Southeast Rockford Groundwater Contamination Superfund Project

Catalytic Oxidation

Southeast Rockford Groundwater Contamination Superfund Project

February 2001

Background. The contaminants of concern in the Southeast Rockford Groundwater Contamination Superfund Project are mainly industrial solvents in a class of chemicals called volatile organic compounds (VOCs). "Volatile" means that they are readily converted to gas (vapor). "Organic" means they contain carbon. The Illinois Environmental Protection Agency (Illinois EPA) and the U.S. Environmental Protection Agency (U.S.EPA) are proposing catalytic oxidation as a method of treating VOC vapors in Source Areas 7 and 11 of the Southeast Rockford Groundwater Contamination Superfund Project.

What is catalytic oxidation? Catalytic oxidation is a method of breaking VOC compounds into harmless substances of water and carbon dioxide plus hydrochloric acid. The hydrochloric acid is directed to a scrubber where it is treated. (See diagram below).

What is a catalyst? A catalyst is a substance that increases the rate of a chemical reaction. In this case, the catalyst will probably be a precious metal such as platinum or palladium. The catalyst causes VOCs to be destroyed at a lower temperature than would be necessary without the catalyst.

What is oxidation? Oxidation, in this case, is the union of a substance with oxygen. Rusting of iron and burning of firewood are two examples of this type of oxidation. When the VOC vapors are preheated to at least 890° F and placed in the presence of a catalyst, oxidation occurs; that is, the carbon in the VOCs unites with oxygen creating carbon dioxide, and the hydrogen unites with oxygen creating water. Carbon dioxide is a major component of the air we exhale and is a harmless substance.

What is the catalytic oxidation process? (See diagram above). VOCs from the contaminated soil and water beneath the ground vaporize (evaporate) into the air pockets beneath ground surface and above the water table. A collection system collects these vapors. As VOC vapors are collected, more VOCs vaporize from the contaminated soil and water into the air pockets, thus reducing the amount of contaminants in the soil and water. After the vapors are collected, they are directed into a module that separates the water out of the vapor. The VOC vapor is sent to a burner where it is preheated to at least 890° F before being directed into the catalyst module where a reaction takes place that breaks the VOCs apart. The newly formed compounds (water, carbon dioxide and hydrochloric acid) leave the catalyst module and go into the scrubber where the acid is neutralized.

How is the hydrochloric acid neutralized? The hydrochloric acid is treated in the scrubber with a substance such as calcium carbonate, which reacts with the acid, forming water and salt. Water would be discharged from the scrubber into a nearby drainage ditch. The water would meet all state and federal water quality requirements for discharge.

What air emissions come out of the treatment system? Carbon dioxide and water are the primary compounds released to the air from the system.

Can other compounds of concern be created when the vapors are heated? It is highly unlikely that other compounds of concern, such as dioxin, can be created in this system. Dioxin creation in similar systems requires specific conditions including the presence of materials such as rust (iron oxide) or fly ash. These materials provide a place for chemicals to accumulate where they can be close enough to one another that the chemical reactions creating dioxins can occur. There would be no rust in this system since the entire system would be constructed of stainless steel. There would be no fly ash since only vapors, not soil, are being treated. In any event, if catalytic oxidation were chosen, the Illinois EPA would carefully regulate and closely monitor the unit to ensure that it meets all state and federal requirements for environmental protection. The agency also would take other precautionary measures, described below, to ensure that the unit is operated safely.

What laws and regulations would the unit be required to meet? The catalytic oxidation unit would be required to meet the substantive requirements of all state and federal laws and regulations for such a unit, but no actual permits would be issued since the unit is being operated on a federal Superfund site. Federal and state requirements include those of:

• The Clean Air Act, which regulates emissions into the air.
• The National Pollutant Discharge Elimination System (NPDES), which regulates discharges into the waters of the state.

How would the Illinois EPA ensure that these and other safety requirements are met?

• Proof of performance test before regular operations. Before regular operations begin, the unit would be required to pass a proof of performance test. Tests conducted during the proof of performance would include tests of:
  • Air emissions for site-related hazardous air pollutants, total volatile organic compounds, carbon monoxide, dioxins and hydrochloric acid. For some of these parameters, such as dioxins and hazardous air pollutants, samples of air emissions from the stack would be collected and sent to a laboratory for analysis. The unit would be shut down until laboratory results are available showing that emission standards were met.
    
