Science for Superfund Lawyers

Melvyn Kopstein

Editors' Summary: Cleaning up hazardous waste often involves complicated questions of law, science, and engineering, all intertwined. Yet, too often professionals of each discipline do not talk to one another, or fail to understand central concepts in each other's fields. To be successful, environmental lawyers are called upon to be not only experts on the law, but also generalists on the scientific and engineering issues involved in cleaning up hazardous waste.

In this Article, the author, a chemical engineer, surveys the technologies available to clean up hazardous waste. He outlines the kinds of contamination the various technologies are suited for and how they can mesh into an overall cleanup plan. He concludes by noting that lawyers who understand the technology available can often act affirmatively to get hazardous waste sites cleaned up, improving environmental quality and saving their clients' money at the same time.

Melvyn J. Kopstein is a Rockville, Maryland, chemical engineer who consults extensively on hazardous waste litigation and environmental toxic torts, and represents lenders and developers in environmental matters. Dr. Kopstein graduated with honors from Drexel University and received his M.S. and Ph.D. degrees from the University of Pennsylvania.

[19 ELR 10388]

The practice of environmental law encompasses an expanding array of complex scientific and regulatory disputes. To properly represent a client's interests, the environmental attorney must sometimes wear an "engineer's hat." He or she must understand and know how to obtain answers to questions such as:

1. Will a particular technology, or set of technologies, work effectively on wastes at a client's site?

2. Were all feasible alternatives, including no action, properly considered in the record of decision?

3. Did the remedial investigation look for sources of contamination other than the client site? For example, in a heavily industrialized area, is it certain that no additional parties are responsible for contamination?

4. Are cleanup goals set forth in a record of decision consistent with health and environmental risks?

5. When does it make sense to advise a client to "get the jump" on enforcement agencies by taking a proactive approach to cleanup?

This Article provides an easy-to-understand snapshot of existing technologies for the treatment of hazardous wastes. The Article goes on to show why responsible parties may want to seize the initiative from enforcement agencies and clean up hazardous waste sites before enforcement action is brought.

Background

In the United States, over 300 million tons of hazardous waste is generated annually.¹ Nationally, more than 30,000 sites are potentially contaminated by hazardous chemicals.² These locations are included in the CERCLA Information System (CERCLIS), the Environmental Protection Agency's (EPA's) hazardous waste site computerized data base.³

Hazardous chemicals can spread and pose dangers to the public health and environment in several ways. For example, they can be leached and drawn off to contaminate streams, lakes, or groundwater. The air can be contaminated when volatile organic compounds and other liquids evaporate or undergo reactions. Metals and organic solvents can damage vegetation, endanger wildlife, and poison drinking water supplies.

Thus, the formulating hazardous waste site cleanup plan is analogous to designing a complex chemical engineering process. Because no two site cleanups are alike, there is uncertainty in extrapolating the results from previous cleanups or pilot tests involving a given technology to the site in question. The fact that a technique for treating one type of waste is effective under the controlled conditions of a pilot test, or under the now well understood conditions [19 ELR 10389] of an earlier cleanup, does not guarantee success in a new and completely different set of circumstances. Before that particular waste treatment method is employed at a new site, the known differences (involving the waste and site characteristics) between the previously treated site and the present one must be analyzed.

Land Disposal

Land disposal was the most common method of managing contaminated sites in 1980 when the Comprehensive Environmental Response, Compensation, and Liability Act⁴ (CERCLA or Superfund) was enacted. In land disposal, untreated hazardous chemicals are placed in pits, landfills, or surface impoundments, typically with linings, clay caps, and a monitoring system to detect leaks.

