hazardous waste

Dictionary: hazardous waste

n.
A substance, such as nuclear waste or an industrial byproduct, that is potentially damaging to the environment and harmful to humans and other living organisms.

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Sci-Tech Encyclopedia: Hazardous waste

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Any solid, liquid, or gaseous waste materials that, if improperly managed or disposed of, may pose substantial hazards to human health and the environment. Every industrial country in the world has had problems with managing hazardous wastes. Improper disposal of these waste streams in the past has created a need for very expensive cleanup operations. Efforts are under way internationally to remedy old problems caused by hazardous waste and to prevent the occurrence of other problems in the future.

A waste is considered hazardous if it exhibits one or more of the following characteristics: ignitability, corrosivity, reactivity, and toxicity. Ignitable wastes can create fires under certain conditions; examples include liquids, such as solvents, that readily catch fire, and friction-sensitive substances. Corrosive wastes include those that are acidic and those that are capable of corroding metal (such as tanks, containers, drums, and barrels). Reactive wastes are unstable under normal conditions. They can create explosions, toxic fumes, gases, or vapors when mixed with water. Toxic wastes are harmful or fatal when ingested or absorbed. When they are disposed of on land, contaminated liquid may drain (leach) from the waste and pollute groundwater.

Hazardous wastes may arise as by-products of industrial processes. They may also be generated by households when commercial products are discarded. These include drain openers, oven cleaners, wood and metal cleaners and polishes, pharmaceuticals, oil and fuel additives, grease and rust solvents, herbicides and pesticides, and paint thinners.

The predominant waste streams generated by industries in the United States are corrosive wastes, spent acids, and alkaline materials used in the chemical, metal-finishing, and petroleum-refining industries. Many of these waste streams contain heavy metals, rendering them toxic. Solvent wastes are generated in large volumes both by manufacturing industries and by a wide range of equipment maintenance industries that generate spent cleaning and degreasing solutions. Reactive wastes come primarily from the chemical industries and the metal-finishing industries. The chemical and primary-metals industries are the major sources of hazardous wastes.

There is a growing acceptance throughout the world of the desirability of using waste management hierarchies for solutions to problems of hazardous waste. A typical sequence involves source reduction, recycling, treatment, and disposal. Source reduction comprises the reduction or elimination of hazardous waste at the source, usually within a process. Recycling is the use or reuse of hazardous waste as an effective substitute for a commercial product or as an ingredient or feedstock in an industrial process.

Treatment is any method, technique, or process that changes the physical, chemical, or biological character of any hazardous waste so as to neutralize such waste; to recover energy or material resources from the waste; or to render such waste nonhazardous, less hazardous, safer to manage, amenable for recovery, amenable for storage, or reduced in volume. Disposal is the discharge, deposit, injection, dumping, spilling, leaking, or placing of hazardous waste into or on any land or body of water so that the waste or any constituents may enter the air or be discharged into any waters, including groundwater.

There are various alternative waste treatment technologies, for example, physical treatment, chemical treatment, biological treatment, incineration, and solidification or stabilization treatment. These processes are used to recycle and reuse waste materials, reduce the volume and toxicity of a waste stream, or produce a final residual material that is suitable for disposal. The selection of the most effective technology depends upon the wastes being treated.

There are abandoned disposal sites in many countries where hazardous waste has been disposed of improperly in the past and where cleanup operations are needed to restore the sites to their original state. Cleaning up such sites involves isolating and containing contaminated material, removal and redeposit of contaminated sediments, and in-place and direct treatment of the hazardous wastes involved. As the state of the art for remedial technology improves, there is a clear preference for processes that result in the permanent destruction of contaminants rather than the removal and storage of the contaminating materials.

Real Estate Dictionary: Hazardous Waste

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A type of solid waste that poses a significant threat to human health.
Example: A list of hazardous waste substances is provided in Rcra.

Dental Dictionary: hazardous waste

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Any material, gas, liquid, or solid substance that has the potential to cause injury or illness; that in an unprotected state poses a risk to the environment, including plant or animal life.

