450 H HAZARDOUS WASTE MANAGEMENT HISTORICAL OVERVIEW The development of the Resource Conservation and Recovery Act of 1976 dates to the passage of the Solid Waste Disposal Act of 1965, which first addressed the issues of waste dis- posal on a nationwide basis. Prior to the 1960s land disposal practices frequently included open burning of wastes to reduce volume, and were controlled only by the general need to avoid creating a public health impact and nuisance, such as a bad smell or visual blight—problems that one could see, smell, taste or touch. At that time, what few landfill con- trols existed were generally focused only on the basics of sanitation, such as rodent control, and the prevention of fires. The early concept of the “sanitary” landfill was to cover the waste with soil to reduce pests and vermin, create separate chambers of earth to reduce the spread of fire, and control odor and unsightly appearance—the key environmental con- cerns of the time. Throughout the ’60s and into the ’70s, the use of indus- trial pits, ponds or lagoons on the land were viewed as legit- imate treatment systems intended to separate solids from liquids and to dissipate much of the liquids. They were not only intended to store waste, but also to treat it. That is, solids would sink when settling occurred and the liquid could be drained, evaporated, or allowed to percolate into the ground. The accumulated solids ultimately would be landfilled. Similarly for protection of receiving waters, pollu- tion control laws prior to the mid-1960s were generally concerned with water-borne diseases and nuisances. The concept of water pollution was far more closely linked to the bacterial transmission of disease and physical obstruc- tion or offense than it was to the impact of trace levels of chemicals. Waterways were viewed as natural systems that could handle waste if properly diluted and if the concentra- tions were within the assimilative capacity of the rivers and streams. The environmental concerns were primarily odor, appearance, oxygen content, and bacterial levels. Individual chemical constituents and compounds, at this time, were not typically regulated in a waterway. The science of testing for and measuring individual con- taminants was unrefined and typically not chemical specific until the 1970s. Water and wastewater analyses were gen- erally limited to indicator parameters, such as Biochemical Oxygen Demand, turbidity, suspended solids, coliform bac- teria, dissolved oxygen, nutrients, color, odor and specific heavy metals. Trace levels of individual chemical com- pounds and hazardous substances as we know them today were not among the parameters regularly analyzed. “Hazardous waste” became a household word in the late 1970s with the publicity surrounding the Love Canal inci- dent. How much waste has been disposed of is still ques- tionable. Unfortunately, significant amounts were “thrown away” over the past decades and have endured in the envi- ronment in drum disposal sites such as “The Valley of the Drums” and in land disposal facilities where they have not degraded. Throughout the ’70s and ’80s significant changes were made in the laws governing environmental protection. New laws adopted in the ’70s include the Clean Air Act, the Federal Water Pollution Control Act, Safe Drinking Water Act, Resource Conservation and Recovery Act (RCRA), Toxic Substance Control Act, Marine Protection Research and Sanctuaries Act, and in 1980 the “Superfund” (CERCLA) statute. Of all the laws passed in the ’70s, RCRA has had the greatest impact on the definition of wastes and the manner in which these wastes were to be managed, treated and handled. RCRA 1 required the US Environmental Protection Agency to establish management procedures for the proper disposal of hazardous wastes. These procedures are part of the Code of Federal Regulations dealing with environmental protection. They cover a “cradle-to-grave” procedure which regulates generators, transporters, storers and disposers of hazardous materials. Regulations for generators and trans- porters of hazardous wastes may also be found in the Code of Federal Regulations. 2,3 Subsequent revisions to RCRA in 1984 included the pro- visions dealing with underground tanks, the restriction of land disposal of a variety of wastes, corrective action require- ments for all releases, and the inclusion of a requirement of © 2006 by Taylor & Francis Group, LLC HAZARDOUS WASTE MANAGEMENT 451 the EPA to inspect government and privately owned facilities which handle hazardous waste. Today the law is again being considered for revision, and among the issues that are always under discussion include “how clean is clean” when remediating industrial and landfill sites. The cleanup standards are not consistent among state and federal programs, frequently causing significant discussion among responsible parties and regulators. At this time, risk assessments are used more often in an effort to design remedial programs that are appropriate for the media, and the resources being protected. A risk assessment might provide, for example, the necessary information to set differing groundwater cleanup goals in a sole source aquifer, than in an industrialized area sit- uated above a brackish water-bearing zone where the ground- water will not again be used for potable purposes. With the preceding paragraphs as general background, the brief discussion which follows on hazardous wastes emphasizes some of the technologies that have been suc- cessfully used for the treatment and disposal of hazardous wastes, and remediation of contaminated properties. HAZARDOUS WASTE DEFINED Hazardous wastes encompass a wide variety of materials. In 1987, the US EPA estimated that approximately 238 million tons could be classified as hazardous. This number is probably generous but suffice it to say that a great deal of material of a hazardous and dangerous nature is generated and disposed of every year. The Resource Conservation and Recovery Act defines a hazardous waste as a solid waste that may cause or signifi- cantly contribute to serious health or death, or that poses a substantial threat to human health or the environment when improperly managed. Solid waste, under the present guide- lines, includes sludges, liquids, and gases in bottles that are disposed of on the land. From this working definition, a number of wastes have been defined as hazardous. These include materials that are ignitable, corrosive, reactive or explosive or toxic. These char- acteristic identifiers are further delineated in the regulations. 