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Treatment of Petroleum-Contaminated Soils

Treatment Options (continued)

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Incineration

Incineration has been successfully used to treat soils contaminated with chlorinated hydrocarbons, dioxins, polychlorinated biphenyls (PCBs), and petroleum products. The main goal of incineration is to heat the contaminated media to temperatures between 870 and 1,200 °C, volatilizing and burning halogenated organic compounds and other compounds that are difficult to remove. The operating temperature of a typical incinerator is well within the boiling point of compounds found in petroleum (table 6). Because of these high temperatures, no materials requiring special disposal considerations are produced when petroleum-contaminated soils are incinerated. The four main types of incinerators are: circulating bed combustors, fluidized bed incinerators, infrared combustion incinerators, and rotary kilns.

Contaminated soils can be incinerated onsite or the excavated soil can be transported to an incinerator offsite. Companies that offer onsite incineration usually provide a service that includes rental of the incinerator and a crew (two people per shift) to operate the incinerator. The incinerator is shipped to the site in several different trailer loads. The estimated shipping weight is at least 40,000 pounds. Some type of foundation will probably be required. Typical foundations are gravel pads, concrete, skids, and sheet piles. The foundation is usually 50 feet wide by 100 feet long. An 8- by 20-foot trailer will be required for the controls. The incinerator requires fuel (usually diesel) for combustion and three-phase electrical power. Fuel consumption is estimated at 10 gallons of fuel per ton of soil when the soil has a water content of 10 percent. Several gallons of water per minute are required for cooling and dust suppression. Logs and other large items are removed before the soil is loaded into the incinerator. Incineration takes about 1 hour for every 5 to 10 tons of petroleum-contaminated soil. The incinerator's exhaust gas is clean. The treated soil can be used as fill material.

Use in Cold, Wet, Remote Regions

Other than the problem of excavating frozen soils, experience with incineration has been mostly favorable in cold regions. According to vendors contacted for this study, the only operational problem encountered has been freezing of the cooling tower.

Incineration of contaminated soil works best for soils with low water content. This requirement may present challenges when treating contaminated soils in regions with high precipitation. The ideal ratio of soil-water to soil mass for soils to be incinerated is 1:10 (information provided by General Atomics, appendix C). Excavated soil can be covered to help keep it dry.

Incineration requires barge or road access to the work site. You should plan for an extended stay at the site when using this treatment.

Incineration has been used in Alaska on the Kenai Peninsula for soils contaminated with PCBs. The majority of this work was performed in the late 1980s and early 1990s. Diesel-contaminated soil was also successfully treated by incineration at Kotzebue and Kenai, AK (information provided by General Atomics, appendix C). While these sites are not considered remote, the successful treatment of contaminated soil does indicate that incineration is a viable treatment system for cold, wet regions.

Cost Estimate

The majority of the cost for incineration will probably be in shipping and renting the incinerator. Costs associated with excavation of the soil have been discussed previously. Table 9 provides additional items to be included in a cost estimate for incineration. Assumptions include:

Table 9—Items to be included in a cost estimate for incineration of contaminated soil.
Cost estimating factors
Mobilization and demobilization.
Incinerator.
Incinerator shipping.
Service cost.
Diesel for the incinerator—Estimated fuel consumption is 10 gallons per ton of soil.
Fuel for the generator—Estimated fuel consumption is one-half gallon per hour.
Fuel for the backhoe—Estimated fuel consumption is 2.6 gallons per hour.
Foundation—Estimated material volume required for foundation is 30 cubic yards (2-inch-thick foundation).
Confirmation sampling—The number of samples depends on the size of the contaminated site and on the regulatory agency.
Accommodations for extended stay.

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