Hazardous-Waste Disposal

Summary

Hazardous waste disposal involves transporting hazardous materials to appropriate facilities for treatment, recycling, and possible storage in a manner that will protect the environment and public health. Materials that are radioactive, toxic, corrosive, ignitable, irritating, poisonous, and infectious are examples of hazardous wastes that threaten human health. Moreover, some hazardous wastes, such as mercury, present a danger because they accumulate in the environment when they are improperly managed. Although manufacturing companies are most often thought to be the entities that generate hazardous wastes, there is a diversity of generators, from farms to nuclear power plants to households.

Definition and Basic Principles

Hazardous waste disposal is the cradle-to-grave management of materials that threaten human health and the environment. Hazardous wastes are ubiquitous and their proper disposal is a global issue. In fact, industrialized nations are still involved in the cleanup of hazardous wastes that contaminated land and waters before disposal laws were adopted and enforced. One method of recycling hazardous waste sites is to clean up the waste and designate the land as a brownfield site that can be reused by commercial and industrial enterprises.

Arriving at effective methods for disposal of hazardous wastes is difficult because these wastes come in many forms, including solid, liquid, sludge, and gas. Governments regulate hazardous wastes and require their disposal in designated facilities. Hazardous wastes can be stored in sealed containers in the ground or recycled into new products such as fertilizers. The methods and locations used for disposing of hazardous wastes are not the same as those employed in solid waste disposal. Nonhazardous solid wastes or trash can be disposed of in nonsecure landfills, while hazardous wastes should be deposited in secure landfills so they do not contaminate the groundwater.

Background and History

Disposal of waste has existed since ancient cultures burned, recycled, and buried their trash. After World War II, toxic materials were manufactured in greater quantities, and industrialized nations allowed uncontrolled dumping, burning, and disposal of hazardous wastes until the public demanded regulation because of human health and environmental threats. In the United States, Congress charged the Environmental Protection Agency (EPA) with regulating hazardous waste disposal through the Resource Conservation and Recovery Act (RCRA) of 1976, which amended the Solid Waste Disposal Act of 1965. The EPA is authorized to control hazardous wastes from cradle to grave under RCRA, which means regulating generators, transporters, and the facilities involved in treatment, recycling, storage, and disposal.

From the 1940s through the 1960s research showed a relationship between hazardous waste disposal and contamination of groundwater. By employing hydrology studies of underground water movement, scientists were able to pinpoint the sources of hazardous waste contamination. In 1980, the EPA established the Superfund program for the clean up of sites contaminated with hazardous wastes.

How It Works

Manifest Disposal System. In the United States, hazardous waste disposal is governed by the RCRA manifest system. Generators must prepare a form that discloses the type and quality of wastes to be transported to an off-site facility for treatment, storage, recycling, or disposal subject to the Hazardous Materials Transportation Act (HMTA). Because the generator remains liable for proper disposal, a copy of the manifest form, signed by all handlers of the hazardous wastes, is returned to the generator to verify its delivery. However, some wastes are not transported but are treated and disposed of on-site.

Disposal methods for hazardous wastes vary depending on the dangers posed by the wastes. The goal is to remove the characteristics of the wastes that are harmful to human health and the environment. Some methods include treatment, disposal in secure landfills, and incineration.

Treatment. Treatment involves neutralization of chemical, biological, and physical characteristics that make a waste hazardous to the environment. For example, acids that cause corrosion can be neutralized with basic substances, reagents, or through pH adjustment. Cement has also been used to decrease the toxicity of some hazardous wastes through stabilization, often those found in sludge. Industrial hazardous wastes may receive either chemical treatments, such as chlorination, oxidation, and chemical bonding, or the application of physical techniques not limited to distillation and filtration. Medical wastes are considered biohazards that can cause the spread of disease and present different treatment issues. Treatment techniques for these biological wastes include steam sterilization and chemical decontamination before disposal.

Landfill Disposal. Hazardous materials that are not stored on the surface can be disposed of in hazardous waste landfills. The materials must first be sequestered from nonhazardous wastes and treated. Moreover, because hazardous wastes can interact with each other they must be segregated and stored by type before being disposed of in a landfill. The hazardous wastes are then placed in secure storage containers that are buried in landfills with plastic and clay liners that are thicker than the ones used in solid-waste landfills to prevent leaching into the groundwater.