Encyclopedia of Public Health: Hazardous Waste

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All human activities generate some form of waste. In its most general sense, the term "hazardous waste" comprises toxic chemicals, radioactive materials, and biologic or infectious waste. Hazardous waste poses a threat to workers through occupational exposure and to the public through exposure in homes, communities, and the general environment. Exposure may occur near the site of generation, along transportation corridors, and near the ultimate disposal sites. Most hazardous waste results from industrial processes that yield unwanted intermediates, products that fail quality control, and spilled material.

Hazardous waste management is divided into two main areas: currently generated waste, which is regulated under the Resource Conservation and Recovery Act (RCRA) of 1976, and waste at abandoned sites, which is regulated under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980. The Environmental Protection Agency (EPA) has jurisdiction and responsibility for managing the "cleanup" of hazardous waste sites. The Agency for Toxic Substances and Disease Registry (ATSDR), a branch of the Centers for Disease Control and Prevention (CDC), evaluates and assists communities that have been exposed to hazardous waste.

Under RCRA, industries assume responsibility for all of the waste they generate. They may manage it on-site or ship it off-site. In the latter case they retain responsibility, even when it has reached a legal disposal site. This is termed "cradle-to-grave" responsibility. Under CERCLA (also known as the Superfund Act), states may petition the EPA to have a hazardous waste site listed on the National Priorities List. This makes the site eligible for federal cleanup assistance in the event that a responsible party is not identified or does not accept responsibility.

Under RCRA, solid waste is defined as hazardous if its "quantity, concentration, or physical, chemical, or infectious characteristic" leads to death or serious illness or otherwise poses a "substantial present or potential hazard to human health or the environment, when improperly treated, stored, transported, or disposed of, or otherwise mismanaged." Under the Toxic Substances Control Act, more than 55,000 individual chemicals can fit the definition of a hazardous waste.

The main types of hazardous wastes are depleted raw materials, reaction products, tank residues, filter cake, precipitates, and spent solvents. They may be disposed of in liquid or solid form, either contained or uncontained. Wastes must be listed on a manifest, hauled by a licensed hauler, and disposed of at an approved hazardous waste site.

It is estimated that hazardous chemical wastes have been stored at more than 50,000 sites in the United States alone, although only 1,500 are listed on the National Priorities, or Superfund, List. To be listed, a site must be assessed using the EPA Hazard Ranking System. Once the site is identified, a preliminary site assessment is performed to determine if there is a potential hazard. If a hazard exists, there may be emergency remediation, but typically the second phase is a remedial investigation/feasibility study that categorizes a site and identifies remediation options. Remediation may range from an enclosure and warning signs to complete removal of waste, capping, and treatment of groundwater.

The Hazard Ranking System yields three scores, involving: (1) the possibility of offsite migration; (2) the likelihood of human receptors coming in contact with contaminated air, water, soil, or organisms; and (3) the explosivity or fire hazard posed by the material.

The ten substances most often identified at Superfund sites are: trichloroethylene, toluene, benzene, lead, chloroform, polychlorinated biphenyls (PCBs), tetrachloroethylene, phenol, trichloroethane, and chromium. The receptor populations include not only neighbors living adjacent to industrial sources or waste sites, but emergency responders, public safety officials, regulatory agency personnel, and hazardous-waste remediation workers.

Pathways of exposure include: direct contact with contaminated soil from playing or working on or adjacent to a waste site, consumption of contaminated groundwater, inhalation of vapors or dust from a site, and consumption of contaminated food stuffs.

Bibliography

Gochfeld, M. (1995). "Hazardous Waste." In Textbook of Occupational and Environmental Medicine, eds. L. Rosenstock and M. Cullen. Philadelphia, PA: W. B. Saunders.

Gochfeld, M., and Burger, J. (1995). "Assessment and Mediation of Hazardous Waste Sites." In Environmental Medicine, ed. S. Brooks et al. St. Louis, MO: Mosby.