EPA has taken regulatory steps to make it more difficult to dispose of hazardous wastes in this way. For instance, in considering a landfill disposal permit application, the Agency assumes that such landfills are saturated by an aquifer. Furthermore, the landfill is assumed to be a prescribed distance up-gradient from a receptor well. By "back calculating" a maximum allowed leachate concentration from a presumed concentration of hazardous chemicals at the receptor well (based on drinking water standards), EPA determines whether the hazardous waste may be disposed of in the landfill. In fact, however, few landfills have aquifers passing through them. There is almost always an unsaturated zone between the landfill and an aquifer. This attenuates the concentration of hazardous chemicals before they enter an aquifer. But by assuming the worst case scenario, EPA is discouraging the disposal of untreated hazardous chemicals in landfills.

Land disposal amounts to a relatively inexpensive but essentially short-term solution. Leaks and other environmental defects can result in longer term environmental problems that may be difficult to diagnose and very expensive to correct. CERCLA § 121 requires EPA to prefer remedial actions that first treat hazardous wastes to reduce their volume, toxicity, or mobility.⁵ EPA is to encourage the development and implementation of innovative waste treatment technologies.⁶

At least partly in response to such legal prodding, techniques for treating wastes rather than merely land disposing them have developed rapidly in the 1980s. Modern treatment techniques fall into five categories: thermal treatment, immobilization, physical treatment, chemical treatment, and biological treatment.

Thermal Treatment

Thermal treatment is the high temperature reaction of hazardous chemicals in the waste mix. The goal of technologies which belong to this category is to detoxify as much of the hazardous waste as possible, usually by turning the waste into something that is not hazardous. Effectiveness of thermal treatment is expressed in terms of having a destruction and removal efficiency (DRE) that exceeds 99.99 percent. Other advantages can include volume reduction and energy recovery.

At the same time, indiscriminate and complete thermal treatment of all chemicals at a site can be very costly and is not necessarily desirable. In fact, undesirable by-product residues can result if the technology, reaction conditions, and hazardous waste mixture are incompatible. For example, hydrogen chloride and particulates are often residual by-products of thermal treatment.

Waste that is to be thermally treated is either removed from the Superfund site or prepared for on-site mobile treatment. Because of the growing number of sites, greater use will be made of mobile thermal treatment systems in the future.

There are many types of thermal treatment technologies, in various stages of development, that may be employed on different types of hazardous waste.

Incinerators

Basically, incinerators are specialized furnaces. Waste and air are mixed and then burned in the furnace, with carefully controlled air flow. Incinerator types include fluidized bed incinerators, rotary kiln incinerators, infrared incinerators, and pyrolytic incinerators.

Fluidized bed incinerators are furnaces lined with heat-resistant material and containing a "bed" of inert granular material such as silica sand. If contaminated soil is being treated, then the soil itself can serve as the bed material. Air needed for combustion is injected upward from the bottom of the furnace, at a speed fast enough to expand and suspend the bed material. The minimum air velocity refers to the air speed needed to cause the bed to expand. The maximum velocity is the speed above which the bed is "entrained," that is, carried over with the product gases. The design velocity will be somewhere between the minimum and maximum values, and will depend on factors such as desired residence time and temperature.

Fluidized bed incinerators and a "first cousin" variation known as circulating bed combustors (these use higher air velocities and incorporate circulating solids) attain high degrees of mixing. They are very efficient and can be operated at lower temperatures than other incinerators, thus generating fewer nitrogen oxides. Volatile metals emissions can be easily prevented, as can the emission of sulfur oxides, if limestone is included in the bed material. There is extensive operating experience for fluidized bed reactors in applications such as coal gasification, coal combustion, refinery cooking, and chemical processing.

Fluidized bed incinerators are very "forgiving" about the physical condition of wastes that are acceptable, and have minimal auxiliary fuel requirements. Many types of wastes may be processed as solids, sludges, slurries, and liquids. For example, these wastes can include contaminated soils, halogenated and non-halogenated organics, polychlorinated biphenyls (PCBs), and pharmaceutical and phenolic wastes.