4 In addition, using these general characteristics and specific tests, the US Environmental Protection Agency has listed materials from processes, such as electroplating, or specific classes of materials, such as chlorinated solvents, or speci- fic materials, such as lead acetate, or classes of compound, such as selenium and its compounds, which must be managed as “hazardous wastes” when they are disposed. This list changes periodically. In many cases disposers have treated materials not on the list as hazardous if they believe them to be so. Some general classes of materials such as sewage, mining and processing of ore wastes are excluded by law at the present time. Managing Wastes Advancements in science and technology have given us opportunities to address environmental contamination issues in ways that are technologically more advanced, and more cost and time efficient than ever before. Technologies that were unknown, unproven and unacceptable to regulatory agencies just a few years ago, now exist and are being imple- mented at full scale. Regulations have changed, as have gov- ernment policies governing cleanup and enforcement. On a technical level, many ideas for hazardous waste treatment and remediation were rejected a few years ago by the engineering, business and regulatory community as being unproven or unreliable. Entrepreneurial scientists and engineers have adapted their knowledge of manufacturing process chemistry and engineering to the sciences of geol- ogy and hydrogeology and have refined the necessary equip- ment and techniques for waste treatment and remediation. Technologies have been tested at bench and pilot scale, and many have proven effective on a large scale. Pressure by the industrial community for engineers and regulators to reach a common ground has driven the process. Contaminated soil and groundwater remedial techniques have tended toward the “active” end of the spectrum, with the installation of pumps, wells and above ground treatment systems of the capital and labor intensive variety. Progress has been made at the opposite end of the spectrum, rang- ing from intrinsic bioremediation, which involves no active treatment, to incremental levels of treatment that are far less costly than ex-situ pump and treat methods. Programs like the EPA SITE (Superfund Innovative Technology Evaluation) Program and other Federal test and evaluation facilities, University research organizations and privately sponsored technology incubator and test evaluation facilities have been very successful in testing and establishing new hazardous waste treatment and disposal technologies. Currently, there are several dozen organizations nationally that specifically focus on the development of emerging haz- ardous waste treatment technologies. The results have been very positive, and many of today’s front-edge technologies are the offspring of programs such as these. On a regulatory/compliance level, the extensive time frame for receipt of approvals led many companies down the path of the traditional treatment and disposal methods, since they were “proven,” as well as being approvable by the regulatory agencies. Environmental agencies have become more sophisticated, and cleanup levels are more often based on risk rather than standards set at an earlier data in tech- nical and regulatory development. More than ever, agency personnel are now trained as specialists in the various seg- ments of the environmental industry, including risk assess- ment, hydrogeology, remediation engineering and personal protection. As a result, the agencies are often more willing to engage in discussions regarding site specific conditions and remedial goals. Further, modifications to state permit- ting programs have allowed variations on typical operating permits for new and emerging technologies that appear to have promise. An analysis of Superfund remediation activities indi- cates that significant progress has been made in the use of innovative technologies for site remediation. The predomi- nant new technologies used at Superfund sites include soil © 2006 by Taylor & Francis Group, LLC 452 HAZARDOUS WASTE MANAGEMENT vapor extraction (SVE) and thermal desorption. It is impor- tant to note that there are many derivative technologies that will now stand a greater chance of receiving government and industry support as a result. Remediation technologies that are derived from soil vapor extraction include dual phase extraction and sparing. The two phases are typically a) removal of free product or contaminated groundwater and b) vapor. The in-situ addition of certain compounds by sparging into the soil and ground- water has made bioremediation attractive. The addition of the additional components to an earlier technology that was moderately successful has made the modified treatment train much more effective. The new treatment train is therefore more approvable. On a financial level, methods have been developed for the evaluation of large projects to provide a greater degree of financial assurance. The concept of the “unknown” cost of remediation due to the inability of scientists to accurately see and measure subsurface contamination is diminishing. Probabilistic cost analyses are frequently completed on assignments so that final remediation costs can be predicted within a much narrower range. Management practices have changed dramatically over the past 20 years at most industries. They have been driven by the improvements in technologies, as well as the laws and regulations. The real estate boom of the 1980s also impacted operating practices, as many properties were bought and sold during this time. The desire of buyers to be assured that they were purchasing “clean” properties, as well as some state environmental property transfer requirements, was the gen- esis of facility environmental audits as we now know them. For purposes of discussion, hazardous wastes fall primar- ily into two categories, organic and inorganic. Some manage- ment technologies will apply to both, but in general organic material can be destroyed to relatively innocuous end prod- ucts while inorganic material can only be immobilized. The key technologies for hazardous waste management include: • Pollution Prevention • Recycling and Reuse • Waste Minimization • Chemical Treatment and Detoxification • Destruction • Stabilization • Land disposal Of these, land disposal is the least attractive alternative from the standpoint of long-term liability exposure and environ- mental impact. Waste Concentration—A Key Where a waste must be ulti- mately disposed of, concentration or volume reduction is beneficial. The simplest approach to this is to separate wastes at the source; that is, at the place of origin. This will increase handling costs and effort, but will more than pay dividends in minimizing analytical and disposal costs. First, it will mean that analysis must be done less frequently. Second, waste can be disposed of