Consultant's Corner: Arsenic Removal — Lessons Learned Since 2002

By Lee Odell, Water Treatment Global Technology Lead, CH2M HILL, and Sam Perry, Water Treatment Engineer, Washington State Department of Health

In the United States, arsenic has been regulated in drinking water since 1942, when a standard of 50 ug/L was set.  In 1962, the U.S. Public Health Service recommended lowering the drinking water standard to 10 ug/L, but it wasn’t until 2001 when the U.S. Environmental Protection Agency (EPA) promulgated the final arsenic primary drinking water maximum contaminant level (MCL) of 10 ug/L that became effective February 22, 2002.  Since that time many research projects, health effects studies, and deployments of new technologies have been completed.  The purpose of this article is to try to summarize the key findings from the last 10 years of industry work on arsenic removal.

Arsenic Occurrence
Arsenic is found in surface water and groundwater as a result of natural processes such as the weathering of minerals and microbial activities. Major anthropogenic sources include mining, particularly smelting, and pesticide manufacture and use. A variety of industries also use arsenic compounds in their production processes.

Generally, naturally occurring arsenic concentrations are below 1 ug/L.  Higher concentrations are found in localized zones of contamination. Inorganic forms of arsenic are most common, although organic arsenic compounds associated with microbial activity and pesticide manufacture do occur. Significant concentrations of organic arsenic are generally not found in groundwater used for drinking water supply.

Lessons Learned
A lot has been learned about arsenic treatment since the Arsenic Rule became effective.  One of the most detailed sources of information has been the EPA Arsenic Removal Technology Demonstration Program that was initiated in 2002.  The EPA reports from the field demonstrations provide a wealth of information on lessons learned, costs of treatment, and operational adjustments that helped improve treatment performance...