NATO/CCMS Pilot Study Evaluation of Demonstrated and ... - CLU-IN

NATO/CCMS Pilot Project on Contaminated Land and Groundwater (Phase III) January 2001
The main aim and tasks of the pilot test was to solve the following problems in semi-industrial scale:
• to check recovery efficiency of the proposed gravity separation on 1 - 3 m 3 of polluted material;
• to check possible adsorption of Hg on clay minerals and its influence on the decontamination
efficiency;
• to test the dewatering of treated material;
• to specify the energy consumption and total costs of decontamination;
• to design the optimal decontamination unit that could be maintained and operated effectively
under the conditions of the local economy and infrastructure.
The Pilot Test was funded by the Czech National Property Fund. The total cost was 0.5 M CZK (13,000
USD).
3. TECHNICAL CONCEPT
The decontamination unit set up for the pilot test consists of the following devices:
• steel container—excavated material was loaded into steel container where the material was
blunged by
• hydromonitor—this device blunges and feeds the treated material to
• gravity storage bin—from this tank the suspended material was pumped to
• hydrocyclone—the first stage of separation - classifying into two fractions - mud and sand (in this
fraction, the metallic mercury is concentrated and the mud is dewatered and backfilled into the
excavation hole)
• centrifugal concentrator—the second stage of separation, the pre-concentrate is finally treated
• sedimentation basins—wastewater from hydrocyclone and centrifugal concentrator is pre-treated
(sedimentation of mud)
• centrifuge— dewatering of mud from hydrocyclone and sedimentation basins.
During the processing of polluted soil the important points of tested technology was sampled:
• polluted soil—this represents a problem because of the highly variable Hg concentration in the
material (due to occurrence of Hg in drops and/or finely disseminated), analyzed concentrations
vary from X00 to 120,000 ppm in the feed (i.e., polluted soil);
• waste from hydrocyclone (mud) —determined values of Hg concentration did not exceed 10
ppm;
• pre-concentrate from hydrocyclone (sandy fraction) —due to high specific weight of Hg it is also
complicated to collect representative samples;
• waste from centrifugal concentrator—due to high specific weight of Hg it is also complicated to
collect representative samples—determined Hg concentration was in order X ppm;
• concentrate, i.e., separated mercury—this output was not sampled because it is represented by
metallic mercury with admixture of sand, in frame of conducted Pilot Test about 9 ml of mercury
(i.e., approximately 121.5 g) was separated.
• process water—determined concentration of Hg were under the detection limit (