New York/ New Jersey Harbor: Alternative Methods for Ex ... - CLU-IN

water mixture is heated to 172 to 185°F, a span of temperatures which corresponds to the
range of boiling points of typical azeotrope solvent-water mixtures (2-8). As a result,
when the azeotrope is heated to these temperatures, it volatilizes. The azeotrope vapor is
then condensed into waste oil and a 2-layer liquid, which consists of a top layer of
solvent and an aqueous bottom layer. An oil polisher is used to remove the residual
solvent present in the waste oil. The polished waste oil is sent to an off-site facility to be
incinerated or disposed of in some other manner (Cardoni, interview). The solvent layer
of the azeotrope can be decanted off of the aqueous layer and used in the extraction
process. The water layer is drained from the vessel and is steam stripped to remove
residual solvents (Metcalf & Eddy, 2-9).
The wastewater layer is transported to a stripper column where any residual solvents are
removed by steam stripping. Organic compounds with lower boiling points can be
isolated by injecting steam into the sediment. Other organic compounds can be removed
from the wastewater or condensate by feeding water, just below the azeotropic boiling
point through the feed preheater. A portion of this feedwater vaporizes upon entering the
top of the column, and the remainder is stripped of residual solvents by upflowing steam
(2-10). The vapors produced by the stripping process are condensed and used again as
solvent in the extraction process.
The continuous solvent extraction process is identical to the batch solvent extraction
process, with a few modifications. The sediment must be screened to 1/8“ instead of
1/4“. Also, instead of periodically decanting the solvent and water azeotropic layer from
the sediment after extraction, the continuous process separates the two layers without
interruption during extraction. In the continuous process, the sediment is allowed to
escape through the bottom of the column, and the solvent is removed through the top of
the column. The solvent recovery, organic separation, and water stripping steps are the
same for both extraction processes.
The final step in the process, the SOLFIX solidification and stabilization step, involves
the addition of Portland cement to the sediment. As mentioned in The Process portion of
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