Waste Disposal. Chapter 15

Transcription

1 Waste Disposal Chapter 15

2 Some Facts In 1996, U.S. residents, businesses, and institutions produced more than 209 million tons of MSW, which is approximately 4.3 pounds of waste per person per day, up from 2.7 pounds per person per day in 1960 = mass of Statue of Liberty every 5 years United States has 8% of world population Consume 1/3 rd of World s resources Produces ½ of World s garbage

3 Handled on site Not toxic Not toxic Areas of concern

4 1991 data Paper: 50%

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6 Municipal Waste Open Dump Sanitary Landfill Incineration Ocean dumping

7 Open Dump Unsanitary, draws pests and vermin, harmful runoff and leachates, toxic gases Still accounts for half of solid waste Several thousand open dumps in the USA

8 Sanitary Landfill Sanitary Landfill Layer of compacted trash covered with a layer of earth once a day and a thicker layer when the site is full Require impermeable barriers to stop escape of leachates: can cause problem by overflow Gases produced by decomposing garbage needs venting 1 acre/10,000 people: acute space problem: wastes piling up over 150 million tons/year; # of landfills down from 8000(1988) to 3091(1996) NIMBY, NIMFYE, NIMEY, NOPE NJ ships >5 million tons of waste every year

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11 Incineration Solves space problem but: produces toxic gases like Cl, HCl, HCN, SO 2 High temp furnaces break down hazardous compounds but are expensive ($75 - $2K/ton) Heat generated can be recovered: % of waste burnt Japan 67%, Switzerland 80%, USA 6% North Little Rock, AK saving $50K in heating cost and reducing landfill requirement by 95% How many MSW combustors exist in the United States? In 1996, 110 combustors with energy recovery existed with the capacity to burn up to 100,000 tons of MSW per day.

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13 Ocean Dumping Out of sight, free of emission control norms Contributes to ocean pollution Can wash back on beaches, and can cause death of marine mammals Preferred method: incineration in open sea Ocean Dumping Ban Act, 1988: bans dumping of sewage sludge and industrial waste Dredge spoils still dumped in oceans, can cause habitat destruction and export of fluvial pollutants

14 Reducing Waste Incineration, compacting Hog feed: requires heat treatment Composting: requires separation of organics from glass and metals Recycling and Reusing Recycle of glass containers: 5 million tons Plastic: marked by types for easy recycling Converted into Fibers, trash bags, plastic lumber, fill for pillows, insulation etc Junked cars: kg of plastics: soon to be recycled

15 In 1996, recycling of solid waste in the United States prevented the release of 33 million tons of carbon into the air roughly the amount emitted annually by 25 million cars. 1 ton of newspaper=18 trees, 3 m 3 of landfill, 60% less energy. Govt recycling saving 223,000 tons, 4 million trees, $7.4 million Auto Steel Aluminum Paper & Yard Glass Plastic Tires Batteries Cans Packaging Paperboard waste container container

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17 Waste Exchange One persons waste can be another persons raw material Fluorite from Al smelter in MD Isopropyl alcohol = cleaning solvent Nitric Acid from Electronic Industry = high grade fertilizer Spent acid of steel industry = control for H 2 S

18 Liquid Waste Sewage Highly toxic Industrial Waste & Used Oil Dilute and Disperse Concentrate and Contain Secure Landfill Sealed drums to be put in impermeable holds with monitoring wells to check for leakage: does not work Deep well Disposal Pumping in deep porous layer bounded by impermeable formations, well below water table $1 million to drill, $15-20/ton afterwards Restricted by geological considerations, can trigger earthquakes

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21 Story of Love Canal A ditch 20m wide, 3m deep and 1km long 1890: Built near Niagara falls for hydro-power 1905: Hooker Electrochemical established 1942: Hooker buys the site for waste disposal, 20,000 tons of toxic chemical dumped in 10 yr 1953: site bought by Niagara School board for $1, Hooker absolved of any future damage 1977: study shows toxic effects in adjoining homes,>40 toxic chemicals identified 1978: Health advisory, 100 families to be shifted 1980: remedial measures taken, EPA study shows chromosome defects in residents, President Carter declares emergency, provides federal aid 1981: Over 500 families moved out, hundreds waiting for aid EPA estimate: 30,000 hazardous waste sites in US, only 10% of hazardous wastes properly disposed, 300 million tons generated each year

22 Sewage Treatment Individual scale Settling tank (solids settle and are broken down) Leaching field: receives liquids from septic tank through porous pipes. Bacteria and oxygen breaks down organics and disease causing germs Should have soil layer = 60 cm below 150cm above Should not be within 15m of any water body 0.5 to 1 acre per dwelling

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24 Municipal Sewage Treatment 75% of US population served by sewage system and <5% releases untreated sewage Primary treatment: removal of solids Secondary treatment: biological Bacteria and fungi breaks down organics Chlorinated to kill germs, can form chloroform which is carcinogenic Tertiary treatment: Filtration and chemical treatment: expensive Sludge is a by-product and is rich in organics and nutrients

25 Radioactive Waste Disposal Isotopes with short half-lives are gone quickly, those with long half-lives will decay too little Low level wastes: 90% of all radioactive wastes 20 temporary and 6 commercial disposal sites States to take care of their low level waste High level wastes e.g., spent nuclear fuel rods Should be so disposed as to cause less than 1000 death in 10,000 years

26 High Level Waste Depository Rocketing to sun Under Antarctica Ice sheet Subduction Zone Sea bed disposal Bedrock caverns Granites, basalt, tuff, shale, salt caverns Salt: High melting point, impermeable in dry condition, self-sealing, cheap resource No permanent high level waste repository yet

27 Requirements for a radio-active waste disposal system Design and Fabricate a System that will Last thousands of years longer than recorded human history Be robust enough to isolate highly radioactive material so that it will not threaten human health and environment for more than ten thousand years.

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30 Story of Yucca Mountain Site 1982: Nuclear Waste Policy Act Congress charges DOE with the task Two high level waste depository in the eastern and the western USA Billions collected from tax on utilities 1986: Hanford, Wa, Yucca Mtn, Ne and Deaf Smith County, Tx shortlisted as western sites 1987: Congress suddenly decides on Nevada (screw Nevada bill) Nevada to receive $20 million/year Feb 15, 2002: Pres. Bush approved Yucca Mtn as the site for high level nuclear waste respository

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33 Yucca Mountain Site Geologically stable (?) Limited fault displacement No volcanism in 10,000 years Tuff host rock, 1000 ft below the surface, 1000 ft above the water table Arid climate, no streams, low water table Low population density Federally owned land, close to Nevada test sites