant migration from pipes permeated by persistent, wide-area spills or other chronic contaminant sources have been previously studied in detail. In these situations, flushing is generally considered ineffective. Additionally, the time required for permeation to occur scales with the square of pipe wall thickness. Therefore, thicker pipe is expected to be more resistant to permeation from the outside. However, the kinetics of transient sorption and desorption of organic contaminants in polyethylene, especially from contamination sources inside the distribution system, remain largely unstudied. Accordingly, the viability of flushing as a decontamination approach, and the effect of pipe dimensions on that viability, are difficult to definitively judge. In this work, we employ an experimentally calibrated, numerical method to estimate the effect of pipe dimensions and contaminant properties on the flushing time required to remediate contaminated polyethylene tubing. Results of our work suggest that, the effect of pipe diameter on decontamination kinetics is expected to be nonlinear and dependent on wall thickness and the partition factor between the contaminant and the pipe material. Model predictions will be presented to assist decision-makers in contamination situations involving permeated polyethylene pipes.