Incineration. Incinerating some hazardous wastes, such as oils and solvents, at high temperatures will reduce the amount of hazardous material through destruction. Although gases released through incineration can generate energy, incinerating facilities must comply with the Clean Air Act. Starved air incineration, which controls the combustion rate of hazardous wastes, is one of the newer technologies that aid in reducing the amount of air pollution caused by incineration. Another treatment method known as pyrolysis may be used to destroy concentrated organic wastes such as polychlorinated biphenyls (PCBs) and pesticides. Pyrolysis is different from high-temperature incineration in that it employs ultrahigh temperatures in the absence of oxygen, often under pressure.

Applications and Products

Energy. Hazardous wastes such as solvents or used oil are often burned directly to produce heat or electricity. This disposal application is regulated throughout the world, and in the United States, the EPA requires the combustion units employed in the burning of hazardous materials to comply with specific standards that prevent harmful air pollution. Some companies, however, have developed proprietary processes that treat hazardous materials using plasma-enhanced waste-recovery systems that turn hazardous wastes into nontoxic, synthetic, gas-alternative energy sources. Unlike direct burning, these new applications claim to destroy all hazardous components that might pollute the air.

Storage. Some hazardous wastes are disposed of through storage. Storage facilities must be able to withstand natural disasters such as seismic events. Storage drums and containers must be secure from fire and water intrusion, and an entire industry has developed to provide appropriate containers that will not leak into the groundwater or explode on impact. Hazardous wastes must first be characterized before they are disposed of in storage containers. Containers used to store hazardous wastes must be designed to accommodate diverse characteristics such as toxicity, corrosivity, and ignitability, and the stored materials should not react with the container or be mixed with other incompatible materials. Storage containers must be sealed and appropriately labeled with the contents and characteristics of the stored hazardous wastes, and a permit is required in the United States to allow for permanent storage. Liquid hazardous wastes, however, are often disposed of in underground injection wells. The EPA regulates the construction, operations, and closure of such wells, which are also subject to regulation under the Safe Drinking Water Act.

Remediation. Many companies specialize in hazardous waste remediation by providing various disposal services and equipment, not limited to catalytic oxidizers and carbon adsorption systems. Remediation includes the reduction and cleanup of hazardous wastewater by using oil-water separators to separate oil and solids from wastewater effluents of petroleum-based industries. Other hazardous waste remediation services include demolition and removal of hazardous materials such as asbestos, removal of leaky fuel tanks, cleanup of contaminated soils, and the construction of slurry walls to aid in the remediation of groundwater that is polluted with hazardous waste. Bioremediation is also a growing field that involves the disposal of medical and laboratory wastes, often by using microorganisms to break down hazardous materials.

Recycling and Reclamation. Recycling and reclamation are important disposal applications because they help reduce hazardous wastes and the amount of raw materials that are consumed. Some materials that may be classified as hazardous wastes can be recycled and used again, such as rechargeable batteries and heating and air-conditioning thermostats. Spent solvents are an example of a product that can be made pure and reused for the same purpose, as can used oil, which can also be processed to create new oil-based products. In addition, the EPA allows some hazardous materials to be treated, recycled, and disposed of on the land in fertilizers or as an ingredient in asphalt. Components of hazardous wastes can also be reclaimed for use in new products. Examples include mercury reclaimed from thermometers, silver from photographic fixers, and scrap metal from auto bodies or manufacturing processes.

Telephones, televisions, audiovisual equipment, computers, computer components, circuit boards, and handheld devices that store music and books are all examples of products that are disposed of by businesses and individual consumers as electronic wastes (e-wastes) when they become obsolete. E-wastes, however, contain hazardous materials such as lead, cadmium, and some precious metals that can be reclaimed and reused. Recycling of e-wastes is an important hazardous waste disposal application throughout the developed world to mitigate the growth of this type of waste.

