This is the ninth lesson in the independent learning correspondence course on municipal solid waste (MSW) landfills. One lesson in this 12-part series is being published in Waste Age magazine each month throughout the year.
If you are interested in taking the course for two continuing education credits (CEUs), send a check (payable to the University of Wisconsin) for $149 to Phil O'Leary, Department of Engineering Professional Development, University of Wisconsin, 432 North Lake Street, Madison, WI 53706. Phone: (608) 262-0493. E-mail: [email protected] Website: www.wasteage.com.
Course registration can occur at any time until December 2006.
To understand the factors influencing disposal options for certain wastes.
To understand the process for determining whether waste is hazardous.
To understand the trend toward recycling, rather than disposing of, these special waste types.
Historically, as landfill regulations tightened and costs for licensed solid waste facilities grew, certain waste types began being handled and disposed of differently than municipal solid waste (MSW). These waste types, often referred to as special wastes, were managed separately from the traditional waste stream because of their high volume or perceived lower environmental risk. While regulations managing all wastes have become more consistent nationwide, many states still allow some special wastes to be disposed of differently than MSW.
Handling and disposal approaches for special wastes fall into three categories. First, certain high-volume wastes often are disposed of in facilities separate from municipal waste landfills because of the need to guarantee independent disposal capacity, such as for electrical power plant ash, or because of a lower perceived risk to the environment, such as for construction and demolition (C&D) debris [See “C&D Debris in Perspective” on page 69]. Second, some materials present an especially great hazard to health and the environment. Legally termed “hazardous waste,” this waste type must receive special handling and disposal. Finally, because of the risks workers face when handling some materials, special precautions are taken to avoid worker exposures. Infectious waste and asbestos fall into this category.
While regulations for handling these three special waste streams vary from state to state, some guidelines can be followed in assessing handling and disposal options. Local and state regulatory officials also should be consulted to determine waste regulations for a specific region.C&D Waste
The United States produces an enormous quantity of C&D debris from a variety of materials including road paving waste to razed buildings [See “Estimated Building-Related C&D Debris Generation” on page 72]. Often, the material is fairly inert and bulky.
Because C&D material generally is perceived to present less of a threat to the environment than normal MSW, many states do not require small demolition waste landfills to meet the strict liner and leachate collection system requirements found in regular MSW landfills. Managing C&D waste separately saves MSW landfill space as well as tipping fee costs for C&D debris collection companies.
Designs for C&D debris landfills vary. Normally, sites are not required to have an engineered liner system or leachate collection system, but they must be placed in an environmentally sound location and be capped with a layer of impermeable soil or top soil, and be seeded. In some states, groundwater monitoring also is required.
The less-than-state-of-the-art requirements for C&D debris disposal have been used for some time. However, some recent studies indicate that leachate from C&D debris landfills may contain hazardous components [See “Comparing the Leachates: C&D Laboratory Full-Scale Full-Scale C&D Waste” on page 73].
Research concerning C&D leachate quality continues to be conducted at institutions, such as the University of Florida Solid and Hazardous Waste Center. If leachate quality from both C&D landfills and MSW landfills are comparable, regulatory officials may scrutinize the materials that go into these sites, or they may require C&D landfill designs that are more similar to MSW landfills.Combustion Ash
Industrial boilers and their emission control systems produce a variety of residues. By far, the largest quantity is bottom ash, the unburned and nonburnable materials that drop from the bottom of the combustor at the end of the burning cycle.
The process also produces a lighter emission known as fly ash. Fly ash consists of gaseous components and particulates that result from the chemical decomposition of burnable materials, or are nonburned (or partially burned) materials drawn upward by thermal air currents in the incinerator.
Fly ash normally comprises only a small proportion of the total volume of residue from an industrial boiler — quantities range from less than 1 percent to more than 15 percent of the total ash. Distribution of bottom and fly ash is largely influenced by the combustion unit type. Excess air systems produce the most fly ash; controlled air units produce the smallest amounts.
Emission control devices such as electrostatic precipitators and baghouses do not rely on added materials to control pollutants. Some, however, including dry scrubbers, inject absorbing materials to capture and neutralize acid gases and other pollutants. Such a system could use a fine spray of either calcium- or sodium-based alkaline slurry.
In these systems, the resultant pollutant/slurry mixture is known as scrubber product. Scrubber product must be properly handled to avoid environmental pollution. Many ash producers, especially electric utilities, construct landfills designed solely to accept ash because they need to dispose of many tons of ash. These sites often are referred to as monofills.
Because the landfill's input is known, a monofill design may be simpler and therefore less costly than a normal MSW landfill. For example, because ash is inert, methane collection is unnecessary. Also, owning and operating a monofill ensures access to a licensed disposal site throughout the facility's life.Determining Whether Waste Is Hazardous
Normally, a waste generator must determine whether waste is legally hazardous or not. However, if legally hazardous waste is disposed of in a facility not designed for that purpose, the landfill owner and operator may share liability.
U.S. Environmental Protection Agency (EPA), Washington, D.C., regulations classify waste as legally hazardous if it is listed as hazardous in EPA tables or if the waste exhibits certain defined characteristics of ignitability, reactivity, corrosivity or toxicity.
Waste is ignitable if it has a flash point less than 142 degrees Fahrenheit, or 60 degrees Celsius. Waste is reactive if it is normally unstable or reacts violently with water. Waste is corrosive if it has a pH less than or equal to 2, or greater than or equal to 12.5 (strong acids and bases).