at the lowest degree of care consistent with the most hazardous contaminant, thus minimizing the volume of waste that must get a greater degree of care because of slight cross-contamination by a more toxic material. This is true whether the material is in the liquid or solid state. Another method of reducing volume is concentration. For liquids, this generally means distillation or evapora- tion. Evaporation to date has been acceptable, however, with increased emphasis on the presence of volatile hazardous materials in the atmosphere, evaporation ponds, will, in all probability, no longer meet the necessary standards for waste control and management. In addition, ponds must be per- mitted under RCRA, which imposes additional financial and operating requirements on the waste concentrator. Double and triple effect evaporators and distillation units will be acceptable but are very energy-expensive. Innovative tech- niques will be required because of the high energy of the traditional liquid separation systems. Where a material is dissolved in water or an organic sol- vent, precipitation may be advisable. The solid can then be separated out from the majority of the liquid by filtration or other liquid/solid separation technology. Typical of this would be the precipitation of lead by the use of a sulfide salt, resulting in lead sulfide which has extremely low solubility. The solid may be suitable for reclamation at present or be stored in a secure landfill in a “non- or less-hazardous form” for eventual reuse. Pollution Prevention The passage of Pollution Prevention Laws has driven many industries toward better utilization of their resources. Many companies now actively participate in the preparation and update of a pollution prevention pro- gram, designed to guide personnel toward goals established to improve waste generation and disposal practices. Traditional environmental quality and pollution control programs typically focus on an end-of-pipe approach. The pollution prevention plan approach typically begins earlier in the “equation” by reviewing an operation and making modifications that will positively impact a facility. Some examples include reducing harmful chemical purchases, increasing operation efficiencies, and ultimately generating a smaller quantity of waste. The pollution plan approach will include involvement by a wider range of facility personnel than the traditional environmental management approach. Purchasing, account- ing, production and engineering all participate. Proponents suggest that a program is easy to implement, although corpo- rate personnel involved in the effort know that it is an effort which requires broad-based management support, is time consuming, and not necessarily inexpensive to implement. The benefits are potentially significant, as reduced emissions make it easier to comply with discharge standards, and will reduce long-term liabilities. Recycling and Reuse In many cases, in addition to eco- nomically attractive alternatives, a very attractive alternative will be recycling or reuse of hazardous wastes. The eco- nomic realities of the regulations, where disposal of a barrel of waste can demand a 5–$10 per gallon, and up to $1,200 per © 2006 by Taylor & Francis Group, LLC HAZARDOUS WASTE MANAGEMENT 453 ton or greater fee, may make processing for recycling and/or reuse the best practice. In the present context, we are defining recycling as internal to the plant, and reuse as external to the plant. This is not a legal definition which defines recycling as essentially both internal and external, but it is helpful in this discussion. Internal recycling will require, in general, high efficiency separation and potential additional processing. Thus, if a sol- vent is being recycled, impurities such as water, by-products, and other contaminants must be removed. Depending on the volumes involved, this may be done internally to the process or externally on a batch basis. Reuse involves “selling” the waste to a recycle and reclaimer. The reclaimer then treats the waste streams and recovers value from them. The cleaned-up streams are then his products for sale. From a regulatory, liability perspective, there are advan- tages to reuse as the liability for the waste ends when it is successfully delivered to the reclaimer. Because he pro- cesses the material, he then assumes responsibility for the products and wastes that are generated. If the material is internally recycled, then the recycler, that is the plant, main- tains responsibility for any wastes that are generated as a result of the recycling operation. In some cases, it may be desirable to dispose of wastes directly to the user. This is particularly true when there are large quantities involved and a beneficial arrangement can be worked out directly. Waste exchanges have been organized to promote this type of industrial activity. Detailed discus- sions of their mode of operation can be obtained directly from the exchanges. Waste Minimization The alternative scenario develop- ment will be not only site, but substance specific. Two basic approaches to hazardous waste management are: 1) In-process modifications 2) End-of-pipe modifications Each will have advantages and disadvantages that are pro- cesses, substance, and site specific. In-process alternatives include changing process con- ditions, changing feedstocks, modifying the process form in some cases, or if necessary eliminating that process and product line. In-process modification is generally expensive and must be considered on a case-by-case basis. There are some poten- tial process modifications that should be considered to mini- mize the production of toxic materials as by-products. These include minimization of recycling so side-reaction products do not build up and become significant contributors to the pollution load of a bleed stream. For example, waste must be purged regularly in the chlorination of phenols to avoid the build-up of dioxin. It may also be desirable to optimize the pressure of by-products. For example, phenol is produced and found in condensate water when steam-cracking naphtha to produce ethylene unless pressures and temperatures are kept relatively low. It may be desirable to change feedstocks in order to elim- inate the production of hazardous by-products. For example, cracking ethane instead of naphtha will yield a relatively pure product stream. Hydrazine, a high energy fuel, was originally produced in a process where dimethylnitrosamine was an intermediate. A very small portion of that nitrosamine ended up in a waste stream from an aqueous/hydrocarbon separation. This waste stream proved to be difficult, if not impossible, to dispose of. A new direct process not involving the intermediate has been substituted