— MICHAEL GOCHFELD

US History Encyclopedia: Hazardous Waste

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Hazardous Waste is a by-product, usually of manufacturing, medical and scientific research, and consumer detritus (disintegrating materials), that is dangerous to human health and wildlife. The substances defined as hazardous received their initial analysis in the industrial hygiene movement between 1900 and 1930, which focused on substances in the workplace. The movement's concern with hazardous industrial substances seldom extended beyond the factory walls. Although public health authorities in the late nineteenth century considered industrial pollution a major problem, the focus shifted after the acceptance of the germ theory of disease. Public health officers and sanitary engineers focused on bacterial wastes as the primary threat to human health. When they considered industrial wastes, they concentrated on their non-pathogenic effects. It was only after World War II that professionals began to pay greater attention to health and the environment.

The first federal legislation regarding hazardous waste was the 1970 Solid Waste Disposal Act. Section 212 required that the Environmental Protection Agency (EPA) investigate the storage and disposal of hazardous wastes. The resulting 1974 report to Congress on the disposal of hazardous wastes led to the passage in 1976 of the Resource Conservation and Recovery Act (RCRA), which defined hazardous wastes that can cause illness or pose a hazard to health and to the environment when improperly stored, transported, or managed. In 1980, the EPA announced regulations implementing cradle-to-grave controls for handling hazardous wastes.

RCRA did not touch on the dangers of wastes buried in industrial and municipal landfills. For decades, industries had disposed of hazardous materials in landfills. Land disposal of wastes increased in the post-World War II period, as states put limits on water disposal. These older sites, in many cases abandoned or closed, posed a threat to groundwater supplies. The case of Love Canal, a chemical waste dump formed by the Hooker Chemical and Plastics Corporation in Niagara Falls, New York, and from which toxic chemical wastes migrated to endanger neighboring residential areas, focused public and govern-mental attention on the problem in the late 1970s.

Congress responded to the perceived danger of these sites in 1980 by approving the Comprehensive Environ-mental Response, Compensation, and Liability Act (CERCLA), or Superfund, which provided $1.6 billion for the cleanup of toxic wastes. Under CERCLA, the EPA established procedures of site-specific risk assessments to determine whether the hazardous wastes were a threat to human health. The Superfund Amendments and Reauthorization Act in 1986 increased the fund to $9.6 billion. The Superfund Act and its amendments sought to cover the costs of cleanup by requiring retrospective liability. That is, it made those people and companies responsible for creating hazardous waste sites liable for the costs of cleanup. The amendments also required that firms that imported, processed, or produced more than 50,000 pounds per year of any of the EPA's listed chemicals and compounds, register them in the EPA's annual Toxics Release Inventory. The slow pace of cleanups, however, as well as cumbersome procedures, convinced many experts that Superfund was not only underfunded but imposed unreasonable standards of cleanliness, given future site uses.

One of Superfund's main tools was a trust fund that contained money contributed by corporations that were taxed to help pay for cleanup operations at Superfund sites. In 1995, that legislation expired. In the following years, Democratic President Bill Clinton annually attempted to renew the legislation, but the Republican-controlled legislature consistently blocked his efforts. Once Republican President George W. Bush came into office, the White House ceased to agitate for renewal. Many critics see the Superfund program as fundamentally flawed because it spends too much money in court battles to determine who is responsible for cleaning up hazardous sites. Furthermore, they argue that taxing the chemical and petrochemical industries to clean up sites that they did not pollute is unfair. In 2001, $860 million was available for Superfund cleanup, but that amount was projected to fall to $28 million by 2003.

Bibliography

Anderson, Terry L., ed. Political Environmentalism: Going Behind the Green Curtain. Stanford, CA: Hoover Institution Press, 2000.

Barnett, Harold C. Toxic Debts and the Superfund Dilemma. Chapel Hill: University of North Carolina Press, 1994.

Hird, John A. Superfund: The Political Economy of Environmental Risk. Baltimore: Johns Hopkins University Press, 1994.

Mazur, Allan. A Hazardous Inquiry: The Rashomon Effect at Love Canal. Cambridge, Mass: Harvard University Press, 1998.

Switzer, Jacqueline Vaughn. Environmental Politics: Domestic and Global Dimensions. New York: St. Martin's Press, 1994; 1998.

