AWWA WKICO66067

To address hypolimnetic anoxia and the subsequent transfer of dissolved Fe and Mn to the bulk water, the Western Virginia Water Authority (WVWA) installed an oxygenation system in Carvin's Cove Reservoir (CCR). Following the installation of the oxygenation system, the concentrations of both Fe and Mn were substantially decreased in CCR, indicating that source water control of dissolved metals can be accomplished with hypolimnetic oxygenation. Hypolimnetic oxygenation maintained dissolved Mn concentrations in the bulk water at or below the U.S. Environmental Protection Agency secondary maximum contaminant level (SMCL) throughout the 2007 stratified period, minimizing the transport of Mn from the benthic region to the bulk water. This was achieved by maintaining elevated dissolved oxygen (DO) as well as mixing. Oxygenation also appeared to facilitate the oxidation and precipitation of Mn prior to destratification in the event Mn did transfer to the bulk water (from upstream regions where water is in contact with relatively anoxic sediments). If operated correctly, oxygenation can be used to manage Mn in the source water, substantially reducing the amount that has to be removed during the treatment process. Includes 9 references, figures.