The search for safer methods of waste management and disposal has begun. This search is exemplified by the paradigm shift occurring in the field of Waste Management
Philosophy #1 -- Out of sight out of mind: widespread environmental damage, the philosophy persists, and continues to pose serious problems
Philosophy #2 -- Dilute and Disperse (“the solution to pollution is dilution”): First century of Industrial Revolution , no longer suitable for waste disposal; many environments have reached their maximum compensation points
Philosophy #3 -- Concentrate and Contain: the most popular today, very energy intensive and expensive
Philosophy #4 -- Resource Recovery: waste converted to useful material, requires technology, and volumes too large
Philosophy #5 -- Integrated Waste Management: Complex set of alternatives: source reduction, recycling, composting, landfill, and incineration
Solid-Waste Disposal -- primarily an urban problem , common methods include:
On-site Disposal: most common in households (grinding of kitchen food waste), disposal in sewage treatment plant
Composting: a biochemical process, organic materials decompose to humus-like material
Incineration: the reduction of combustible waste to inert residue; burns at high temperatures (900 to 1000 °C)
convert large volume of waste to small volume of ash
combustion used to supplement other fuels for power
Open Dumps: oldest and most common way to dispose of solid waste, without regard to safety, health, or aesthetics
Sanitary Landfills: defined by the American Society of Civil Engineering as a method of solid-waste disposal that functions without creating a nuisance or hazard to public health or safety -- This is an important geological problem.
S. Hughes 2000 Solid Waste Disposal Types of materials or refuse commonly transported to a disposal site. Source: Keller, 2000, Figure 12.1
S. Hughes 2000 Solid Waste Disposal Generalized composition of urban solid waste (by weight) for 1986 and projected for 2000 Material 1986 (%) 2000 (%) Paper 36 39 Yard Waste 20 19 Plastics 7 9 Metals 9 9 Food Waste 9 7 Glass 8 7 Wood 4 4 Other 7 6 (source: Keller, 2000, Table 12.1)
Geologic mapping is critical -- must be at least 10 meters between the base of the landfill and the top of the water table at its shallowest point - this includes anomalous shallow aquifers such as “ perched aquifers ”. An event of high infiltration may cause the main aquifer to become hydraulically connected with the perched aquifer.
Important factors to consider:
Natural filtration of the subsurface - contaminants may be removed from leachate before they reach the water table. Filtration can also occur by ion exchange or sorption.
Dispersion possibilities - migration will occur as a result of both physical and chemical gradients. It is also important to determine subsurface fractures.
Precipitation possibilities - heavy metals may precipitate out of leachate, or will they remain suspended
S. Hughes 2000
S. Hughes 2000 Example #1: Waste disposal site where the refuse is buried above the water table over a fractured rock aquifer . Low potential for serious pollution because leachate is partially degraded by natural filtering as it infiltrates through the unsaturated zone down to the water table. Dispersion of contaminant confined to fracture zones.
Higher water table
Thinner cover material
Cover material has moderate to high hydraulic conductivity
Source: Keller, 2000, Figure 12.2
S. Hughes 2000 Example #2: Solid-waste disposal site where waste is buried above the water table in permeable material with high hydraulic conductivity. Leachate can migrate down to fractured bedrock (limestone) High potential for groundwater pollution -- many open and connected fractures in the rock. Leachate Moves quickly through sand & gravel Enters limestone , transported through open cavities and fractures Has little degradation Source: Keller, 2000, Figure 12.3
Limestone or highly fractured rock quarries , and sand and gravel pits (because they are good aquifer materials)
Swampy areas , unless properly drained
Floodplains , absolutely not acceptable
Areas near coast ; trash or leachate will pollute beaches and coastal marine waters
Any area with high hydraulic conductivity and high WT
Acceptable Landfill Sites:
In rough topography, areas near heads of gullies , where surface water is at a minimum
Clay pits , if kept dry
Flat areas , if a layer with low hydraulic conductivity (aquitard, clay and silt) is present above any aquifer
S. Hughes 2000 Source: Keller, 2000, Figure 12.4 Design of Sanitary Landfills -- complex, with multiple barriers : clay liner, leachate collection system, and a compacted clay cap Idealized diagram of a landfill with a double liner of clay and plastic, and a leachate collection system: Map View Cross Section
S. Hughes 2000 Source: Keller, 2000, Figure 12.6 Monitoring Sanitary Landfills Must begin monitoring the movement of groundwater before operating the site, then continued monitoring of movement of leachate and gases Hazardous pollutants can enter the environment many ways: 1. Gases CH 4 , NH 3 , H 2 S, N 2 go to the atmosphere 2. Heavy metals Pb, Cr, & Fe are retained in the soil 3. Soluble chlorides, nitrates, & sulfates go to groundwater 4-7. More pathways
Hazardous Waste Management -- How did it begin? What events made humans aware of problems?
