Waste Management. Waste Management

Transcription

1 Waste Management Chapter 12 in textbook (Keller, 2000) For this section, and all sections in this course, look up and study all concepts and terms in various resources: other textbooks library books journal articles websites (in addition to the links in this presentation) NOTE: Always be prepared to discuss any of the concepts in class. Focus on highlighted terms. Diagrams in this presentation are from various sources: Keller (2000) textbook Idaho Virtual Campus -- Environmental Geology course others by S. Hughes Waste Management What is the need for waste management? On Staten Island, New York, a mountain of trash is growing, entirely manmade. Each day: 11,000 tons of municipal and corporate waste disposed of at Fresh Kills Landfill Facility: 3,000 acres (>1200 ha), and by the year 2005 the mountain of trash is expected to reach 150 to 200m New landfills are constructed each year; some are many kilometers away from where the trash was generated. What is the greatest contributor (by volume) to solid waste at a landfill? Answer: 1

2 Waste Management Concepts and Problems Many people live in areas where concentration of toxic pollutants exceeds standards (e.g. 25% of people in Russia) In 1991, 90% of countries had uncontrolled dumping of industrial hazardous waste, >60% had hazardous chemicals disposed of in uncontrolled sites Urban areas produce more waste than there is space for disposal (1/2 of U.S. cities running out of landfill space) and the costs for treatment and disposal are increasing dramatically Siting of new landfills depends on: favorable environment for disposing waste cost of land, transportation and disposal social justice -- economic and social status of citizens environmental justice -- healthy disposal Resources are depleted, health problems are growing, and widespread environmental damage is occurring Waste disposal sites may become the mines of the future. Philosophy of Waste Disposal and Management 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 2

3 Integrated Waste Management (IWM) Trend to develop new methods of waste management that will not cause health problems or become a nuisance waste products = resources out of place Reduce, Recycle, Reuse -- the three Rs of IWM; difficult to have a balance of all three, also add Eliminate to the list Technological Advances -- increase the efficiency of manufacturing processes, minimize waste generation Resource Recovery -- reuse and recycling is on the rise Sequential Land Use -- establish new developments over old Alternative Methods of Waste Treatment NOTE: ONE THIRD of all waste in the United States is packaging! Materials Management -- Part of IWM, but provides a new goal: Zero Production of Waste Eliminate subsidies for extracting virgin materials (timber, minerals, oil, etc.) Establish green building incentives that use recycled materials in new construction Establish financial penalties for production of products that do not meet objectives of material management Establish financial incentives for industrial practices that benefit the environment by enhancing sustainability Provide incentives for producing new jobs in technology of materials management and practice of reducing, recycling and reusing resources 3

4 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. Solid Waste Disposal Types of materials or refuse commonly transported to a disposal site. Source: Keller, 2000, Figure

5 Solid Waste Disposal Generalized composition of urban solid waste (by weight) for 1986 and projected for 2000 Material 1986 (%) 2000 (%) Paper Yard Waste 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) Sanitary Landfills Sanitary Landfills Engineering principles used to: confine waste to smallest practical area reduce waste to smallest practical volume cover waste with layer of compacted soil (or tarps) each day (finishing cover is ~50 cm or more of compacted clayrich soil) Two types of sanitary landfills: area landfill on relatively flat site depression landfill in natural or artificial gullies or pits NOTE: Compaction and subsidence will continue after site is closed; any further development must be able to accommodate these potential problems. Potential Hazards: leachate -- obnoxious, highly concentrated mineralized liquid capable of transporting bacterial pollutants uncontrolled production and escape of methane gas 5

6 Sanitary Landfills -- Site Selection Best sites have natural conditions to ensure reasonable safety in disposal of solid waste: little (or acceptable) pollution of groundwater and surface water. Must consider: climate, hydrology, geology, & human conditions (or combinations of all) Factors controlling the feasibility of sanitary landfills: Topographic relief Location of the Groundwater table Amount of precipitation Type of soil and rock Location of the disposal zone in the surface-water and groundwater flow system NOTE: The best sites are in arid regions, above water table. Sanitary Landfills -- Site Selection Arid Regions Relatively safe, regardless of whether burial material is permeable or impermeable, little or no leachate. Humid Regions Some leachate always produced, need to establish acceptable level of leachate production Need to consider local water use, local regulations, and ability of natural hydrologic system to disperse, dilute and degrade the leachate to make harmless Most desirable to bury waste above water table in clay and silt soils having low permeability Use substrate as a natural filtering system, even if water table is high (typical in humid climate) NOTE: It is very important to consider the geology of the landfill site, type of aquifer, types of soils, etc. 6