Even so, fluidized bed incinerators cannot handle oversized wastes that cannot be reduced to the necessary size for processing, nor can they handle high sodium and heavy metal waste constituents. A few types of wastes, such as low melting points chemicals, can cause operational difficulties. There is only limited commercial experience in [19 ELR 10390] using fluidized bed incinerators in the treatment of hazardous wastes.

Rotary kiln incinerators have been used for many decades to burn ordinary trash. As the most common type of incinerator, rotary kilns differ from fluidized bed incinerators in the way air and waste are mixed for combustion. Rotary kilns employ a grate or rotating kiln to effect mixing. Mechanical feeding arrangements such as screw feeders, moving grates, and special hoppers are used. Auxiliary burners (oil or gas fired) are generally supplied to ensure ignition at all times. These incinerators require an "afterburner" (secondary combustion chamber) to complete the combustion of hazardous waste in the kiln exhaust gas. Before discharge to the atmosphere, the exhaust gas from the incinerator must be processed in an air pollution control unit (a "scrubber") to remove particulates and sulfur oxides.

Fluidized bed incinerators have more "built-ins" than rotary kiln incinerators. No afterburners or air pollution control units are necessary in fluidized bed incinerators. On the other hand, there is much more operating experience available for rotary kiln incinerators than for fluidized bed incinerators. Fixed and mobile units are widely available commercially from many vendors for treating a broad range of hazardous wastes. The only major incompatibility is volatile metals.

Infrared incinerators destroy hazardous wastes using infrared energy as the principal heat source. (Fluidized bed and rotary kiln incinerators use conventional fossil fuels as the main heat source.) For infrared incineration, hazardous wastes are fed into the furnace on a woven metal alloy conveyor belt. In the primary combustion chamber the wastes are exposed to infrared radiation for a prescribed period of time. Any remaining organics are carried on the conveyor belt to a secondary combustion chamber that is either propane-fired or contains additional infrared heating elements. As with rotary kiln incinerators, the exhaust gases from the secondary combustion chamber must pass through an air pollution control unit before being discharged to the atmosphere.

There is limited commercial operating experience in the use of infrared incinerators to treat halogenated and non-halogenated organics (including PCBs), contaminated soils, dioxins, and spent activated carbon. In addition to an incompatibility with volatile metals, infrared incinerators require process waste feedstocks that are at least 22 percent solids, and there are size restrictions for solids that cannot be ground or shredded.

Pyrolytic incinerators destroy organic wastes without using oxygen. Oxygen is excluded to allow the incoming waste to be separated in a primary chamber into gaseous organic and inorganic fractions. The secondary combustion chamber is hot enough to reduce organic compounds to harmless gases and water vapor. The inorganic fraction is in the form of a "char," which must be disposed of. This technology is being developed to treat wastes that are in the form of drummed liquids, sludges, and soils with both low and high heating values, but commercial experience is still limited.

Wet Air Oxidation

The thermal treatment methods described so far are incinerators that involve waste breakdown in air. Wet air oxidation breaks down dissolved organic and oxidizable inorganic materials in a high temperature, high pressure wet environment. Wet air oxidation has found commercial applications in small scale power generation, biological wastewater sludge treatment, coal processing to increase fuel density, and some biological processes. While not yet been shown effective for hazardous wastes on a commercial scale, it may have the potential to treat a variety of liquid and solid wastes that can be oxidized. But even then, wet air oxidation will generate gaseous, liquid, and solid effluents and further treatment may be required to remove toxic or other undesirable constituents from these effluents.

Immobilization

Immobilization is the process of adding materials that combine with wastes either chemically or physically, or both, to keep it from moving into groundwater or other places that it can cause harm. Immobilization can be "in situ," meaning directly at the site where the waste is found. Alternatively, the waste can be excavated and its liquid portion immobilized prior to disposal in a landfill. Or, excavation and complete immobilization converts all of the wastes into a solid mass. Generally, in situ immobilization is least expensive, and excavation with complete immobilization is most expensive. All three methods have been applied commercially.