with the results that there are no noxious wastes or by-products. In the ultimate situation, production of a product may be abandoned because either the product or a resulting by-product poses an economic hazard which the corpo- ration is not willing to underwrite. These include cases where extensive testing to meet TSCA (Toxic Substances Control Act) was required. They include the withdrawal of pre-manufacturing notice applications for some phthalate ester processes. However, production of certain herbicides and pesticides was discontinued because a by-product or contaminant was dioxin. Treatment/Destruction Technology Chemical Treatment/Detoxification Where hazardous mate- rials can be detoxified by chemical reaction, there the mol- ecule will be altered from one that is hazardous to one or more that are non-hazardous, or at least significantly less hazardous. For example, chlorinated hydrocarbons can be hydro-dechlorinated. The resulting products are either HCl or chlorine gas and nonchlorinated hydrocarbons. A number of these processes are being developed for the detoxification of PCB (polychlorinated biphenols) and are being demon- strated as low concentrations of PCB’s in mineral oil. The end products, if concentrated enough, can be useful as feed- stocks or the hydrocarbons may be used as fuel. Cyanide can be detoxified using any number of chemi- cal reactions. These include a reaction with chlorine gas to produce carbonate and chlorine salt. Cyanide can also be converted to cyanate using chlorine gas. In addition, ozone can be utilized to break up the carbon-nitrogen bond and produce CO 2 and nitrogen. Hexavalent chromium is a toxic material. It can be reduced to trivalent chromium which is considerably less hazardous and can be precipitated in a stable form for reuse or disposal as a non-hazardous material. Chromium reduc- tion can be carried out in the presence of sulfur dioxide to produce chromium sulfate and water. Similar chemistry is utilized to remove mercury from caustic chlorine electroly- sis cell effluent, utilizing sodium borohydride. Lead, in its soluble form, is also a particularly difficult material. Lead can be stabilized to a high insoluble form using sulfur compounds or sulfate compounds, thus remov- ing the hazardous material from the waste stream. Acids and bases can most readily be converted to non- hazardous materials by neutralizing them with appropriate © 2006 by Taylor & Francis Group, LLC 454 HAZARDOUS WASTE MANAGEMENT base or acid. This is probably the simplest chemical treat- ment of those discussed and is widely applicable; care must be taken, however, to insure that no hazardous precipitates or dissolved solids forms. Incineration Incineration has been practiced on solid waste for many years. It has not, however, been as widely accepted in the United States as in Europe where incin- eration with heat recovery has been practiced for at least three decades. Incineration of industrial materials has been practiced only to a limited extent; first, because it was more expensive than land disposal, and second, because of a lack of regulatory guidelines. This has changed because land- fills are not acceptable or available, costs for landfilling are becoming extremely high, and regulatory guidance is avail- able. Equipment for incineration of industrial products has been, and is available, however, it must be properly designed and applied. Incineration is the oxidation of molecules at high tem- peratures in the presence of oxygen (usually in the form of air) to form carbon dioxide and water, as well as other oxygenated products. In addition, products such as hydro- gen chloride are formed during the oxidation process. The oxidation, or breakdown, takes place in the gaseous state, thus requiring vaporization of the material prior to any reac- tion. The molecules then breakdown into simpler molecules, with the least stable bonds breaking first. This occurs at rela- tively lower temperatures and shorter times. It is followed by the breakdown of the more stable, and then the most stable bonds to form simple molecules of carbon dioxide, water, hydrogen chloride, nitrogen oxides, and sulfur oxides, as may be appropriate. Thus, the primary considerations for successful oxi- dation or destruction are adequate time and temperature. Good air/waste contact is also important. Regulatory guide- lines require a destruction and removal efficiency (DRE) of 99.99% thus, time and temperature become all the more important. For the most refractory compounds, such as PCB’s, residence times in excess of three seconds and tem- peratures in excess of 1000°C are required. These tempera- tures may be reduced in light of special patented processes utilizing oxidation promoters and/or catalysts. As a result of the high required DRE, a test burn is required to demonstrate adequate design. In addition to time and temperature considerations, there are other important factors which must be consid- ered when designing or choosing equipment to incinerate industrial waste. Most important is adequate emission gas controls. Where materials which contain metals, chlorides, or sulfides are to be incinerated, special provisions must be made to minimize emission of HCl, SO 2 , and metal oxides. Usually a scrubber is required, followed by a system to clean up the scrubber-purge water. This system includes neutralization and precipitation of the sulfur and metal oxides. In addition, where high temperature incineration is practiced, control of nitrogen oxides to meet air quality emissions standards must be considered. These substances do not present insurmountable technological challenges, as they have been handled satisfactorily in coal-fired power plant installations, but they do present added economic and operating challenges. Several types of incineration facilities should be con- sidered. Unfortunately, the standard commercial incinera- tor utilized or municipal waste will generally not prove adequate for handling industrial waste loads because the temperatures and residence times are inadequate. Municipal incinerators are designed to handle wastes with an energy content below 8000 Btu/pound, while industrial wastes can have heating values as high as 24000 Btu/pound. Municipal incinerators are generally not designed to accept industrial wastes. A number of incinerator facilities have been built for industrial wastes. Small, compact units, utilizing a single chamber with after-burner, or two-stage, multi-chamber combustion are available. In general, a single-state unit will not suffice unless adequate residence time can be assured. Rotary kiln incinerators are of particular interest for the disposal of industrial materials. Generally, they are only applicable for large-scale operations, and