Arsenic in Drinking Water
Arsenic Virtual Trade Show
The main considerations when selecting a treatment technology include:
Arsenic occurs in natural waters in both inorganic and organic forms. Inorganic species such as arsenite [As(III)] and arsenate [As(V)] however, are predominant in natural waters. The relative concentration of inorganic arsenic species found in source waters is unpredictable and site specific. It is important to know the form of arsenic in your source water because studies have shown that As(V) is more effectively removed from source waters than As(III). Consequently, if the arsenic in the source water is predominately As(III), then oxidizing As(III) to As(V) with a chemical oxidant (such as chlorine) will result in a higher arsenic removal efficiency. A chemical oxidant should be selected as aeration is ineffective at oxidizing arsenic. Addition of pre-treatment such as oxidation, like any modifications to an existing treatment train, should be evaluated for potential distribution system effects.
Given various regional water quality parameters, the presence of iron (Fe) will likely play a prominent role in technology selection and the ability to treat a given water source. Because of the unique role that iron can play in facilitating arsenic removal, the level of iron in the source water is a primary consideration in the selection of an optimal treatment technology. Below is a more detailed description of the range of iron concentrations relative to arsenic concentrations and how the Fe:As ratio can influence the treatment technology chosen.
This concept, illustrated in Figure 1 below, is meant to be used as a general 'rule of thumb.' Additional guidance for treatment selection is provided under the Decide section of this site.