In situ vitrification is a different type of immobilization. Wastes, soils, and sludges are melted at high temperatures through the use of electric current. The molten mixture is cooled to form a glassy solid.

Stabilization, fixation, and solidification are terms that are often used to describe immobilization. Technologies for immobilization are useful in treating metals, asbestos, radioactive materials, inorganic corrosives, and inorganic cyanides.

Typically, fly ash, asphalt, cement, and similar materials are mixed with the wastes to immobilize them. Fixation and stabilization materials, as well as additives, are considered proprietary by vendors.

Immobilization technologies are highly mobile and adaptable to a fairly wide range of wastes, but the success of immobilization depends on the exact hazardous waste mix. Accordingly, it is necessary to test representative waste samples as well as the chemical and physical properties of the immobilized waste product. This screening is generally performed by vendors at the bench or pilot plant scales of testing. For example, cement-based immobilization is usually not suitable for fine particulates, wastes that are 40 percent liquid, sulfates, or soluble metal salts.

Physical Treatment

Essentially, physical waste treatment processes separate wastes into two or more streams. This can be quite useful in managing hazardous waste mixes with constituents that are incompatible. Ideally, the remediation would be designed so that each waste stream produced could then be treated effectively by another process, such as incineration or immobilization.

Air stripping transfers volatile organic contaminants (VOCs) from a dilute water solution to air. Applications include removing VOCs, such as benzene, that occur in small but objectionable levels, from groundwater and waste [19 ELR 10391] water. A modification of air stripping is being used for treating contaminated soils; in this technique, a vacuum is applied to pull air (along with VOCs) through the soil. The VOC-laden air must then be treated before it is released.

In mechanical aeration/extraction, volatile contaminants such as benzene, toluene, xylene, halogenated VOCs, ketones, and alcohols are removed from soil that has been heated. Heating accelerates the transfer of the contaminants from soil to air. The soil is aerated through devices such as mechanical rototillers, on-site vacuum extractors, and pneumatic conveyors. Mobile treatment systems are commercially available for this process.

Activated carbon adsorption is a widely commercialized, mobile process in which soluble contaminants are collected on the surface of activated carbon. It is one of the most frequently used techniques for removing traces of organic compounds (such as VOCs and organometallic compounds) from water. EPA has an activated carbon adsorption emergency response unit known as the "Blue Magoo" that has operated at dozens of sites.

Soil washing extracts hazardous chemicals (such as concentrated organics and heavy metal compounds) from sludges and soils by washing them with a liquid such as water, organic solvents, and acids and bases. The contaminants to be removed determine the nature of the washing fluid. The soil or sludge may be excavated before washing, or the process may be performed on site. The "spent" washing fluid has to be cleaned to remove and destroy the hazardous constituents. Other treatment derived wastes also have to be treated or disposed of in a landfill. Two mobile soil washing systems are available commercially.

In situ soil flushing consists of a groundwater extraction and reinjection system that is applied to soils without excavation. Extraction wells are drilled into the groundwater in the contaminated soils zone, and reinjection wells are drilled into the groundwater up-gradient from the site. A chemical agent is injected to greatly accelerate VOC, arsenic, selenium, soluble organic, and other contaminants leaching from permeable soils. The contaminated groundwater is extracted, treated, and reinjected in the up-gradient wells to complete the process "loop." Mobile units are now commercially available for this process.

Filtration is used to de-water soils and sludges, and to remove suspended solids from a fluid. Vacuum, pressure, and gravity filters are used for dewatering, while granular filters remove solids. Many vendors offer commercial filtration in stand-alone mobile units (which must be integrated with other equipment to complete the waste treatment system), or as part of a total treatment system.