can handle a large variety of feedstocks, including drums, solids and liquids. Rotary cement kilns have been permitted to accept certain types of organic hazardous materials as a fuel supplement. Of increasing interest for industrial incineration is the fluid bed incinerator. This has the additional advantage of being able to handle inorganic residues, such as sodium sulfate and sodium chloride. These units provide the addi- tional advantage of long residence time, which may be desir- able when the waste is complex (e.g., plastics) or has large organic molecules. On the other hand, gas residence times are short, and an after-burner or off-gas incinerator is often required in order to achieve the necessary DRE. Incineration has been used successfully for the disposal of heptachlor, DDT, and almost all other commercial chlori- nated pesticides. Organo-phosphorous insecticides have also been destroyed, but require a scrubbing system, followed by a mist eliminator, to recover the phosphorous pentoxide that is generated. Some special incineration applications have been imple- mented. These include: • An ammonia plant effluent containing organics and steam is oxidized over a catalyst to form CO 2 , water and nitrogen; • Hydrazine is destroyed in mobile US Air Force trailers which can handle 6 gpm of 100% hydra- zine to 100% water solutions, and maintain an emission has which contains less than 0.03 pound/ minute of NO x ; • Chlorate-phosphorous mixtures from fireworks ammunition are destroyed in a special incinerator which has post-combustion scrubbing to collect NO x , P 4 O 10 , HCl, SO 2 and metal oxides; • Fluid bed incinerators which handle up to 316 tons per day of refinery sludge and 56 tons of caustic are being utilized. © 2006 by Taylor & Francis Group, LLC HAZARDOUS WASTE MANAGEMENT 455 Wet Air Oxidation Although not strictly incineration, wet air oxidation is a related oxidation process. Usually air, and sometimes oxygen, is introduced into a reactor where haz- ardous material, or industrial waste, is slurried in water at 250° to 750°F. Operating pressures are as high as 300 psig. Plants have been built to treat wastes from the manufacture of polysulfite rubber and other potentially hazardous materials. Emissions are similar to those obtained in incineration, with the excep- tion that there is liquid and gaseous separation. Careful eval- uation of operating conditions and materials of destruction are required. Pyrolysis Pyrolysis transforms hazardous organic materi- als by thermal degradation or cracking, in the absence of an oxidant, into gaseous components, liquid, and a solid resi- due. It typically occurs under pressure and a temperature above 800°F. To date, the process has found limited commercial applica- tion but continues to be one that will eventually be economically attractive, the prime reason being the potential for recovery of valuable starting materials. A great deal of experimentation has been carried out both on municipal and industrial wastes. For example, polyvinyl chloride can be thermally degraded to pro- duce HCl and a variety of hydrocarbon monomers, including ethylene, butylene, and propylene. This is a two-stage degrada- tion process with the HCl coming off at relatively low tempera- tures (400°C) and the hydrocarbon polymer chain breakdown can be obtained with Polystyrene, with styrene as the main product, and most other polymers. Experimental work carried out in the early 1970s by the US Bureau of Mines, indicates that steel-belted radial tires can be pyrolyzed to reclaim the monomers, as well as gas and fuel oil. Other target contaminant groups include SVOCs and pesticides. The process is applicable for the treatment of refinery, coal tar, and wood treating wastes and some soils containing hydrocarbons. Disposal Technology Land Storage and Disposal Disposal of hazardous mate- rials to the land remains the most common practice. It is highly regulated and a practice which has been limited because of public pressure and federal rules which require the demonstration of alternate means of disposal. The design of secure landfills for the acceptance of hazardous materials must be such that ground waters, as well as local populations are protected. The US Environmental Protection Agency has implemented strict landfills. In practice all landfills accept- ing hazardous wastes must insure that the wastes stored in close proximity are compatible so that no violent reactions occur should one or more waste leak. Federal and State regulations prohibit the disposal of liquids in landfills. Of equal importance to the disposal of hazardous wastes, whether solid or semi-solid, is the assur- ance that material will not leach away from the landfill or impoundment. This assurance is provided by the use of “double-liners” with a leak detection system between the liners, a leachate collection system for each cell, and a leach- ate treatment system designed and operated for the facility. In dilute form liquid wastes can be “landfarmed” where microbial action will decompose the compounds over time. This methodology has been utilized over many years for hydrocarbons and has worked well. For highly toxic com- pounds, such as chlorinated organics, it is less attractive even though decomposition does occur. Land treatment of PCB contaminated soils has been tested with some success. Stabilization The stabilization of hazardous materials prior to land disposal is frequently practiced. Generally, the stabi- lization is in the form of fixing the hazardous material with a pozzolanic material, such as fly ash and lime, to produce a solid, non-leachable product which is then placed in land dis- posal facilities. Typically, this methodology is applicable to inorganic materials. Most of the commercial processes claim that they can handle materials with some organic matter. Polymer and micro-encapsulation has also been uti- lized but to a significantly lesser extent than the commer- cially available process which utilize pozzolanic reactions. Polymers which have been utilized include polyethylene, polyvinylchloride and polyesters. Grube 9 describes a study of effectiveness of a waste solidification/stabilization process used in a field-scale demonstration which includes collecting samples of treated waste materials and performing laboratory tests. Data from all extraction and leaching tests showed negligible release of contaminants. Physical stability of the solidified material was excellent. Remediation Technologies Natural Attenuation and Bioaugmentation The concept of natural attenuation, or intrinsic bioremediation, has gained a greater acceptance by the regulatory community as data presented by the scientific community have demonstrated the results of natural attenuation, and the costs and time frames associated with traditional remedial methods. 