Wikipedia: Hazardous waste

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This High Priority may require cleanup to meet Wikipedia's quality standards. Please improve this High Priority if you can. (November 2008)

A hazardous waste is waste that poses substantial or potential threats to public health or the environment and generally exhibits one or more of these characteristics:

carcinogenic
ignitable (i.e., flammable)
oxidant
corrosive
toxic
radioactive
explosive

U.S. environmental laws (see Resource Conservation and Recovery Act) additionally describe a "hazardous waste" as a waste (usually a solid waste) that has the potential to:

cause, or significantly contribute to an increase in mortality (death) or an increase in serious irreversible, or incapaitating reversible illness; or

pose a substantial (present or potential) hazard to human health or the environment when improperly treated, stored, transported, or disposed of, or otherwise managed.

These wastes may be found in different physical states such as gasses, liquids, or solids. Furthermore, a hazardous waste is a special type of waste because it cannot be disposed of by common means like other by-products of our everyday lives. Depending on the physical state of the waste, treatment and solidification processes might be available. In other cases, however, there is not much that can be done to prevent harm.

Regulatory history

Resource Conservation and Recovery Act (RCRA)

Modern hazardous waste regulations in the U.S. began with the Resource Conservation and Recovery Act (RCRA) which was enacted in 1976. The primary contribution of RCRA was to create a "cradle to grave" system of record keeping for hazardous wastes. Hazardous wastes must be tracked from the time they are generated until their final disposition.

RCRA's record keeping system helps to track the life cycle of hazardous waste and reduces the amount of hazardous waste illegally disposed.

Comprehensive Environmental Response, Compensation, and Liability Act

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), was enacted in 1980. The primary contribution of CERCLA was to create a "Superfund" and provided for the clean-up and remediation of closed and abandoned hazardous waste sites.Before this act was created, hazardous wastes were being disposed in regular landfills until scientists measured unfavorable amounts of hazardous materials seeping into the ground. These chemicals eventually made their way to the water systems, and contaminated the soil that animals and crops used, as well as the soil that people employed to build their communities. After these regulations were put into practice, many landfills require now countermeasures against groundwater contamination; for example installing a barrier along the foundation of the landfill to contain the hazardous substances that may remain in the disposed waste.^[1]Currently, in order to enter a landfill, hazardous wastes must be stabilized and solidified, thus the new waste produced is less harmful than the original.

Hazardous wastes in the United States

Many types of businesses generate hazardous waste. Some are small areas that may be located in a community. For example, dry cleaners, automobile repair shops, hospitals, exterminators, and photo processing centers all generate hazardous waste. Some hazardous waste generators are larger companies like chemical manufacturers, electroplating companies, and oil refineries.

A US facility that treats, stores or disposes of hazardous waste must obtain a permit for doing so under the Resource Conservation and Recovery Act. Generators of and transporters of hazardous waste must meet specific requirements for handling, managing, and tracking waste. Through the RCRA, Congress directed the United States Environmental Protection Agency (EPA) to create regulations to manage hazardous waste. Under this mandate, the EPA developed strict requirements for all aspects of hazardous waste management including the treatment, storage, and disposal of hazardous waste. In addition to these federal requirements, states may develop more stringent requirements or requirements that are broader in scope than the federal regulations.

In the United States, hazardous wastes generated by commercial or industrial activities may be classified as "listed" hazardous wastes or "characteristic" hazardous wastes by the EPA.

In regulatory terms, a Resource Conservation and Recovery Act (RCRA) hazardous waste is a waste that either a "characteristic waste" or a "listed waste":

Characteristic Waste - exhibits at least one of the four "characteristics" of hazardous waste (ignitability, corrosivity, reactivity, or toxicity)

Listed Waste - appears on one of the four hazardous wastes lists (F-list, K-list, P-list, or U-list), or

Individual states may regulate particular wastes more stringently than mandated by federal regulation. This is because the U.S. EPA is authorized to delegate primary rulemaking authorization to individual states. Most states take advantage of this authority, implementing their own hazardous waste programs that are at least as stringent as the federal program.

Characteristic wastes

Characteristic Hazardous Wastes are defined as wastes that exhibit the following characteristics: ignitability, corrosivity, reactivity, or toxicity.

Ignitability

Ignitable wastes can create fires under certain conditions, are spontaneously combustible, or have a flash point less than 60 °C (140 °F). Examples include waste oils and used solvents. For more details, see 40 CFR §261.21. Test methods that may be used to determine ignitability include the Pensky-Martens Closed-Cup Method for Determining Ignitability, the Setaflash Closed-Cup Method for Determining Ignitability, and the Ignitability of Solids.