Membrane separation uses semi-permeable membranes to allow certain chemicals to pass through while rejecting others. The membranes act as "screens" based on pore size, ion valence, and similar properties. A mobile unit can be used to treat water with metal wastes and groundwater containing PCBs, chlorinated organics, insecticides, and other compounds.

Phase separation applies physical force to remove toxic constituents suspended incontaminated water, and is based on the differences in specific gravities. The process works only for wastes that are suspended in water, not waste that are actually dissolved. For example, several processes are available to treat oil-water mixtures, solid suspensions, and hydrophobic (i.e. repelled by water) chemicals. The oily wastes that are recovered may be treated further or recycled for use as a solvent or fuel. There are many commercial mobile phase separation units available.

Chemical Treatment

Chemical treatment can change the chemical makeup of a waste so that it is no longer hazardous. Alternatively, it can be a pretreatment step to make it easier to manage complex hazardous waste mixes. The products of such chemical treatment generally require further processing, such as incineration, immobilization, and disposal, as part of a complete remediation process.

Chemical reduction-oxidation (REDOX) treatment reduces the toxicity of many organic and heavy metal compounds. REDOX reactions (so named because they involve the reduction and oxidation of chemical compounds) are used to combine comparatively unstable compounds into nonhazardous compounds. REDOX treatment is tailored to the characteristic waste by selecting appropriate chemical additives and controlling the acidity of the reacting mixture. Rapid mixing is maintained in a setup that resembles a continuous stirred tank reactor (CSTR) from the chemical industry. In a CSTR, the concentration of each chemical is uniform throughout the reactor, as is the temperature. The product slurry must be processed by another treatment method such as chemical precipitation. REDOX treatment is commonly used on a commercial scale to treat hazardous wastes now being generated, and probably has important potential in the treatment of CERCLA wastes with hazardous constituents such as benzene, phenols, cyanides, arsenic, iron, chromium, mercury, and lead.

Neutralization moderates the pH of a hazardous waste solution to a range of 5 to 9. Solutions with a pH lower than 5 are very acidic, and those with a pH greater than 9 are very caustic or "basic." The range between 5 and 9 is mildly acidic (pH of 5 to 7) or mildly caustic (pH of 7 to 9). Pure water has a neutral pH of exactly 7.

Sodium hydroxide (strong base), sulfuric acid (strong acid), and lime (a buffer used to maintain pH in the desired range) are the most common reagents in CERCLA waste neutralization. As in the REDOX system, the waste is mixed with reagents in a CSTR. In addition to liquids, neutralization can also be used on sludges and slurries that contain a variety of organic and inorganic hazardous wastes. Commercial scale fixed and mobile neutralization units are available, but in most cases, neutralization comprises only part of the total CERCLA waste treatment process.

Precipitation is almost always used in concert with flocculation and sedimentation for wastewater containing heavy metals and suspended solids. In precipitation, a chemical is added to combine with a dissolved waste and form a solid that drops out of the solution. Flocculation uses chemicals to transform small suspended particles into larger particles that will settle at the bottom of a tank. In sedimentation, gravity causes small suspended particles to settle to the bottom of a tank. The sludges that are produced in these processes must be collected and disposed of after further treatment.

Chemical extraction separates contaminated sludges and [19 ELR 10392] soils into their organic, liquid, and solid fractions. The liquid and organic fractions are separated by a solvent that preferentially dissolves one or more compounds of a mixture. The solid fraction can be obtained by crystallization or evaporation. Sludges and soils which contain halogenated semivolatiles, nonhalogenated semivolatiles, and PCBs are candidates for treatment by chemical extraction.

In situ chemical treatment is applied to contaminated soils and wastes in place. Depending on the hazardous waste mix, a wide range of chemical reagents (such as solvents, precipitating and neutralization agents, and stabilizers) can be used. The exact mix of chemicals and conditions of their use is custom engineered to the site's needs. Treatment can be designed with several techniques in combination. In situ chemical treatment has been used commercially at modern manufacturing sites, but not yet at Superfund sites.