7 Sanitary Landfills -- Site Selection 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 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. Problems if: Higher water table Thinner cover material Cover material has moderate to high hydraulic conductivity Source: Keller, 2000, Figure

8 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 Sanitary Landfills -- Site Selection Guidelines Poor or Unacceptable Landfill Sites: 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 8

9 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 Source: Keller, 2000, Figure 12.4 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: Source: Keller, 2000, Figure 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 9

10 Hazardous Waste Management ~1,000 new chemicals created and marketed each year ~50,000 chemicals are currently on the market Many are beneficial to humans, tens of thousands are classified as definitely or potentially hazardous to human health The U.S. generates more than 150 metric tons of hazardous waste each year Uncontrolled dumping in the past, and illegal dumping in the present has polluted soil and groundwater: Barrels of chemical waste eventually corrode Source: Keller, 2000, Figure 12.7 Liquid chemicals often dumped into unlined ponds Liquid waste dumped illegally in deserted fields or along dirt roads Hazardous Waste Management Examples of products in use and the potentially hazardous waste generated. Products Used Plastics Pesticides Medicines Paints Oil, gasoline, etc. Metals Leather Textiles Source: Keller, 2000, Table 12.2 Potential Hazardous Waste Organic chlorine compounds Organic chlorine compounds, organic phosphates Organic solvents and residues, heavy metals (e.g. Hg and Zn) Heavy metals, pigments, solvents, organic residues Oil, phenols, organic compounds, heavy metals, ammonia salts, acids, caustics Heavy metals, fluorides, cyanides, alkaline and acid cleaners, solvents, pigments, abrasives, plating salts, oils, phenols Heavy metals, organic solvents Heavy metals, dyes, organic chlorine compounds, solvents 10

11 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. The Love Canal incident 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 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 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. 11

12 Limitations of CERCLA 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. EPA - National Priorities List = Superfund Sites Environmental impacts at Superfund sites (NPL) and some of the pollutants encountered at the sites: Source: Keller, 2000, Figure 12.8 Question to think about: What does Cradle-to-Grave mean in terms of Hazardous Waste Management? 12

13 Hazardous Chemical Waste Options for Management Recycling On-site processing to recover byproducts with commercial value Microbial breakdown Chemical Stabilization High-temperature decomposition Incineration 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? Secure Landfill 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. Source: Keller, 2000, Figure

14 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 USEFUL DEFINITIONS USEFUL DEFINITIONS 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. 14

15 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. Source: Keller, 2000, Figure 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. 15

16 Deep-well Injection -- Disposal wells use high pressures to overcome existing lithologic and hydrostatic forces in deep aquifers, thereby forcing the aquifer to accept waste loads. U.S. Federal regulations recognize 5 types of disposal wells, each with their own particular guidelines: CLASS I WELLS - used for disposal of hazardous and non-hazardous industrial or municipal wastes. CLASS II WELLS - used for injection of oil field brines and other hydrocarbon wastes. CLASS III WELLS - used for solution mining processes. CLASS IV WELLS - those which historically disposed of radioactive wastes (this is no longer done). CLASS V WELLS - used for any activity not mentioned above, such as geothermal steam mining operations. NOTE: A major problem with deep well injection is that it can cause earthquakes! 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 16

17 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 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. 17

18 Incineration of Hazardous Waste -- considered to be a waste treatment rather than a waste disposal method. High-temperature incinerator system to burn toxic waste: Source: Keller, 2000, Figure 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: Source: Keller, 2000, Figure

19 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 Plutonium -concentrate ore Recovered uranium -dispose of tailings Fabricate fuel assemblies Reprocessing Plant High-level solid waste Federal repositories - geologic disposal Source: Keller, 2000, Figure Spent fuel Reactor Low-level wastes Commercial burial "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,

20 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 point 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 20