Arsenic Removal Studies Conducted by
Hungerford & Terry, Inc.

Hungerford & Terry, Inc. has conducted numerous pilot studies within the United States demonstrating the effectiveness of using filtration for arsenic removal, the most recent of which include municipalities in Michigan, Nevada, California, and Arizona. The principal of treatment is to co-precipitate the arsenic with iron and filter the resulting floc. Many water sources have iron naturally occurring in the water and require treatment before use. In such instances, the water can be treated for both iron and arsenic using the same equipment. Applications that do not have iron, or have insufficient iron to adequately reduce the arsenic, can use ferric chloride to supplement the treatment process.

H&T has treated water sources with various arsenic levels.  The highest arsenic levels have been encountered in the more arid regions of the United States, i.e. Southwest United States.  Regardless of the arsenic concentration, it was readily treated by complexing the arsenic with iron and directly filtering the constituents together.  The arsenic ranged from as low as 12 ppb to as high as over 80 ppb.  The arsenic was typically reduced to 3-4 ppb, often reaching non-detectable levels. 

The species state of arsenic can impact the removal efficiency.  Arsenite (As⁺³) must first be converted to Arsenate (As⁺⁵) to best utilize this technology. The conversion to As⁺⁵ is known to be easily accomplished with chlorine.  The conversion, if any, represents a minimal chlorine demand given the fact that arsenic concentrations are low compared to any iron that is typically present.  Additionally, the amount of chlorine required for maintaining a disinfected system is magnitudes of order greater than the typical arsenic concentration. 
 

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