Accumulation and Release of Trace Inorganic Contaminants from Biofilm Matrices Produced and Challenged Under Drinking Water Distribution System Conditions

Accumulation and Release of Trace Inorganic Contaminants from Biofilm Matrices Developed and Challenged under Drinking Water Distribution System Conditions by William W. Kent, Master of Science Utah State University, 2016 Major Professor: Joan McLean Department: Civil and Environmental Engineering Over the legacy time frames experienced by drinking water distribution systems (DWDS), trace inorganic contaminants (TICs) such as arsenic, lead, antimony, thallium, and chromium can accumulate in high concentrations within a biofilm matrix containing iron (Fe) and manganese (Mn) oxyhydroxides. Release of TICs can occur when these matrices are disturbed by a physical or chemical change. A bench scale factorial design using recirculating glass columns (25 mm x 300 mm) with abraded 3 mm glass beads, was used to establish biofilm matrices under a standard conditions at 16°C, 0.2 mg/l chlorine (Cl2,) and 1 mg/L dissolved organic carbon (DOC) for 6 months. The developed matrix was then challenged by altering the temperature (7 and 25°C) and concentrations of Cl2 (0 and 2 mg/L) and DOC (0 and 2 mg/L). During this 4 week challenge phase, effluent TIC concentrations were monitored, after which each column was sacrificed and analyzed for ATP and DNA, and TIC distribution within the solids using sequential extractions and total digestions. Solid phase Mn and Fe were associated with the organic fraction of the biofilm matrix. With increased Cl2, more accumulation of Mn occurred due to the oxidation of