1 This approach is most appropriate for the dissolved phase ground- water contamination plume. It is still necessary to remove or remediate the source zone of an affected aquifer, after which natural attenuation may be a reasonable approach to the dis- solved phases. Natural attenuation should not be considered “No Action.” It requires a solid understanding of the contami- nant, geologic and aquifer characteristics, and a defined plan of action. The action involves demonstrating that the con- taminants will breakdown, will not migrate beyond a speci- fied perimeter, and will not impact potential receptors. It may involve the stimulation of microorganisms with nutrients or other chemicals that will enable or enhance their ability to 1 Example of traditional remediation methods are ex-situ treatment of soil and groundwater, such as soil excavation/disposal, groundwater pump- and-treat using air stripping and granulated carbon polishing. © 2006 by Taylor & Francis Group, LLC 456 HAZARDOUS WASTE MANAGEMENT degrade contaminants. Some limitations may include inappro- priate site hydrogeologic characteristics (including the inability of the geostrata to transport adapted microorganisms) and con- taminant toxicity. Monitoring and reporting is required, and a health-based risk assessment may be required by regulators. Natural attenuation is frequently enhanced by several components, such as the creation of a barrier or the addition of a chemical or biologic additive to assist in the degradation of contaminants. The overall economics of this approach can be sig- nificantly more favorable than the typical pump-and-treat approach. One must be careful to consider, however, that the costs of assessment will equal or exceed that necessary for other methods, and the costs associated with sentinel moni- toring will be borne for a longer period of time. Barriers This has been used in instances where the over- all costs of the remedial action is very high, and the geo- logic features are favorable. It involves the installation of a physical cut-off wall below grade to divert groundwater. The barriers can be placed either upgradient of the plume to limit the movement of clean groundwater through the contaminated media, or downgradient of the plume with openings or “gates” to channel the contaminated groundwa- ter toward a remedial system. This technology has proven to be more efficient and less costly than traditional pump and treat methods, but also requires favorable hydrogeologic conditions. It allows for the return of treated groundwater to the upgradient end of the plume with a continuous “circu- lar” flushing of the soil, rather than allowing the dilution by groundwater moving from the upgradient end of the plume. The result is greater efficiency, and a shorter treatment time period. While the cost of the cutoff wall is significant, it is important to conduct a proper analysis of long-term pump- and-treat costs, including the operation and maintenance of a system that would otherwise be designed to accept a much larger quantity of groundwater. The creation of a hydraulic barrier to divert upgradient groundwater from entering the contaminant plume allows the pumping of groundwater directly from the affected area and often allows the reinjection of the treated water back into the soils immediately upgradient of the plume. This allows for the efficient treatment of the impacted area, with- out unnecessary dilution of the contaminated groundwater plume. It does, however, require an accurate assessment of the groundwater regime during the assessment stage. This promising concept is not radical, but its use in connection with natural remediation is growing rapidly. Passive Treatment Walls Passive treatment walls can be constructed across the flow path of a contaminant plume to allow the groundwater to move through a placed media, such as limestone, iron filings, hydrogen peroxide or microbes. The limestone acts to increase the pH, which can immobi- lize dissolved metals in the saturated zone. Iron filings can dechlorinate chlorinated compounds. The contaminants will be either degraded or retained in concentrated form by the barrier material. Physical Chemical Soil Washing Soil is composed of a multitude of substances, with a large variance in size. These substances range from the very fine silts and clays, to the larger sand, gravel and rocks. Contaminants tend to adsorb onto the smallest soil particles, as a result of the larger sur- face per unit of volume. Although these smaller particles may represent a small portion of the soil volume, they may contain as much as 90% of the contamination. Soil washing involves the physical separation, or clas- sification, of the soil in order to reduce the volume requiring treatment or off-side disposal. It is based on the particle size separation technology used in the mining industry for many decades. The steps vary, but typically begin with crushing and screening. It is a water-based process, which involves the scrubbing of soil in order to cause it to break up into the smallest particles, and its subsequent screening into various piles. The fraction of the soil with the highest concentra- tion of contamination can be treated using technologies fre- quently used by industry. The goal is to reduce the quantity of material that must be disposed. The clean soil fractions can often be returned to the site for use as fill material where appropriate. The use of soil washing technology has some limitations, including a high initial cost for pilot testing and equipment setup. It will be most useful on large projects (requiring reme- diation of greater than 10,000 cubic yards of soil). Sites with a high degree of soil variability, and a significant percentage of larger particles will show the greatest economic benefit. Soil Vapor Extraction Soil Vapor Extraction (SVE) is an effective method for the in-situ remediation of soils contain- ing volatile compounds. Under the appropriate conditions volatile organic compounds will change from the liquid phase to the vapor phase, and can be drawn from the subsur- face using a vacuum pump. There are several factors neces- sary for the successful use of this technology, including 1) the appropriate properties of the chemicals of concern (they must be adequately volatile to move into a vapor phase), and 2) an appropriate vapor flow rate must be established through the soils. Air is drawn into the soils via perimeter wells, and through the soils to the vapor extraction well. It is drawn to the surface by a vacuum pump and subsequently through a series of manifolds to a treatment system such as activated carbon or catalytic oxidation. A concentration gradient