To determine whether waste is toxic, the EPA uses a test known as the toxicity characteristic leaching procedure (TCLP). TCLP determines the tendency of waste to leach certain pollutants into the groundwater. Testing procedures expose the waste material to an acidic environment in an attempt to predict which materials could ultimately be released into the groundwater. If materials released in the test exceed levels in the TCLP table, the waste is considered to be legally hazardous and must be handled as such. For some waste, pretreatment or treatment also may be used to lower pollutant concentrations below regulatory limits. Local regulatory officials can provide guidance.Disposing Hazardous Waste
Hazardous waste landfills are based on the same design as MSW landfills. These facilities use a highly impermeable liner, a leachate collection system, a groundwater and gas monitoring system, and careful siting and operation procedures to protect the environment.
However, a hazardous waste landfill also is designed with more protection. For example, today, a hazardous waste landfill would have a double composite liner, each liner equipped with a separate leachate collection system to ensure that no leachate escapes into the environment [See Double Liner and Leachate Collection System” diagram above].
Groundwater monitoring systems around the site also are extensive to ensure that any contaminants released by the site are detected before they can enter neighboring water supplies.
Operations at hazardous waste sites are stricter, too. For instance, liquids are prohibited. Instead of mixing loads of incoming waste, as is common at municipal waste landfills, wastes at hazardous waste landfills often are characterized by type and disposed of in a grid pattern to keep incompatible waste separate. Careful waste placement and the use of a grid system reduces the risk of underground chemical fires and explosions.
The distinction between designs for hazardous waste landfills and solid waste landfills has blurred. Resource Conservation and Recovery Act (RCRA) Subtitle D standards now require double liners for landfills, and some designs use a liner with a full site lysimeter system to ensure groundwater protection and contaminant detection. To increase public acceptance and confidence in a landfill system's ability to protect the environment, landfill designs with multiple liner systems for disposing of both hazardous and solid waste likely will continue to be used and improved.Special Waste Handling Requirements
Some wastes do not present special risks once they are properly disposed of in a landfill. However, waste may present health risks to workers and the public if it is improperly handled prior to disposal. Consequently, many states require some wastes be specially handled and transported. New federal and state employee right-to-know and hazard communication regulations are making employee safety and training a priority. For instance:
Incinerator Ash: Fly and bottom ash contain pollutants that could cause respiratory problems among employees who handle this residue. In some states, special precautions minimize employee exposure risk, including wetting the ash to reduce dust and using face masks when handling residue in a dry form. Transporting ash to disposal facilities also may be regulated. And, covered vehicles often are required. If the ash is hazardous, special regulations apply.
Asbestos: Asbestos is a health hazard if inhaled. To protect workers, many states require asbestos be disposed of at the base of a landfill's active working face into a specific excavated disposal trench. Then, the waste is covered immediately with a minimum number of feet of waste or soil prior to compaction. To avoid disturbing the disposed asbestos, some states also require that asbestos disposal areas do not coincide with previous asbestos disposal areas and are not located near proposed future landfill construction.
Infectious waste: To protect workers, some states now require infectious waste — that may contain human pathogens and normally is generated at hospitals and clinics — be incinerated or sterilized prior to disposal. This precaution renders the waste noninfectious and protects site workers from exposure to human pathogens.
Nevertheless, with an aging society, increasing quantities of infectious waste may be entering landfills through normal solid waste, as many people administer medications at home. While hospitals and other health care facilities are required to ensure processing of infectious waste streams, it would be nearly impossible to police normal solid waste volumes to ensure that syringes, bandages and other types of medical waste are noninfectious.
To protect workers and the public, many states require infectious waste be transported in covered, leak-proof vehicles, with the waste stored in rigid, puncture-proof containers. Vehicles and storage containers must be properly labeled.Recycling Special Wastes
Given the huge volume of power plant ash, C&D waste and other special wastes produced in the United States, significant effort is being put into finding ways to recycle or reuse these materials. For example, “green building,” construction reuses as much demolition waste from an old building as possible in new building designs. Wood, bricks, furniture and other materials now are being separated and reused, instead of being landfilled.
Great strides have been made in using foundry sand for various road construction. Likewise, combustion ash is being used as aggregate in road construction or in building construction. Some paper mill sludge is being land spread as a soil amendment, as is sewage sludge. Effort is underway nationally to beneficially reuse as much high-volume waste as possible to reduce landfill needs and to save money. This trend is expected to continue.
Phil O'Leary and Patrick Walsh are solid waste specialists with the University of Wisconsin-Madison.
“Characterization of Building Related Construction and Demolition Debris in the United States,” EPA 530-R-98-010 (June 1998).
Townsend, T. et. al., “Continued Research Into the Characteristics of Leachate From Construction and Demolition Landfills.” (Report 00-04) Florida Center for Solid and Hazardous Waste Management (July, 2000).
U.S. Environmental Protection Agency website http://www.epa.gov/epaoswer
Universe of Non-Hazardous Wastes Subject to Regulation under Subtitle D of RCRA
- Building related waste
- Roadway-related waste
- Bridge-related waste
- Landclearing and inert debris waste
Municipal solid waste
Industrial nonhaz. process waste
Oil and gas waste
Trees & brush
Source: “Characterization of Building-Related C&D Debris in the U.S.,” U.S. EPA OSW
|*C&D debris managed on-site should, in theory, be deducted from generation. Quantities managed on-site are unknown.|
|Source: “Characterization of Building-Related C&D Debris in the U.S.,” U.S. EPA OSW|
|Parameters||SKBa||WMIb||Class III Landfill in Florida||C&D Landfill Leachatec||Test Cell Leachate|
|a. Source: NADC (1994)|
|b. WMI (1993)|
|c. Mean values in Melendez (1996)|
|d. Total organic content concentration.|
“Continued Research into the characteristics of leachate from construction and demolition waste landfills” (Report #00-04)
Florida Center for Solid and Hazardous Waste Management (July 2000)
Timothy G. Townsend, Principal Investigator
Department of Environmental Engineering Sciences
University of Florida
State University System of Florida