Techniques and technologies for decontaminating chemically contaminated premise plumbing infrastructure
Abstract
Recent large-scale drinking water chemical contamination incidents in Canada and the U.S. have affected more than 1,000,000 people. In all cases premise plumbing has become contaminated and disparate plumbing decontamination approaches have been applied. Premise plumbing components include the service line and piping within the building as well as various appurtenances (i.e., tanks, valves, fixtures). The overall research goal was to identify techniques and technologies that can be used for premise plumbing decontamination. To achieve this goal two separate studies were conducted and are presented as two independent thesis chapters. The study described in Chapter 1 was designed to understand current knowledge associated with premise plumbing contamination and create a rationale for science based water flushing protocols. Objectives were to (1) review past premise plumbing contamination incidents and the decontamination approaches applied, and (2) develop and test a mass balance water heater model. Thirty-nine drinking water contamination incidents were identified that involved a wide range of contaminants. Results showed that plumbing system design, operational conditions, contaminant properties, as well as building inhabitant safety have not been fully considered in premise plumbing flushing protocol design. Flushing could decontaminate some, but not all plumbing systems and poorly designed procedures likely caused residents to become ill during some incidents. Several water heater modeling scenarios showed that contaminant levels could exceed drinking water health limits after flushing and water saving fixtures, devices, water heater size, and flow rate affected contaminant removal efficiency. The study described in Chapter 2 was conducted to examine the effectiveness of surfactants to decontaminate plastic plumbing components. Objectives of this study were to: (1) determine the impact of Alconox® detergent, Dawn® soap, and MAG IT DG 100 surfactant solutions on the strength, dimension, and mass of ethylene propylene diene monomer (EPDM), cross-linked polyethylene (PEX), high-density polyethylene (HDPE), and low-density polyethylene (LDPE) plastics, and (2) determine the effectiveness of Alconox® detergent solution for decontaminating PEX-a and copper pipes exposed to crude oil contaminated water. Results showed that MAG solution constituents, at room temperature, permeated all plastics within 3 days, but EPDM was the most affected (+45% weight; +43% volume; -82% tensile strength). Results of these studies provide a better understanding of premise plumbing contamination as well as decontamination techniques, approaches, and technologies. In response to future drinking water contamination incidents, premise plumbing decontamination procedures should be based on water heater modeling, pilot-, and field-testing. Also recommended is that flushing procedures be developed that consider system design, operation, organic contaminant properties, and building inhabitant safety. In particular, plastic components exposed to crude oil contaminated water pose a unique challenge to returning contaminated plumbing to safe use. Additional decontamination studies are recommended that involve other plastics, contaminants, and surfactants. Studies should also examine the role of temperature and flow/mixing on decontamination effectiveness. Results from this study show that current decontamination practices can degrade plastics (e.g., mechanical strength, oxidative resistance) and can leave residual surfactant compounds in the plastics. While in-situ cleaning of plastic plumbing components is preferred, component removal and replacement should be considered. (Abstract shortened by ProQuest.)
Degree
M.S.C.E.
Advisors
Whelton, Purdue University.
Subject Area
Civil engineering|Environmental engineering|Materials science
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