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DEMONSTRATION BULLETIN: THE BASIC EXTRACTIVE SLUDGE TREATMENT (B.E.S.T.) RESOURCES CONSERVATION COMPANY (RCC)
Citation:
Wagner*, T. DEMONSTRATION BULLETIN: THE BASIC EXTRACTIVE SLUDGE TREATMENT (B.E.S.T.) RESOURCES CONSERVATION COMPANY (RCC). U.S. Environmental Protection Agency, Washington, DC, EPA/540/MR-92/079, 1992.
Description:
The Basic Extractive Sludge Treatment (B.E.S.T.®) process is a solvent extraction system that separates organic contaminants from sludges, soils, and sediments. The primary distinguishing feature of the process is the extraction agent, triethylamine. The key to the success of triethylamine extraction is the property of inverse miscibility. At temperatures below 60°F, triethylamine is miscible with water; above 60°F, triethylamine and water are only slightly miscible. Therefore, by utilizing solvent chilled below 60°F, solids can be dewatered while simultaneously extracting organic contaminants. This is referred to as a cold extraction. Afterwards, the remaining organic contaminants can be removed at temperatures ranging from 70 to 1608°F and higher. These are referred to as warm and hot extractions, respectively.
The B.E.S.T.® process operates as follows. Contaminated material screened to less than 1/2 inch diameter (1/8 inch for this demonstration) is added to a refrigerated premix tank with a predetermined volume of 50 percent sodium hydroxide. After the tank is sealed and purged with nitrogen, chilled solvent is added. The chilled mixture is agitated, and then allowed to settle. After this cold extraction is completed, the resulting solution of solvated oil, water, and solvent is decanted from the solids and centrifuged. The solvent and water are removed from the solvent/water/oil mixture by evaporation and condensation of the solvent and water.
Cold extractions are repeated as additional feed is added to the premix tank so that enough solids are accumulated to warrant subsequent extraction cycles. Solids with high moisture contents may require more than one cold extraction. For this demonstration, a sediment containing 41% moisture required two cold extractions.
Once a sufficient volume of moisture-free solids is accumulated, it is transferred to a steam jacketed extractor/dryer. Warm triethylamine is added to the solids. The mixture is heated, agitated, settled, and decanted. This process can also be repeated. These warm and hot extractions result in separation of the organics not removed during the initial cold extraction.