The Minimization Of Wastes Produced During The Treatment Of Arsenic Contaminated Drinking Water

Abstract

Arsenic in potable groundwater is a major concern in the United States and many remediation strategies are being utilized to reduce arsenic levels to below the Environmental Protection Agency’s maximum contaminant level of 10 µg/L. The most popular technology is adsorption, where the arsenic species in the groundwater are adsorbed onto a solid metal oxide phase which is ultimately disposed of directly into a landfill. Standard adsorptive media are generally not regenerated due to poor mechanical strength and huge volumes of solid waste are generated annually, typically with arsenic contents of a few milligrams per gram of material. These wastes, which usually pass the Environmental Protection Agency’s (EPA) Toxic Characteristic Leaching Procedure (TCLP), are disposed of as non-hazardous wastes. Recent research has indicated that the adsorbed arsenic is mobilized under reducing landfill conditions and can migrate back into the groundwater supply. Consequently, the current method of disposal of large volumes of arsenic-bearing wastes may have a major environmental impact in the future. This paper discusses the advantages of regenerating a more durable iron-based adsorbent media using a strong caustic solution to strip and concentrate the arsenic in a small volume of liquid and return the media to service. The stripped arsenic is then precipitated to generate a much smaller volume of solid and disposed of as a hazardous waste. This greatly reduces the total volume of solid waste generated during the arsenic treatment process.