is formed, whereby in an effort to reach equilibrium, the liquid phase volatile contaminants change into the vapor phase and are subsequently transported through the soils to the treatment system. This technology is particularly effective for defined spill areas, with acceptable soils. It is most effective in remediating the soils in the vadose zone, the area that is in contact with the fluctuating groundwater table. Groundwater contaminated with these compounds and similar soil conditions can be reme- diated using air sparging, a variation of soil vapor extraction. A variation of this technology is thermal enhanced SVE, using steam/hot air injection or radio frequency heating to increase the mobility of certain compounds. © 2006 by Taylor & Francis Group, LLC HAZARDOUS WASTE MANAGEMENT 457 Air Sparging Air sparging is the further development of soil vapor extraction, wherein that process is extended so that soils and groundwater in the capillary fringe can be effec- tively treated. Air sparging involves injecting air or oxygen into the aquifer to strip or flush volatile contaminants from the groundwater and saturated soils. As the air channels up through the groundwater, it is captured through separate vapor extraction wells and a vapor extraction system. The entire system essentially acts as an in-situ air stripper. Stripped, volatile contaminants usually will be extracted through soil vapor extraction wells and usually require further treatment, such as vapor phase activated carbon or a catalytic oxida- tion treatment unit. This technology is effective when large quantities of groundwater must be treated, and can provide an efficient and cost-effective means of saturated zone soil and groundwater remediation. The biological degradation of organic contamination in groundwater and soil is frequently limited by a lack of oxygen. The speed at which these contaminants are degraded can be increased significantly by the addition of oxygen in either solid or liquid form. Air sparging is often combined with in-situ groundwater bioremediation, in which nutrients or an oxygen source (such as air or peroxide) are pumped into the aquifer through wells to enhance biodegradation of contaminants in the groundwater. Oxygen Enhancement/Oxidation In this in-situ process, hydrogen peroxide is used as a way of adding oxygen to low or anoxic groundwater, or other oxidative chemicals are added as an oxidant to react with organic material present, yielding primarily carbon dioxide and water. The application of this technology is typically through the subsurface injec- tion of a peroxide compound. It has been injected as a liquid, above the plume, and allowed to migrate downward through the contaminated plume. Alternately, it has been placed as a solid in wells located at the downgradient edge of the plume; in this fashion it can act as a contamination “barrier,” limiting the potential for contaminated groundwater to move offsite. As the organic contaminated groundwater moves through the high oxygen zone, the contaminant bonds are either broken, or the increased oxygen aid in the natural biodegradation of the compounds. The process is exothermic, causing a temperature increase in the soils during the process. This acts to increase the vapor pressure of the volatile organic compounds in the soil, and subsequently increases volatilization of the con- taminants. This process can be utilized in connection with a soil vapor extraction and/or sparging system to improve remediation time frames. It does not act, however, on the soil groundwater vadose zone. This may not be a critical flaw, however, since the strate- gic placement of the wells may positively impact the contami- nant concentrations adequately to meet cleanup standards. Dual Phase Extraction Dual phase extraction is an effec- tive method of remediating both soils and groundwater in the vadose and saturated zones where groundwater and soil are both contaminated with volatile or nonvolatile compounds. It is frequently used for contaminant plumes with free floating product, combined with known contami- nation of the vadose zone. This technique allows for the extraction of contaminants simultaneously from both the saturated and unsaturated soils in-situ. While there are several variations of this technique, simply put, a vacuum is applied to the well, soil vapor is extracted and ground- water is entrained by the extracted vapors. The extracted vapors are subsequently treated using conventional treat- ment methods while the vapor stream is typically treated using activated carbon or a catalytic oxidizer. The process is frequently combined with other technolo- gies, such as air sparging or groundwater pump-and-treat to minimize treatment time and maximize recovery rate. Chemical Oxidation and Reduction Reduction/oxidation reactions chemically convert hazardous contaminants to nonhazardous or less toxic compounds that are more stable, less mobile and/or inert. The oxidizing agents typically used for treatment of hazardous contaminants are ozone, hydrogen peroxide, hypochlorites, chlorine and chlorine dioxide. These reactions have been used for the disinfec- tion of water, and are being used more frequently for the treatment of contaminated soils. The target contaminant group for chemical reduction/oxi- dation reactions is typically inorganics, however hydrogen peroxide has been used successfully in the in-situ treatment of groundwater contaminated with light hydrocarbons. Other Technologies Many other technologies are being applied with increasing frequency. The following is only a very brief description of several that have promise. • Surfactant enhanced recovery Surfactant flushing of non-aqueous phase liquids (NAPL) increases the solubility and mobility of the contaminants in water, so that the NAPL can be biodegraded more easily in the aquifer or recovered for treatment aboveground via pump-and-treat methods. • Solvent extraction Solvent extraction has been successfully used as a means of separating haz- ardous contaminants from soils, sludges and sediments, and therefore reducing the volume of hazardous materials that must be treated. An organic chemical is typically used as a solvent, and can be combined with other technologies, such as soil washing, which is frequently used to separate, or classify, various soil particles into size categories. The treatment of the concentrated waste fraction is then treated according to its spe- cific characteristics. Frequently, the larger volume of treated material can be returned to the site. • Bioremediation using methane injection The method earlier described for the injection of hydrogen per- oxide into wells has also been successfully utilized using methane. It is claimed that this bioremedia- tion