Effect of Source Chemistry on Mn-Bearing Solid Dissolution and Reactivity in Municipal Water Systems

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Project Number:

WR14R004

Other Project Number:

2015WI325B

Funding Year:

2014

Contract Period:

7/1/2014 - 6/30/2016

Funding Source:

UWS, USGS

Investigator(s):
PIs:
  • Matthew Ginder-Vogel, UW-Madison
  • Christina Remucal, UW-Madison
Abstract:

Flushing of sediments from the water mains may result in elevated Mn concentrations in the distribution system. For example, during 2006, 17 of 1,119 sampled properties in Madison, WI had Mn levels that exceeded the lifetime health advisory value. In response to public concerns, the City of Madison conducted extensive testing of the wellheads and found that only four of the 24 wells produced water near or above the SMCL. The city initiated unidirectional flushing of the water mains and installed a treatment facility at Well 29, which had Mn levels of 124 micrograms/L. These approaches have been largely successful at limiting Mn concentrations in drinking water, yet the Mt. Simon aquifer continues to be a long-term source of dissolved manganese in municipal water systems Madison and throughout southern Wisconsin. Additionally, fundamental information concerning the solubility and reactivity of Mn-bearing solid phases in municipal water distribution systems remains sparse. The proposed research project is designed to address this gap in knowledge by developing a quantitative relationship between source chemistry and Mn-bearing solid dissolution potential and reactivity. The specific goals of the proposed project are to (1) investigate potential mineral Mn(II) sources of Mn(II) in deep aquifer materials, (2) quantify mineralogy and dissolution potential of Mn-bearing solids from the Madison Water Utility (MWU) distribution system, and (3) determine the potential of these solids to oxidize organic and inorganic pollutants. The central hypothesis of our project is that variations in source chemistry terms will have a direct, measurable impact on the stability and reactivity of Mn oxide minerals in the MWU distribution system. Our work will enable the development of a conceptual model describing Mn precipitation and dissolution reactions in the municipal water distribution system impacted by Mn derived from the Mt. Simon Aquifer.

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