PubMed · 4240408
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1969. Five year forecast for contamination control.. https://pubmed.ncbi.nlm.nih.gov/4240408/
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A soil washing process is described in which high shear mixing, sprays, hydrosizing, flotation, and screening are integrated to countercurrently clean sand, silt and clay. Chemical techniques are summarized that can be used to remove selected contaminants from the soil and then clean the wash water for reuse. Descriptions of simple and complex processes, and a recent project are used to illustrate the points: (1) Soil washing is not a single process, but a collection of unit operations assembled for each project; (2) all process must be coordinated for the project to be successful; and (3) combining techniques in a few pieces of equipment debottlenecks soil washing.
The purpose of this work was to reduce soil volumes requiring aggressive treatment. A second purpose was to determine differences in separation due to distinct forms of the metal contamination and soil texture. The objectives were to apply hydroclassification and find mass and metal-contaminant distribution of four soils contaminated with heavy metals from firing ranges, a small arms incinerator, and an electroplating operation. The soils were slurried in water, sieved, and exposed to upward flowing water to separate the soil particles into four nominal size ranges. The popping furnace soil exhibited substantial lead among all particle size fractions. The firing range soils exhibited bimodal distributions. The electroplating soil exhibited a strong concentration of metals toward the <63 microm fraction. Attrition scrubbing moderately improved the enrichment of metals in several fractions. Extraction revealed the lead and chromium in the electroplating soil to be relatively immobile. These results suggest metal distributions are influenced by the different mechanisms of introduction into the soil. They also help to predict performance of processing options such as sieving hydroclassification and attrition scrubbing.
A soil treatability study was conducted using particle-size separation and soil washing to reduce the volume of material contaminated with polychlorinated biphenyls (PCBs) and lead at a Superfund site. Soil washing using surfactant was effective at removing 95% of PCBs into fine material and residual wash water. Results indicate that almost 80% of the material contaminated with up to 140 mg/kg PCBs could be treated to concentrations below 10 mg/kg using soil washing with surfactant. There did not appear to be a difference in lead removal using either particle size separation or soil washing, although the lead data have high uncertainty because of soil heterogeneity. Lead concentrations in soil were reduced from as high as 1700 to < or =150 mg/kg and from 560 to < or =220 mg/kg in about half of the material using particle size separation.