Corrosive

Corrosive wastes are acids or bases (pH less than or equal to 2, or greater than or equal to 12.5) that are capable of corroding metal containers, such as storage tanks, drums, and barrels. Battery acid is an example. For more details, see 40 CFR §261.22. The test method that may be used to determine corrosivity is the Corrosivity Towards Steel (Method 1110A) (PDF).

Reactivity

Reactive wastes are unstable under "normal" conditions. They can cause explosions, toxic fumes, gases, or vapors when heated, compressed, or mixed with water. Examples include lithium-sulfur batteries and explosives. For more details, see 40 CFR §261.23. There are currently no test methods available.

]

Listed wastes

Listed hazardous wastes are generated by specific industries and processes and are automatically considered hazardous, based solely on the process that generates them and irrespective of whether a test of the waste shows any of the "characteristics" of hazardous waste. Examples of listed wastes include:

many sludges leftover from electroplating processes.
certain waste from iron and steel manufacturing
wastes from certain cleaning and/or degreasing processes

Hazardous wastes are incorporated into lists published by the Environmental Protection Agency. These lists are organized into three categories:

The F-list (non-specific source wastes)

This list identifies wastes from common manufacturing and industrial processes, such as solvents, that have been used in cleaning or degreasing operations. Because the processes producing these wastes can occur in different sectors of industry, the F-listed wastes are known as wastes from non-specific sources.

The K-list (source-specific wastes)

This list includes certain wastes from specific industries, such as petroleum refining or pesticide manufacturing. Certain sludges and wastewaters from treatment and production processes in these industries are examples of source-specific wastes.

Discarded wastes (P-List and U-List)

P-List and U-List wastes are actually sublists of the same major list applying to discarded wastes. These wastes apply to commercial chemical products that are considered hazardous when discarded and are regulated under the following U.S. Federal Regulation: 40 C.F.R. 261.33(e) and 261.33(f). P-List wastes are wastes that are considered "acutely hazardous" when discarded and are subject to more stringent regulation. Nitric oxide is an example of a P-list waste and carries the number P076. U-Listed wastes are considered "hazardous" when discarded and are regulated in a somewhat less stringent manner than P-Listed wastes.

Universal wastes

Universal wastes are hazardous wastes that (in the U.S.):

generally pose a lower threat relative to other hazardous wastes
are ubiquitous and produced in very large quantities by a large number of generators.

Some of the most common "universal wastes" are: fluorescent light bulbs, some specialty batteries (e.g. lithium or lead containing batteries), cathode ray tubes, and mercury-containing devices.

Universal wastes are subject to somewhat less sringent regulatory requirements and small quantity generators of universal wastes may be classified as "conditionally-exempt small quantity generators" (CESQGs) which releases them from some of the regulatory requirements for the handling and storage hazardous wastes.

Universal wastes must still be disposed of properly. (For more information, see Fact Sheet: Conditionally Exempt Small Quantity Generator)

Other hazardous wastes

The U.S. Environmental Protection Agency has other ways of regulating hazardous waste. These "rules" include:

The "Mixture Rule" - 400 CFR Section 261-23 (incorrect citation)

applies to a mixture of a listed hazardous waste and a solid waste and states that the result of a mixture of these two wastes is regulated as a hazardous waste. Exemptions may apply in some cases.

The "Derived-from Rule" - 40 CFR Section 261.3(b) applies to a waste that is generated from the treatment, storage or disposal of a hazardous waste (for example, the ash from the incineration of hazardous waste). Wastes "derived" in this manner may be regulated as hazardous wastes.

The "Contained-in Rule" - - 40 CFR Section 261.3(f) applies to soil, groundwater, surface water and debris that are contaminated with a listed hazardous waste.

