Date of Graduation

12-2018

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

Zhang, Wen

Committee Member

Carbonero, Franck G.

Second Committee Member

Jiang, Hua

Keywords

Biofilm; Drinking Water; Drinking Water Distribution System; Lead

Abstract

Recent crises, such as the one in Flint, MI, indicate that lead exposure from drinking water is a major health concern in the United States. Over six million lead service lines are still in use in the United States, and a universal protocol to safely remove these lead service lines from drinking water distribution systems has not yet been established. This paper calls to attention the potential hazard that biofilms pose as a source of lead in distribution systems, even after the removal of lead pipes. This study used a simulated water distribution system containing a lead source pipe and various pipe materials with periodic flow and stagnation conditions of a typical household to create, characterize, and determine lead accumulation capabilities of biofilms within the water pipes. Biofilms developed in all pipe materials with an overall range of 1.44×103 to 5.90×105 gene copies per cm2 of pipe surface. Pipe material affected the biofilm growth with plastic pipes supporting higher quantities of biofilms. Biofilms accumulated lead in all pipe materials with a maximum accumulation of 25.22 µg/cm2. In addition, all pipe trains experienced an increase in lead accumulation immediately following the removal of the lead source with a maximum increase of 21.42 µg/cm2 in the galvanized steel pipe and then a gradual decrease during a period of one month afterward. The lead source also had an effect on the microbiome of the biofilms collected during the project. One genus specifically, Sphingobium, increased in all pipe materials following the removal of lead. This research provides valuable information regarding the timing and process of safe lead service line removal from drinking water distribution systems and helps minimize the human exposure to lead contamination within drinking water.

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