United States

Environmental Protection

Aaencv

EPA/540/F-95/509

August 1995

&EPA

SUPERFUND INNOVATIVE

TECHNOLOGY EVALUATION

Emerging Technology Bulletin

Process for the Treatment of Volatile Organic Carbon and

Heavy-Metal-Contaminated Soil

International Technology Corporation

Technological Description: The batch steam distillation and

metal extraction treatment process is a two-stage system that

treats soils contaminated with organics and inorganics. This system uses conventional, readily available process equipment, and

does not produce hazardous combustion products. Hazardous

materials are separated from soils as concentrates, which can

then be disposed of or recycled. The treated soil can be returned

to the site.

During treatment, waste soil is slurried in water and heated to

100 degrees Celsius. This heat vaporizes volatile organic compounds (VOC) and produces an amount of steam equal to 5 to

10 percent of the slurry volume. Resulting vapors are condensed

and decanted to separate organic contaminants from the aqueous phase. Condensed water from this step can be recycled

through the system after further treatment to remove soluble

organics. The soil is then transferred as a slurry to the metals

extraction step.

In the metals extraction step, the soil slurry is washed with

hydrochloric acid. Subsequent countercurrent batch washing with

water removes residual acid from the soil. The solids are then

separated from the final wash solution by gravimetric sedimentation. Most heavy metals are converted to chloride salts in this

step. The acid extract stream is then routed to a batch distillation

system, where excess hydrochloric acid is recovered (see figure

below). Bottoms from the still, which contain heavy metals, are

precipitated as hydroxide salts and drawn off as a sludge for

offsite disposal or recovery.

As a batch process, this treatment technology is targeted at sites

with less than 5,000 tons of soil requiring treatment. Processing

Recycle water from

extraction step

Contaminated soil

Offsite disposal

Steam

stripper

To recycle wafer

zjEx?Eo;esse, /l$--

Batch distillation vessel

Figure 1. Batch steam distillation step.

@ Printed on Recycled Paper
time depends on equipment size and batch cycle times; roughly been completed on three soils, for a total of nine tests. The

one batch of soil can be treated every four hours. Estimated removal rates for benzene, toluene, ethylbenzene, and xylene

treatment costs per ton, including capital recovery, for the two were greater than 99 percent. The removal rates for chlorinated

treatment steps are as follows: solvents ranged from 97 percent to 99 percent.

Batch Steam Distillation One acid extraction and two water washes resulted in a 95

percent removal rate for heavy metals. Toxicity characteristic

leaching procedure tests on the treated soils showed that soils

from eight of the nine tests met leachate criteria. Data were also

collected on the recovery rate for excess acid and the removal

rate for precipitation of heavy metals into a concentrate.

500-ton site

2,500-ton site

$299-393lton

$266-350/ton

Metals Extraction

(including acid recovery)

500-ton site

2,500-ton site

$447-619/ton

$396-545/ton

Waste Applicability: This process may be applied to soils and

sludges contaminated with organics, inorganics, and heavy metals.

Results: The batch steam distillation and metal extraction process was accepted into the SITE Emerging Technology Program

in January 1988. Under the program, three pilot-scale tests have

For Further Information:

EPA Project Manager:

Ronald Lewis

U.S. EPA

National Risk Management Research Laboratory

26 West Martin Luther King Drive

Cincinnati, OH 45268

513-569-7856

Fax: 513-569-7620

United States

Environmental Protection Agency

National Risk Management Research Laboratory (G-72)

Cincinnati, OH 45268

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

Official Business

Penalty for Private Use

$300

EPA/540/F-95/509