Exempted hazardous wastes

USEPA regulations automatically exempt certain solid wastes from being regulated as "hazardous wastes". This does not necessarily mean the wastes are not hazardous nor that they are not regulated. An exempted hazardous waste simply means that the waste is not regulated by the primary hazardous waste regulations. Many of these wastes may by regulated by different statutes and/or regulations and/or by different regulatory agencies. For example, many hazardous mining wastes are regulated via mining statutes and regulations. "Exempted" hazardous wastes include:

Household hazardous waste (HHW); (see below)
Agricultural wastes which are returned to the ground as fertilizer;
Mining overburden returned to the mine site;
Utility wastes from [coal] combustion to produce electricity;
Oil and natural gas exploration drilling waste;
Wastes from the extraction of beneficiation, and processing of ores and minerals, including coal;
Cement kiln wastes;
Wood treated with arsenic preservatives.
Certain chromium-containing wastes (See Code of Federal Regulations Section 261.4(b))
Recycled hazardous wastes: Some hazardous wastes that are recycled may also be exempted from hazardous waste regulations.

Household Hazardous Waste

Household Hazardous Waste (HHW) (also referred to as domestic hazardous waste) is waste that is generated from residential households. HHW only applies to wastes that are the result of the use of materials that are labeled for and sold for "home use".

The following list includes categories often applied to HHW. It is important to note that many of these categories overlap and that many household wastes can fall into multiple categories:

Paints and solvents
Automotive wastes (used motor oil, antifreeze, etc.)
Pesticides (insecticides, herbicides, fungicides, etc.)
Mercury-containing wastes (thermometers, switches, fluorescent lighting, etc)
Electronics (computers, televisions, cell phones)
Aerosols / Propane cylinders
Caustics / Cleaning agents
Refrigerant-containing appliances
Some specialty Batteries (e.g. lithium, nickel cadmium, or button cell batteries)
Ammunition
Radioactive waste (some home smoke detectors are classified as radioactive waste because they contain very small amounts of a radioactive isotope of americium (see: Disposing of Smoke Detectors).

Disposal of HHW in the United States

Because of the expense associated with the disposal of HHW, it is still legal for most homeowners in the U.S. to dispose of most types of household hazardous wastes as municipal solid waste (MSW) and these wastes can be put in your trash. Laws vary by state and municipality and they are changing every day. Be sure to check with your local environmental regulatory agency, solid waste authority, or health department to find out how HHW is managed in your area.

Modern landfills are designed to handle normal amounts of HHW and minimize the environmental impacts. However, there are still going to be some impacts and there are many ways that homeowners can keep these wastes out of landfills.^[2]

Laws regulating HHW in the U.S. are gradually becoming more strict. As of 2007, radioactive smoke detectors are the only HHW that are managed nationally. While it is still legal in the United States to dispose of smoke detectors in your trash in most places, manufacturers of smoke detectors must accept returned units for disposal as mandated by the Nuclear Regulatory law 10 CFR 32.27. If you send your detector back to a manufacturer then it will be disposed in a nuclear waste facility.

In the U.S., states are regulating various HHW waste disposal in MSW landfills on a state by state basis. Some commonly regulated wastes in some (but not all) states include restrictions on the disposal of:

Recyclables (especially "source-separated" recyclables or recyclables that have already been separated from solid waste). In this case this would only apply to household hazardous wastes that have been separated for recycling.
Lead-acid batteries
Mercury-containing wastes
Rechargeable batteries
Cathode ray tubes (CRTs) from older computer monitors and televisions
Cell phones and computers
Refrigerant containing appliances such as a refrigerator, air conditioner or dehumidifier.

(Note: Yard waste or "green waste" (particularly "source-separated" yard waste such as from a city leaf collection program) is not hazardous but may be a regulated household waste)

Local solid waste authorities and health departments may also have specific bans on wastes that apply to their service area.

Solid Waste Haulers and HHW - One "catch-22" that residents often encounter is that while it may be legal to dispose of some HHW in their regular trash, the waste hauler that collects the trash can choose not to haul the waste. It is not uncommon for a waste hauler to refuse to pick up municipal solid waste that contains things like paint and fluorescent light bulbs. There is often little recourse for residents in this case. In these cases the resident may have to make their own arrangements to dispose of the waste by taking it directly to a landfill or solid waste transfer station.

Final disposal of hazardous waste

Hazardous wastes undergo different treatments in order to stabilize and dispose of them.

