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Treatment Of Arsenic-Contaminated Materials Using Selected Stabilization And Solidification Technologies
Citation:
RANDALL, P. Treatment Of Arsenic-Contaminated Materials Using Selected Stabilization And Solidification Technologies. Presented at 26th Annual International Conference on Soils, Sediments, Water, and Energy, Amherst, MA, October 18 - 21, 2010.
Impact/Purpose:
To focus on two types of solidification/stabilization techniques to contain the long term leaching potential of arsenic after disposal.
Description:
Arsenic contamination of soil, sediment and groundwater is a widespread problem in certain areas and has caused great public concern due to increased awareness of the health risks. Often the contamination is naturally occurring, but it can also be a result of waste generated from industrial processes. EPA's lowering of the drinking water maximum contaminant level (MCL) for arsenic resulted in the reassessment and development of better treatment methods. Arsenic contaminated hazardous wastes are subject to land disposal restrictions under Resource Conservation and Recovery Act (RCRA) and must be treated to meet toxicity characteristic leaching procedure (TCLP) limits. The present study focuses on two types of solidification/stabilization technologies to contain the long term leaching potential of arsenic after disposal. Three types of arsenic contaminated materials were selected: a) Montana soil spiked with monosodium acid methanearsonate, b) composite sample from La Trinidad (California) mine tailings sediment deposits, and c) chromated copper arsenate (CCA) wood treated waste or door pit residue from Osmose, Inc. These three samples were treated with two technologies: TerraBond®, a commercially available technology; and Portland cement with addition of ferrous sulfate and lime (PFL). The treatment procedure followed for the second method was obtained from available peer reviewed literature search. Characterizations of sample materials were conducted by analyzing the particle size, moisture content, and conducting XRD and SEM analyses. The leachability of untreated and treated samples was evaluated by conducting a) variable pH based leach test, b) TCLP test, and c) semi dynamic leach test. Extended X ray absorption fine structure (EXAFS) spectroscopic analysis was conducted to identify the differences of As coordination between samples before and after treatment process. Sequential extraction test was also conducted to obtain a quantifiable idea of the amount of arsenic present in different phases. The results obtained from these studies give insightful details about the leachability and mobility of arsenic in the sample. Though both treatment methods reduced the arsenic mobility, the effectiveness of these treatments varied significantly for different types of contaminant matrix. This paper will present the results of this study.