Hazardous waste is waste that poses substantial or potential threats to public health or the environment (see Table C2 (“a”, “b”, “c”, “d”)). In the United States, the treatment, storage, and disposal of hazardous waste are regulated under the RCRA. Hazardous wastes are defined under RCRA in the Title 40 CFR 261 where they are divided into two major categories: characteristic wastes and listed wastes.
- Characteristic hazardous wastes are materials that are known or tested to exhibit one or more of the following four hazardous traits:
- ignitability
- reactivity
- corrosivity
- toxicity
- Listed hazardous wastes are materials specifically listed by regulatory authorities as hazardous wastes which are from nonspecific sources, specific sources, or discarded chemical products (Shibamoto et al. 2007).
The requirements of RCRA apply to all the companies that generate hazardous waste as well as those companies that store or dispose hazardous waste in the United States. Many types of businesses generate hazardous waste. Dry cleaners, automobile repair shops, hospitals, exterminators, and photo‐processing centers may all generate hazardous waste. Some hazardous waste generators are larger companies such as chemical manufacturers, electroplating companies, and oil refineries.
These wastes may be found in different physical states such as gaseous, liquids, or solids. 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 required.
Worldwide, the United Nations Environmental Program estimated that more than 400 million T of hazardous wastes are produced universally each year, mostly by industrialized countries. About 1% of this is shipped across international boundaries, with the majority of the transfers occurring between countries in the Organization for the Economic Cooperation and Development. One of the reasons for industrialized countries to ship the hazardous waste to industrializing countries for disposal is the rising cost of disposing of hazardous waste in the home country (Orloff and Henry 2003).
Hazardous Wastes in the United States of America
A US facility that treats, stores, or disposes of hazardous waste must obtain a permit for doing so under the RCRA. Generators and transporters of hazardous waste must meet specific requirements for handling, managing, and tracking waste. Through the RCRA, Congress directed the 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 that are broader in scope than the federal regulations. Furthermore, RCRA allows states to develop regulatory programs that are at least as stringent as RCRA and, after review by EPA, the states may take over responsibility for the implementation of the requirements under RCRA. Most states take advantage of this authority, implementing their own hazardous waste programs that are at least as stringent, and in some cases are more stringent than the federal program.
Hazardous Waste Mapping Systems
The US government provides several tools for mapping hazardous wastes to particular locations. These tools also allow the user to view additional information.
- TOXMAP is a Geographic Information System from the Division of Specialized Information Services of the United States National Library of Medicine (NLM) that uses maps of the United States to help users visually explore data from the USEPA’s Toxics Release Inventory and Superfund Basic Research Programs. This is a resource funded by the US federal government. TOXMAP’s chemical and environmental health information is taken from NLM’s Toxicology Data Network and PubMed, and from other authoritative sources.
- The USEPA “Where You Live” (Chaudhary and Rachana 2006) allows users to select a region from a map to find information about Superfund sites in that region.
Universal Wastes
Universal wastes are a special category of hazardous wastes that (in the United States):
- generally pose a lower threat relative to other hazardous wastes that 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 stringent regulatory requirements. Small quantity generators of universal wastes may be classified as “conditionally exempt small quantity generators” which release them from some of the regulatory requirements for the handling and storage of hazardous wastes. Universal wastes must still be disposed of properly at a regional or county landfill facility.
Final Disposal of Hazardous Waste
Historically, some hazardous wastes were disposed of in regular landfills. This resulted in unfavorable amounts of hazardous materials seeping into the ground. These chemicals eventually entered to natural hydrologic systems. Many landfills now require countermeasures against groundwater contamination. For example, a barrier has to be installed along the foundation of the landfill to contain the hazardous substances that may remain in the disposed waste. Currently, hazardous wastes must often be stabilized and solidified in order to enter a landfill and must undergo different treatments in order to stabilize and dispose them. Most flammable materials can be recycled into industrial fuel. Some materials with hazardous constituents can be recycled, such as lead acid batteries.
Recycling
Some hazardous wastes can be recycled into new products. Examples may include lead‐acid batteries or electronic circuit boards. When heavy metals in these types of ashes go through 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, while also recycling the safe product.
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 five 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.
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