Biological Treatment

Bioremediation involves the use of microorganisms to render potentially toxic materials harmless. The microorganisms can either be aerobic (requiring oxygen) or anaerobic (not requiring oxygen).

In situ bioremediation uses bacteria to digest organic compounds in soils. It can significantly reduce levels of organic contaminants in soils, and is less expensive than soil excavation. It can be effective in treating solvents and chlorinated aromatic compounds, and for removing gasoline and diesel fuel from soils. Thus, it is a candidate for cleaning up leaks from petroleum underground storage tanks. Bioremediation employs many types of microorganisms, and there is usually no attempt to select particular bacteria or genes for stimulation. Bioremediation can be refined by a procedure known as genetic ecology, which identifies specific toxin-destroying genes, stimulates their growth, and tests their effectiveness on contaminated soil samples.

Aerobic and anaerobic biological treatment for Superfund wastes are adapted from conventional activated sludge processes. They treat contaminated wastewater containing phenols, formaldehyde, diesel fuel, and many nonhalogenated organics. Biomass sludges result from both aerobic and anaerobic treatment systems, and require further treatment.

Slurry phase treatment decontaminates contaminated soils and sludges in mobile bioreactors. It can be used in a system where soil washing precedes the biological step to remove volatile and non-volatile metallic compounds. A wet slurry is prepared and mixed with the selected microorganisms to biodegrade target contaminants. Several commercial size units are available.

Solid-phase treatment uses conventional soil management techniques to maintain desired permeability, temperature, and moisture level to accelerate the biodegradation of contaminants. Commercial units are available to treat soils that contain pesticides and petroleum distillates.

Innovative Technology

The 1986 amendments to CERCLA direct EPA to encourage the research, development, and demonstration of new treatment technologies. EPA's Office of Solid Waste and Emergency Response established the Superfund Innovative Technology Evaluation (SITE) program in 1986 in order to gather cost and performance data for emerging treatment technologies. These data are critical in evaluating the risk of scaling up a technology from pilot plant to commercial size. By the end of 1988, seven field demonstrations were completed under the SITE program.

Innovative technologies are being developed in each of the five treatment categories. Improvements in existing methods will be related to mobility, adaptability to the wide range of conditions at Superfund sites, and compatibility with other methods. Biological remediation techniques are using genetic ecology and genetic engineering to generate natural and man-made microorganisms.

There may be techniques proposed that are not at all related to current practices and research. For example, peat is quite effective in removing heavy metals and organics from contaminated waters, and has been used in managing oil spills. Peat may find use in the cleanup of contaminated aquifers by serving as a metals filter, and in cleaning up liquid hazardous wastes.

Proactive Counsel

Given that EPA-managed Superfund cleanups take so long and cost so much, it may be worthwhile for potentially responsible parties to seize the initiative by performing their own analyses, and then proposing remedial actions that are technically and environmentally sound, and in compliance with EPA regulatory guidance. Chances are excellent that such remedies will also be more economical than solutions imposed by EPA and its contractors. In addition to being more economical than government imposed solutions, responsible party remedial actions that do not tax the limits of treatment technologies are likely to perform well.

1. ENVIRONMENTAL PROTECTION AGENCY, ENVIRONMENTAL PROGRESS AND CHALLENGES: EPA'S UPDATE 85 (Aug. 1988) (#EPA-230-07-88-033).

2. Id. at 93-94.

3. See Freedman, Proposed Amendments to the National Contingency Plan: Explanation and Analysis, 19 ELR 10103, 10114 (Mar. 1989).

4. Pub. L. 96-510, as amended, 42 U.S.C. §§ 9601-9675, ELR STAT. CERCLA 44001-44081.

5. 42 U.S.C. § 9621, ELR STAT. 44054.

6. CERCLA § 311, 42 U.S.C. § 9660, ELR STAT. CERCLA 44073.