Arsenic as a Water Contaminant

Arsenic typically enters the water supplies from natural deposits. It is widely believed that naturally occurring arsenic dissolves out of certain rock formations when ground water levels drop significantly. Typically, wells with higher manganese and iron can develop arsenic problems after significant water draw. Arsenic can also enter the water supply from industrial and agricultural pollution.

Arsenic commonly occurs in two forms in water: Arsenite (III) neutral charge and Arsenate (V) negative charge.

Generally, Arsenite (III) must be oxidized to Arsenate (V) prior to treatment. Effective pre-oxidants include chlorine, potassium permanganate, ozone, hydrogen peroxide and ultraviolet light.

Maximum Contaminant Level

  • EPA established MCL to 10 ppb

Public Health Concerns

Arsenic is a naturally occurring carcinogen, which is known to lead to both cancer and heart failure. Exposure to arsenic at high levels poses serious health effects. Arsenic has been reported to affect the vascular system in humans and has been associated with the development of diabetes.

WETS uses co-precipitation followed by filtration as the preferred method for removal of arsenic from drinking water. There are many methods available to remove arsenic including ion exchange, RO and adsorptive processes. However, we feel the co-precipitation process is the easiest to operate and most economical. Often, arsenic will be present in combination with iron and/or manganese. When iron and manganese are in the water, our dual filter media with right amount of coagulant and flocculant will precipitate both iron/manganese and arsenic. Our pilot study will economize on the chemical dosing and also help on getting TCEQ approval. Our solutions are unique for each plant, as we don’t offer an off-the-shelf product.

WETS Treatment

WETS uses aeration followed by filtration, with possible addition of a coagulant and flocculants. Ferric form usually precipitates at high pH.