Date of Award:

5-2016

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Committee Chair(s)

Joan McLean

Committee

Joan McLean

Committee

Laurie McNeill

Committee

David Stevens

Abstract

Drinking water distribution systems (DWDS) are used to transport drinking water from the place of treatment to your home. DWDS are made of many types of pipe materials and have the potential to accumulate materials such as iron and manganese oxides and biofilms that serve as reservoirs for toxic trace inorganic contaminants (TICs) such as thallium, arsenic, and lead. These materials can be stable, but changes in water quality or a physical disturbance such as road construction or water use changes may result in a TIC release, causing water quality degradation. This study used glass columns filled with glass beads with the purpose to accumulate biofilm material and TICs on the bead surface. Water quality parameters such as temperature, chlorine (Cl2), and dissolved organic carbon (DOC) were then changed in order to challenge the biofilm material. Analysis of the effluent and accumulated material in the columns showed the effects of temperature, Cl2, and DOC on the accumulation/release of TICs. It was observed that with increased Cl2 an increase in the retention of some TICs occurred. This was the result of the chemical reaction of Mn and Cl2, causing increased surfaces in the columns for TICs to accumulate onto. Increasing the concentration of DOC also affected the amount of accumulation in the columns, causing less accumulation of arsenic and lead in the biofilm material. No chemical parameter was shown to cause any major release into the water, but the columns did accumulate high concentrations of the contaminants. Though not the focus of this study, these highly concentrated solids are susceptible to physical disturbance and release, such as changes in consumer demand causing higher flow rates in the pipe. This study demonstrated the ease by which TICs accumulate and the importance of both minimizing accumulation and conducting regular pipe cleaning activities.

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