Recommended Amendment Mixture for in Situ Treatment of Water Management Unit Groundwater, Ashtabula Closure Project

DENHAM, MILES

Savannah River Site (S.C.)

关键词: Technetium 99;    Uranium;    Flow Rate;    Mixtures;    Stabilization;   

DOI  :  10.2172/825250
RP-ID  :  WSRC-TR-2004-00185
RP-ID  :  AC09-96SR18500
RP-ID  :  825250

美国|英语

来源: UNT Digital Library

【 摘 要 】

This document provides recommendations for the composition of a mixture of peat, hydroxyapatite, and sand to treat dissolved TCE, uranium, and technetium-99 in groundwater.One option for treatment was to remove the most contaminated soil and fill the engineered excavation with amendments for in situ clean up of the groundwater. A mixture of peat and hydroxyapatite will produce conditions necessary for stabilization of uranium and technetium-99, as well as anaerobic degradation of TCE. There is an ample body of literature supporting the use of peat to maintain the methanogenic conditions required for reductive dechlorination of TCE. Likewise, peat has been used to remediate uranium in groundwater. Furthermore, reducing conditions that stabilize uranium will also stabilize technetium-99. Addition of hydroxyapatite, a natural phosphate mineral, will enhance stabilization of uranium by precipitation of low solubility phosphate phases. Hydroxyapatite will also provide phosphate, a critical nutrient, to promote microbial degradation of the peat required to maintain methanogenic conditions. This is based on the composition of WMU groundwater, the groundwater flow rate, and an assumed 30-year lifetime for the outermost meter of the treatment zone. The lifetime of the treatment system as a whole depends on the size of the treatment zone. It is recommended that laboratory treatability studies be conducted prior to any implementation of this system. The studies should focus on effectiveness and longevity. Two specific issues that may affect these are replacement of hydroxyapatite by fluorapatite and precipitation of calcite within the system.