    There are no federal or Illinois standards regulating the release of dioxins from catalytic oxidation units. However, U. S EPA has established a dioxin standard for incinerators that burn hazardous waste commercially. . If catalytic oxidation were chosen for Areas 7 and 11, the Illinois EPA and U.S.EPA would require the catalytic oxidation unit to meet this stringent standard. This standard is 0.20 nanograms per dry standard cubic meter of air (air with moisture removed). A nanogram is 1 billionth (0.000000001) of a gram and a gram is approximately 4 hundredths (0.04) of an ounce.¹
  • Operating conditions such as temperature of the vapors as they enter and exit the catalyst module, flow rate, and other parameters that can be monitored in real time. Real time monitoring means the monitoring results are available immediately

¹The air and soil in Rockford may already contain small amounts of dioxins. Industrial and residential activities (such as burning plastic) provide conditions suitable for the creation of dioxins. . If dioxins were detected in the air emissions from the catalytic oxidation unit, it would be difficult to tell whether the unit created the dioxins or if the dioxins were already present in the air or soil before the catalytic oxidation unit began operation. In any event, the Illinois EPA and U.S. EPA would require that the unit meet the strict air emission standards discussed above.

• Continuous monitoring during regular operations.. During regular operations, real time monitoring for parameters such as temperature, and flow rate would be conducted to make sure that the unit is meeting the same conditions as it did during a successful proof of performance test.
• Automatic shut down of the feed. The system will be equipped with a mechanism that will shut down the unit if it fails to meet requirements. For example, if the control panel loses electrical power, if there is loss of proper air flow or loss of flame, or if temperatures or fuel pressure are not in the required ranges, the system will automatically shut down.
• Monitoring of water discharged to the drainage ditch. The water from the scrubbers in Area 7 and Area 11 would be discharged to nearby drainage ditches and would be monitored to make sure it meets NPDES requirements. Specifically, the water would be monitored to make sure it is not acidic. In Area 7, the water from the water/vapor separator would also be discharged to a ditch and monitored to make sure it meets all NPDES requirements. In Area 11, water from the water/vapor separator would be hauled off-site for proper disposal.

Why are Illinois EPA and U.S. EPA proposing catalytic oxidation? Due to the concentration of VOCs, vapors removed from soils and groundwater at Areas 7 and 11 would require treatment before being released into the atmosphere. A common method used to treat VOC vapors is to pass the vapors through granular activated carbon (similar to charcoal). However, the concentrations of the vapors in Areas 7 and 11 (especially during the early part of the remediation) would be too high for carbon treatment. The vapors could also be incinerated at high temperatures without a catalyst. However, incineration systems are more expensive to build and require more fuel and energy to operate.

The catalytic oxidation unit provides a good balance between effective treatment and cost. Catalytic oxidizers are commonly used for this type of remediation.

Who would own and operate the treatment system? Illinois EPA and U.S.EPA would oversee the operation of the treatment facility. Depending on cost efficiency, federal and state funds would be used to either purchase the treatment systems or lease them for the duration of the projects.

What would the treatment unit look like and where would it be located? At Area 7 (Ekberg Park) the treatment unit would be housed in two small buildings that would look similar to a two-car garage and a tool shed. The larger building would have a stack approximately 20 feet tall and 16 inches in diameter. The Area 7 fact sheet contains a figure that shows the location of the two buildings. Both buildings would be slightly northwest of the existing facilities within the park.

At Area 11, one building that would look similar to a two-car garage would house the treatment system. The stack at Area 11 would also be approximately 20 feet tall. The Area 11 fact sheet contains a figure that shows the location of the treatment building. The treatment building is planned to be located near the southwest corner of the building occupied by Rohr Manufacturing building.

How long would the treatment unit operate? There are many factors, such as flow rate of air beneath ground surface, that are difficult to predict, making it impossible to give a precise length of time needed for treatment. In Area 7, the catalytic oxidation unit is expected to operate for approximately 10 years-the length of time that soil vapor extraction is anticipated to take. Although soil vapor extraction in Area 7 is expected to be completed in 10 years, it should be noted that leachate in Area 7 would probably need to be pumped and treated for an additional twenty years. After the catalytic oxidation unit is shut off, the vapors from the leachate would be treated by passing them through granular activated carbon. The granular activated carbon removes the VOCs.

At Area 11, the treatment unit is expected to operate from two to five years. However, the presence of buildings in the area complicated the investigation, and project personnel are unsure how long treatment may be required at Area 11. Illinois EPA would make a firmer estimation of the length of time needed for treatment after additional data are gathered during the design phase of the system.

Would operations create odors or noise? Noise is not expected to be a problem since the treatment units would be inside a building. Odor is not expected to be a problem since the primary air emissions would be carbon dioxide and water.

For More Information:

Contacts: For more information about the project including fact sheets on the remedial investigation results, feasibility studies and proposed plans for each of the four major source areas, you may contact the Illinois EPA staff listed below:

Repositories: Full reports for the project may be reviewed at the following locations.

Administrative record file: The administrative record file is located at the Illinois EPA headquarters in Springfield, Illinois. Call 217/782-9878 for an appointment. The administrative record file will also be located on microfiche at the Main Branch of the Rockford Public Library at 215 N. Wyman in Rockford.