Rachel Carson’s book Silent Spring
Rachel Carson's book "Silent Spring" discussed the bioaccumulation of DDT (a pesticide) . DDT was discovered in the reproductive tissues of numerous species of birds. This chemical causes thinning of eggshells such that when the female attempts to brood her eggs she ends up crushing them. Ms. Carson's work described for the first time how all things are connected, and clearly demonstrated that the Out of Site, Out of Mind philosophy was no longer valid . Love Canal is located near Niagara Falls, New York . During the 1940s and 1950s indiscriminate dumping of hazardous wastes by companies such as Hooker Chemical Co. occurred. Eventually the site was filled in and sold to the Niagara Falls School District. Although instructed on the nature of the site, and told not to engage in excavation or underground construction, the school district built an elementary school in the area, and a neighborhood of houses grew around it - complete with basements. In the 1970s strange odors could be detected indoors and people began experiencing symptoms of chemically induced illnesses. Investigation by reporter Michael Brown (he won the Pulitzer Prize for this) uncovered the truth and the U.S. government purchased the entire Love Canal site.
Comprehensive Environmental Response, Compensation and Liability Act ( CERCLA ) or SUPERFUND
The Love Canal incident was the catalyst for the passing of the two most important pieces of waste legislation. The first is the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) or SUPERFUND. Although the danger was never as great as the public perceived it to be, Love Canal was the impetus for the passage of CERCLA in 1980. This legislation was designed to provide funds and technical ability for the clean up of hazardous waste sites contaminated by past generation, transport, and disposal activities. CERCLA aims at finding the Potentially Responsible Parties (PRPs) and making them pay for clean up, however funds exist in case no PRPs can be found. Site selection is done by a simple site assessment, after which a priority number is assigned. If the number is high enough the site is placed on the National Priority List (NPL) and becomes a Superfund site. Once CERCLA got underway, it quickly became apparent that a tremendous amount of Superfund sites existed. There were 100 sites on the NPL by 1988. CERCLA also makes emergency provisions for responding to current releases of hazardous substances. In 1994, SUPERFUND was extended by the Superfund Amendments and Reauthorization Act (SARA) . An important part of SARA is Title III - known as the Emergency Planning and Community Right-to-know Act (EPCRA). Superfund was extended again in 1994 by the Superfund Reform Act.
CERCLA has a number of limitations. Most of its funds have been soaked up by legal battles attempting to assign liability and responsibility. Also, CERCLA's testing methods may not be stringent enough. Unfortunately this law deals with such huge problems that it is not possible to be rigorous. A number of the CERCLA treatment technologies are in themselves environmentally disruptive. Methods such as excavation and removal of contaminated soil, structures etc. are widely used in order to minimize time and money expenditures. Of course, they then have to face the problem of what to do with the CERCLA material!
Resource Conservation and Recovery Act ( RCRA )
The second of the two major pieces of waste legislation also stemmed from the Love Canal incident. The RESOURCE CONSERVATION AND RECOVERY ACT (RCRA) passed in 1976 in response to the problem of determining liability and responsibility at Love Canal. The Act was intended to provide a regulatory framework for waste management that would prevent this type of uncertainty in the future. It consists of comprehensive legislation dealing with all aspects of current, ongoing waste production and disposal - particularly of hazardous material. It also assigns "CRADLE-TO-GRAVE" responsibility to generators of hazardous wastes.
S. Hughes 2000 Source: Keller, 2000, Figure 12.8 EPA - National Priorities List = Superfund Sites Environmental impacts at Superfund sites (NPL) and some of the pollutants encountered at the sites: Question to think about: What does Cradle-to-Grave mean in terms of Hazardous Waste Management?
On-site processing to recover byproducts with commercial value
Disposal by secure landfill
Disposal by deep-well injection
Review Table 12.3 (handout) to compare hazardous waste reduction technology in terms of treatment and disposal
What waste treatment technologies are important today?
S. Hughes 2000 Source: Keller, 2000, Figure 12.9 Secure Landfill -- Confine the waste to a particular location, control the leachate that drains away, collect and treat the leachate, control leaks The figure shows a secure landfill for hazardous chemical waste ; Note impervious liners & drainage system; monitoring in vadose zone is important -- involves collection of soil water.
S. Hughes 2000 On-Site Disposal -- The most common disposal method. Drains, sewers, windows, pits and so on are all used to get rid of unwanted substances. Both hazardous and non-hazardous wastes find their way into the environment by this route. Composting -- The decomposition of organic matter by biological organisms. On a household scale composting can significantly reduce the amount of garbage. Composting can also be done on a municipal scale . For example, in 1983 the VAM recycling and waste treatment facility in Wijster, Netherlands produced 125,000 tons of quality compost from discarded municipal organic waste! Land Application -- Desirable treatment for some biodegradable industrial wastes (microbial degradation), usefulness is determined by biopersistence of the waste Surface Impoundment -- Use excavations and natural topographic depressions, natural soils, prone to leakage, NOT good for hazardous chemicals
LEACHATE - Leachate is a combination of infiltrated precipitation and any liquids squeezed from the waste as it naturally compacts. Leachate will percolate to the base of land disposal sites due to the influence of gravity. Leachate can carry particulate matter, pollutants, biological contaminants and other constituents with it. Leachate will travel through the subsurface following the same flow direction as groundwater. Leachate is a potentially major source of pollution. As such all land based disposal facilities must incorporate a leachate collection and disposal system into their designs. Also liners and covers must be added so as to minimize infiltration into the waste site thereby minimizing leachate production or escape.
