375786 - Kinetics of Decontamination of Plastic Drinking Water Pipe by Flushing
Wednesday, June 6
8:30 AM - 10:00 AM
Location: Lakeshore C
Matthew Magnuson, Cincinnati, OH – EPA
Polymeric materials such as polyethylene, polypropylene, and polyvinylchloride (PVC) are used extensively for drinking water applications. These materials are subject to permeation by organic compounds such as those found in petroleum products and industrial chemicals, which can result in water quality issues with potential health effects. Although flushing is a common decontamination technique, the scientific literature suffers from disagreements and gaps for important governing parameters such as the diffusion and partition coefficients of organic molecules in polymers, complicating prediction of how much flushing may be required to address organic contamination incidents. We employ a combination of analytical and numerical solutions to the diffusion equation to predict flushing decontamination times for a variety of organic molecules in polyethylene, polypropylene, and PVC for several real life scenarios. A flow-through fluorometer and a custom built pipe loop apparatus are used to validate the diffusion model and to determine important parameters such as the diffusion and partition coefficients for specific polymer/contaminant systems. The results of our work predict that, for pipe wall thicknesses typically used for drinking water, heavily permeated tubing is expected to be resistant to decontamination by flushing, possibly requiring weeks or months of continuous flushing to remove fifty percent of contamination. However, this time requirement may be greatly reduced if contamination is detected early and flushing is started before permeation of the pipe wall becomes extensive. The findings of this study are expected to assist water utilities in selecting appropriate solutions when responding to contamination incidents.