process uses microbes which co-metabolize methane with TCE and other chlorinated solvents, © 2006 by Taylor & Francis Group, LLC 458 HAZARDOUS WASTE MANAGEMENT potentially cutting treatment costs and time frames by 30 to 50%. • Thermal technologies The EPA has conducted tests of thermally-based technologies in an evalu- ation of methods to treat organic contaminants in soil and groundwater. Low temperature ther- mal desorption is a physical separation process designed to volatilize water and organic contami- nants. Typical desorption designs are the rotary dryer and the thermal screw. In each case, mate- rial is transported through the heated chamber via either conveyors or augers. The volatilized com- pounds, and gas entrained particulates are subse- quently transported to another treatment system for removal or destruction. Mobile incineration processes have been developed for use at remedial sites. While permitting is frequently a problem, the economics of transporting large quantities of soil can drive this alternative. One method is a circulating fluidized bed, which uses high-velocity air to circulate and suspend the waste particles in a combustion loop. Another unit uses electrical resistance heating elements or indirect- fired radiant U-tubes to heat the material passing through the chamber. Each requires subsequent treatment of the off gases. Also certain wastes will result in the formation of a bottom ash, requiring treatment and disposal. In summary, the current business and regulatory climate is positive for the consideration of alternate treatment tech- nologies. The re-evaluation of ongoing projects in light of regulatory and policy changes, as well as new technological developments may allow cost and time savings. The arse- nal of techniques and technologies has developed substan- tially over the years, as has our knowledge of the physical and chemical processes associated with the management of wastes. Effluents and contaminated media are now easier to target with more efficient and cost-effective methods. BIBLIOGRAPHY 1. Pojasek, R.B. (ed.), Toxic and Hazardous Waste Disposal, 1, Processes for Stabilization and Solidification, Ann Arbor Science, Ann Arbor, Michigan, 1979. 2. Merry, A.A. (ed.), The Handbook of Hazardous Waste Management, Technomic, Westport, Connecticut, 1980. 3. Overcash, M.R., Decomposition of Toxic and Nontoxic Organic Com- pounds in Soils, Ann Arbor Science, Ann Arbor, Michigan, 1981. 4. Toxic and Hazardous Industrial Chemicals Safety Manual. The Inter- national Technical Information Institute, Tokyo, 1981. 5. Bertherick, L., Handbook of Reactive Chemical Hazards, Butterworths, London, 1979. 6. Hatayma, H.K., et al., A Method of Determining Hazardous Waste Compatibility, USEPA, Cincinnati, 1981. 7. Kaing, Y. and Metry, A.A., Hazardous Waste Processing Technology, Ann Arbor Science, Ann Arbor, Michigan, 1982. 8. Damages and Threats Caused by Hazardous Material Sites, US EPA/430/9–80/004, USEPA, Washington, 1980. 9. Management of Uncontrolled Hazardous Waste Sites —US EPA Con- ference Proceedings, USEPA, 1980. 10. Stoddard, S.K., et al. , Alternatives to the Land Disposal of Hazardous Wastes — An Assessment for California, Office of Appropriate Technol- ogy, State of California, 1981. 11. Grube, W.E., Jr., “Evaluation of Waste Stabilized by the Solid Tech Site Technology,” J. Air Waste Manag. Assoc. (1990). 12. Evanoff, S.P., Hazardous Waste Reduction in the Aerospace Industry, Chem. Eng. Prog. , 86, 4, 51 (1990). 13. Jackson, D.R., Evaluation of Solidified Residue from Municipal Solid Waste Combustor, EPA Repot 600/52–89/018 Feb. 1990. 14. Innovative Hazardous Waste Treatment Technologies: A Developers Guide to Support Services, Third Edition, EPA Report EPA/542-B- 94–012, September 1994. 15. Hazardous Waste Clean-up Information Database ( CLU-IN ), US EPA, 1996. 16. Innovative Treatment Technologies: Annual Status Report ( Seventh Edition) Applications of New Technologies at Hazardous Waste Sites, USEPA Report EPA-542-R-95–008, Number 7, Revised September 1995. 17. Remediation Case Studies: Soil Vapor Extraction, USEPA Report EPA- 542-R-95–004, March 1995. 18. Superfund Innovative Technology Evaluation Program, Technology Profiles Seventh Edition, USEPA Report, EPA/540/R-94/526, Novem- ber 1994. 19. Superfund XV Abstract Book, Hazardous Materials Control Resources Institute, November 1994. 20. Remediation Technologies Screening Matrix and Reference Guide, USEPA Report, EPA 542-B-93–005, July 1993. 21. Remediation Case Studies: Thermal Desorption, Soil Washing, and In Situ Vitrification, USEPA Report, EPA-542-R-95–005, March 1995. 22. Proceedings, Fifth Forum on Innovative Hazardous Waste Treatment Technologies: Domestic and International, USEPA Report, EPA/540/ R-94/503, May 1994. 23. LaGreca, M.D., Buckingham, P.L., Evans, J.C., Hazardous Waste Man- agement, McGraw-Hill, Inc., 1994. 24. Freeman, H.M. (ed.), Standard Handbook of Hazardous Waste Treat- ment and Disposal, McGraw-Hill, Inc., 1989. 25. Sell, N.J., Industrial Pollution Control: Issues and Techniques, Second Edition, Van Nostrand Reinhold, 1992. 26. Corbitt, R.A. (ed.), Standard Handbook of Environmental Engineering, McGraw-Hill, Inc., 1990. 27. Kolluru, R.V. (ed.), Environmental Strategies Handbook, A Guide to Effective Policies & Practices, McGraw-Hill, Inc., 1994. REFERENCES 1. PL 95-580, Resource Conservation and Recovery Act of 1976, 42 USC 6901, 1976. 2. 40 CFR 262. 3. 40 CFR 263. 4. 40 CFR 261. 5. 40 264, 265. 6. SW-968, Permit Applicants’ Guidance Manual for the General Facility Standards of 40 CFR 264, Oct. 1983. 7. Lindgren, G.D., “Managing Industrial Hazardous Waste: A Practical Handbook,” 350 pp., 1989, Lewis Publ., Boca Raton, FL. 8. Industrial Pollution Prevention Planning, Meeting Requirements Under the New Jersey Pollution Prevention Act, New Jersey Department of Environmental protection, Office of Pollution Prevention, September 1985, Second Edition. 9. Grube, W.E., Jr., “Evaluation of Waste Stabilized by the Solid Tech Site Technology,” J. Air Waste Manag. Assoc. , 40 310 (1990). RICHARD T. DEWLING GREGORY A. PIKUL Dewling Associates, Inc. © 2006 by Taylor & Francis Group, LLC . knowledge of manufacturing process chemistry and engineering to the sciences of geol- ogy and hydrogeology and have refined the necessary equip- ment and techniques for waste treatment and remediation on hazardous wastes emphasizes some of the technologies that have been suc- cessfully used for the treatment and disposal of hazardous wastes, and remediation of contaminated properties. HAZARDOUS. chambers of earth to reduce the spread of fire, and control odor and unsightly appearance—the key environmental con- cerns of the time. Throughout the ’60s and into the ’70s, the use of indus- trial