LINER - Generally there are several layers of liners at the base of a land disposal site. Layers consist of compacted clay alternating with plastic. Leachate collection systems are placed just below the first and second (in case the first one is breached) liner layers. The purpose of the liner is to prevent leachate from escaping into the subsurface.
CAP/COVER - Caps and covers are constructed (starting at the waste and working outward) of compacted, low permeability clay. This is followed by a flexible plastic liner (theoretically impermeable). Next comes a drainage layer designed to transport surface water away from the waste disposal site. Finally, this is followed by a layer of earth and then some type of vegetative cover.
S. Hughes 2000 Source: Keller, 2000, Figure 12.10 Deep-well Disposal -- In rock (not soil), isolated from freshwater aquifers; waste is injected into a permeable rock layer hundreds to thousands of meters below the surface. Deep-well injection of oil-field brine has been important to control water pollution in oil fields for many years. Deep-well injection system -- disposal in sandstone or fractured limestone capped by impermeable rock and isolated from fresh water. Monitoring wells are a safety precaution.
S. Hughes 2000 Deep-well Injection The underground injection of liquid wastes has been occurring in the United States for many decades. In general, this technique is used to dispose of wastes deep below the earth's surface in well-confined geologic formations . Deep well injection directly introduces liquids into a deep aquifer in the subsurface environment via pressurized wells .
Deep-well Injection -- Multiple factors must be considered when selecting a disposal well site:
Aquifer response to injection rates, pressures, type of waste
The location of confining structures above and below
Site bounded vertically and laterally by confining strata
The location of faults, fracture zones , patterns of seismicity
The location of any old conduits between aquifer layers
Physical and chemical character of the waste
Pretreatment of the waste may be required in order to avoid system clogging, corrosion of well casings or other problems
Aquifers with low pressure head , high transmissivity , and high permeability are preferred
S. Hughes 2000
S. Hughes 2000 Monitoring Disposal Wells -- Essential part of any disposal system; important to know where wastes are going, how stable, how fast they migrate, especially if waste is toxic . How liquid waste might enter a freshwater aquifer: Source: Keller, 2000, Figure 12.11
S. Hughes 2000 Incineration -- ”Thermal treatment”, is the high temperature reduction of wastes via combustion. Incineration can attain a 75-95% reduction in waste mass, and can destroy hazardous pollutants with efficiencies as high as 99.99%. A wide variety of thermal treatments exist. Plasma Furnace -- Used to treat hazardous wastes. Operate at incredibly high temperatures ( 8,000-10,000 degrees Celsius ) using gaseous Argon, and everything is atomized. Gaseous Argon is injected into the incinerator and then spun by a radio frequency coil until it reaches operating temperatures. A spray of hazardous waste is then injected via a nebulizer tube, and the combustion reaction is allowed to occur. Drawbacks are that they can only handle small amounts of waste at any one time, and they are time consuming (in terms of operation and maintenance) and expensive. Plasma furnaces are extremely effective however if they are used correctly.
S. Hughes 2000 Source: Keller, 2000, Figure 12.12 Incineration of Hazardous Waste -- considered to be a waste treatment rather than a waste disposal method. High-temperature incinerator system to burn toxic waste:
S. Hughes 2000 Source: Keller, 2000, Figure 12.13 Environmental Problems with Disposal What are some of the paths that pollutants may take? Examples of how land disposal and treatment methods of managing hazardous waste may contaminate the environment :
S. Hughes 2000 Source: Keller, 2000, Figure 12.14 Radioactive Waste Management For waste disposal, radioactive waste is grouped into two general categories: Low-level and High-level radioactive waste ; also mine tailings, which are highly radioactive, must be considered hazardous. Nuclear Fuel Cycle U 235 enrichment Uranium mines and mills -concentrate ore -dispose of tailings Fabricate fuel assemblies Recovered uranium Reprocessing Plant Plutonium Reactor Low-level wastes Spent fuel High-level solid waste Federal repositories - geologic disposal Commercial burial
S. Hughes 2000 "This we know: the earth does not belong to man, man belongs to the earth. All things are connected like the blood that unites us all. Man did not weave the web of life, he is but a strand in it. Whatever he does to the web he does to himself." Chief Seattle, 1852
S. Hughes 2000 Terms for Understanding anaerobic digester CAA cap/cover CERCLA composting cradle-to-grave CWA deep well injection generator hazardous waste heavy metals incineration Industrial Ecology Integrated Waste Management landfill leachate liner Love Canal p oint source pollution non-point source pollution NPL ocean dumping on-site disposal RCRA recycle sanitary landfill SARA secure landfill soluble Superfund urban runoff volatile waste waste disposal waste management zero tolerance