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COMPLEX REMEDIATION OF MERCURY CONTAMINATED SOIL ON A SENSITIVE SITE
Leplat, J., J. Chibleur, and J. Haemers.
Intersol 2018: International Conference-Exhibition on Soils, Sediments and Water, March 27-29, 31 slides, 2018

Mercury was a major contaminant of concern at a former industrial site in a highly urbanized area in the south Paris region where redevelopment aimed to accommodate future public use. Lab studies showed it was possible to differentiate several forms of Hg (mainly HgCl and Hg0) and validated the possibility of desorbing Hg in these forms at ~260°C. That temperature mitigated the residual risk of subsequent Hg vapors, as only stable HgS remained in the soil. Soil excavations carried out in 2016-2017 included work in the vicinity of sensitive structures, particularly a buried high-voltage line. Nearly 12,000 m3 were excavated and disposed of off site: 80% as non-hazardous waste, 10% as hazardous waste (ISDD), and 10% as ISDD with stabilization. To address areas inaccessible to excavation, in situ thermal desorption was implemented. The groundwater had to be lowered 1 m in a large portion of the thermally treated area at a continuous flowrate of 265 m3/h using 12 specific vessels (successions of activated carbon treated with sulfur and ion exchange resins) to allow temperatures to rise to the 250-350°C needed for adequate volatile Hg removal. Treatment began in November 2017, aiming for completion in summer 2018. Soil vapors were collected and treated in a unit that first cooled the vapors to 12°C to allow the liquids to condense for recovery, including liquid Hg. The non-condensables (including Hg) were then polished through sulfur-coated activated carbon vessels before release to the atmosphere. Results show high efficiency of Hg removal from the soil with efficient collection in the vapor treatment system. The site is permanently monitored for Hg vapors to ensure public safety.
Longer abstract: https://haemers-technologies.com/wp-content/uploads/2018/03/Intersol2018_TechnicalResume_sensitivesite_mercury.pdf
Slides: https://www.intersol.fr/download/27032018/download.php?f=Intersol_2018_3-Jeremie_Leplat_Biogenie_Europe.pdf



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