Hazardous Material (Hazmat) Products. Hazardous waste disposal is not always carried out effectively, so an entire industry has grown out of spills that need to be cleaned up. Hazmat team members will wear different types of hazmat suits, often with ventilators, depending on the characteristics of the hazardous material to be cleaned up. Specially manufactured boots, gloves, and socks are also part of the necessary clothing. Those involved in hazmat-cleanup applications will use spill kits that enable first responders to determine whether the hazardous material presents a chemical, biological, or radioactive hazard. These products are employed in many situations that include not only hazardous material spills but also disposal of illegal drugs and abandoned storage drums and cleanup of any dump site that contains suspicious materials. After the hazardous wastes have been cleaned up and properly disposed of, decontamination is necessary. Decontamination products include temporary shelters, showers, and cleaning solutions.

There are many companies, like BioSAFE Engineering, that provide solutions for handling potentially infectious materials in healthcare, life sciences, and biosafety facilities. Such facilities are identified with biosafety levels (BSL), from the lowest, BSL-1, to the highest, BSL-4. Due to the COVID-19 pandemic in 2020–21, research focused on site-specific decontamination technology that could destroy maximum pathogens.

Careers and Course Work

Hazardous waste disposal involves interdisciplinary coursework such as engineering courses concerning the characteristics and sources of hazardous wastes and their treatment, destruction, and recycling; biology and chemistry classes, especially related to human-health issues and the environment; and law and economics studies that consider disposal regulations and their costs. Certifications necessary for a career in this field include environmental hazardous materials technology and emergency response. Hazmat School in California and Lion Technology in New Jersey offer online hazardous waste training courses and waste audit report training programs.

Career opportunities are growing in this field, including positions with agencies at all levels of government and with waste-management firms and engineering companies involved in transporting, treating, recycling, and disposing of hazardous wastes and remediating and cleaning up sites where there has been contamination. Aspirants can work as hazardous waste technicians, materials managers, and environmental coordinators. Hazardous waste generators, such as utility companies, hospitals, and manufacturers, often hire in-house hazardous waste experts. Educational institutions and laboratories also employ educators and researchers with doctoral degrees in engineering and hazardous waste management.

Those interested in careers as chemical, environmental, sanitary, and sewage engineers will need at least a bachelor's degree to obtain a job as a hazardous waste management specialist. Careers that require a minimum of an associate's degree and some additional training and certifications include workers involved in collecting, transporting, treating, and destroying hazardous wastes, in addition to emergency response and cleanup. Common job titles for hazardous waste workers are hazardous waste technician, field technician, and environmental technician.

Social Context and Future Prospects

Nations must continue to strive for hazardous waste disposal that proactively reduces the amount of hazardous waste and, where possible, recycles these wastes to conserve the consumption of raw materials. Although progress has been made globally in ensuring proper hazardous waste disposal, the funds needed for public education and cleanup of improperly managed hazardous waste sites are not always available. International cooperation is also necessary to resolve several hazardous waste disposal issues. Among these are the disposal of radioactive and nuclear wastes and the exporting of hazardous materials by developed nations to underdeveloped countries that are incapable of proper disposal. More than 137 billion pounds of e-wastes were generated globally in 2023, and that figure is only expected to rise exponentially. Appropriate laws, disposal systems, and international treaties are needed to manage these rapidly growing e-wastes, mostly disposed of in landfills.

Disposal of household hazardous wastes (HHWs), such as used batteries, cleaning products, and medications, continues to be problematic because they contaminate groundwater when disposed of in landfills. Although the United States federal government exempts HHWs from regulation, some municipalities require the separation of household hazardous wastes from other solid wastes for collection or disposal at a municipal facility. Better public education and enhanced laws will help mitigate the damage caused by unregulated HHW disposal.

In the 2020s, the EPA continued to regulate hazardous waste recycling management to encourage the maximum possible reuse of materials. Recycling can help reduce greenhouse gas (GHG) emissions. Research suggested that hazardous waste recycling was also beneficial for industries, as it could increase production efficiency and reduce raw material costs. Innovations in hazardous waste disposal continued as the twenty-first century progressed with a specific focus on reducing the environmental impact. Advanced chemical treatment methods mitigated the environmental damage of hazardous wastes by transforming them into less harmful forms. Bioremediation transformed hazardous wastes into less toxic substances using microorganisms to break them down. Finally, robotic and automated systems reduced the impact of hazardous waste on workers. 

Bibliography

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