Recycling

Many HWs can be recycled into new products. Examples might include lead-acid batteries or electronic circuit boards where the heavy metals can be recovered and used in new products.Another example is the ash generated by coal-fired power plants; these plants produced two types of these residues: fly and bottom ash. Fly ash particles have a low density, are very fine, and are removed by air pollution control devices. On the other side, bottom ash is a dense, dark, gravely substance that remains on the bottom of combustion chambers.^[3] After these types of ashes go though the proper treatment, they could bind to other pollutants and convert them into easier-to- dispose solids, or they could be used as pavement filling. Such treatments reduce the level of threat of harmful chemicals, like fly and bottom ash, while also recycling the safe product and helping the environment.

Portland cement

Another commonly used treatment is cement based solidification and stabilization. Cement is used because it can treat a range of hazardous wastes by improving physical characteristics and decreasing the toxicity and transmission of contaminants. The cement produced is categorized into 5 different divisions, depending on its strength and components. This process of converting sludge into cement might include the addition of pH adjustment agents, phosphates, or sulfur reagents to reduce the settling or curing time, increase the compressive strength, or reduce the leach ability of contaminants.

Neutralization

Some HW can be processed so that the hazardous component of the waste is eliminated. making it a non-hazardous waste. An example of this might include a corrosive acid that is neutralized with a basic substance so that it is no-longer corrosive. (see acid-base reactions.)Another mean to neutralize some of the waste is pH adjustment. pH is an important factor on the leaching activity of the hazardous waste. By adjusting the pH of some toxic materials, we are reducing the leaching ability of the waste.

Incineration, destruction and waste-to-energy

A HW may be "destroyed" for example by incinerating it at a high temperature. Flammable wastes can sometimes be burned as energy sources. For example many cement kilns burn HWs like used oils or solvents. Today incineration treatments not only reduce the amount of hazardous waste. They also generate energy throughout the gases released in the process. It is known that this particular waste treatment releases toxic gases produced by the combustion of byproduct or other materials and this can affect the environment. However, current technology has developed more efficient incinerator units that control these emissions to a point that this treatment is considered a more beneficial option. There are different types of incinerators and they vary depending on the characteristics of the waste. Starved air incineration is another method used to treat hazardous wastes. Just like in common incineration, burning occurs, however controlling the amount of oxygen allowed proves to be significant to reduce the amount of harmful bi products produced. Starved Air Incineration is an improvement of the traditional incinerators in terms of air pollution. Using this technology it is possible to control the combustion rate of the waste and therefore reduce the air pollutants produce in the process.

Hazardous waste landfill (sequestering, isolation, etc.)

A HW may be sequestered in a HW landfill or permanent disposal facility. "In terms of hazardous waste, a landfill is defined as a disposal facility or part of a facility where hazardous waste is placed in or on land and which is not a pile, a land treatment facility, a surface impoundment, an underground injection well, a salt dome formation, a salt bed formation, an underground mine, a cave, or a corrective action management unit (40 CFR 260.10)."^[4]^[5]

Pyrolysis

Some hazardous waste types may be eliminated using pyrolisis in an ultra high temperature electrical arc, in inert conditions to avoid combustion. This treatment method may be preferable to high temperature incineration in some circumstances such as in the destruction of concentrated organic waste types, including PCBs, pesticides and other persistent organic pollutants. ^[6] ^[7]

References

^ Chaudhary R., Rachana M., 2006. Factors affecting hazardous waste solidification/stabilization: A Review. In: Journal of Hazardous Materials B137 pp.267–276
^ USEPA Household Hazardous Wastes
^ Munson-McGee S.H., Parsa, J., Steiner, R., 1996. Stabilization/solidification of hazardous wastes using fly ash. In: Journal of Environmental Engineering, 122 (10), pp. 935-940.
^ Hazardous Waste Landfills
^ Land Disposal Units
^ [1]
^ [2]

External links

Environmental Hazardous Waste Cleanup Company Environmental Cleanup Services
Agency for Toxic Substances and Disease Registry
The EPA's hazardous waste page
The U.S. EPA's Hazardous Waste Cleanup Information System
What Did We Know About Hazardous Waste and When Did We Know It, a February 2002 essay by William Sanjour

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