Sequestration for iron and manganese is effective in groundwater that has what characteristic?

• A. High levels of dissolved oxygen
• B. High concentration of iron and manganese
• C. Low level of dissolved iron and manganese and no dissolved oxygen
• D. Variable levels of dissolved solids

Answer: (C)

Sequestration for iron and manganese is particularly effective in groundwater characterized by low levels of dissolved iron and manganese combined with no dissolved oxygen. In cases where there is no dissolved oxygen present, iron and manganese tend to remain in a soluble, reduced state, making it easier to convert and stabilize them through sequestration methods, such as using polyphosphate or other sequestrants that inhibit their oxidation and precipitation.

In contrast, when groundwater contains high concentrations of iron and manganese, the effectiveness of sequestration can be compromised due to the abundance of these metals, leading to more significant treatment challenges. High levels of dissolved oxygen can cause both iron and manganese to oxidize, resulting in precipitation that can exacerbate issues in treatment and distribution systems. If groundwater has variable levels of dissolved solids, this inconsistency does not pave the way for effective sequestration because the interaction of various ions and compounds can alter the conditions under which iron and manganese exist in the water. Therefore, the absence of dissolved oxygen is crucial for optimal sequestration in this context.