SolidWasteManagementandDisposal固体废物管理和处置PPT课件

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1、Solid Waste Management and Disposal Outline Waste Disposal Methods Landfills, Incineration, Composting Source Reduction 源头削减 Recycling Problems and Concerns Regulating hazardous materials Hazardous vs. Toxic Setting Regulations Associated Health Risks EPAs Management Strategy Municipal Solid Waste I

2、n modern society, many products are discarded when they are broken or worn out, while others only have a temporary use.Those that have only temporary uses make up the majority of solid waste. Lack of dumping 堆放 space has become a problem for many large metropolitan 大都市 areas. Why? Population increas

3、e Convenience lifestyle Communities are increasingly concerned about waste disposal costs, and groundwater (landfill) and air quality hazards (burning). Disposable Decades In the mid 1950s a disposable 用后即弃 lifestyle was marketed as the wave of the future, and as a way to reduce household duties. Co

4、nsumerism began in earnest following WWII. Convenience was sold to prosperous post-war consumers. “Convenience” was quickly changed to necessity. Nature of the Problem Garbage = Municipal Solid Waste US produces 220 million metric tons of municipal waste per year, 2kg/p.d. US volume has doubled sinc

5、e 1960. Municipal Solid Waste Generation Rates CHN produces 108 million metric tons in 1996, 0.3kg/p.d, 0.8-2.0kg/p.d in cities. CHN volume increased 8-10% per year recently, will double in 7 years. MDCs have a higher standard of living, and thus produce more waste. Waste Generation and LifestyleWas

6、te Generation and Lifestyle Waste Disposal Methods Traditional Methods (dumping and burning) are no longer accepted. Essentially, four techniques are used:LandfillsIncineration Composting RecyclingFig. 18.7 Composition of trash (U.S. CHN) Methods of Waste Disposal Landfills Landfilling has tradition

7、ally been the primary method of waste disposal - cheap and convenient. Traditional - A simple hole in the ground to dump garbage Groundwater contamination Modern landfills have complex impermeable bottom layers to trap contaminants, and daily deposits are covered by layer of dirt.Methane gas and gro

8、undwater detection systems.Gas recovery and leachate collection and treatment systems. (biochemical process or reverse osmosis membrane) Modern landfills cost $ 1 million/ha. Modern landfills Currently, almost 57% of US municipal solid waste is deposited in landfills. 70% of CHN waste is land-filled

9、 in CHN style a valley, i.e. Hangzhou Tianziling New landfills are often resisted due to public concerns over groundwater contamination, odors, and truck traffic. Local opposition, not-in-my-backyard Unwilling of politicians, not-in-my-election-year Land scarcities, alternative way? 国 家 填 埋 堆 肥 焚 烧美

10、 国 75 5 10日 本 23 4.2 72.8德 国 45.5 4 50.5英 国 88 1 11法 国 40 22 38荷 兰 45 4 51比 利 时 62 9 29瑞 士 20 80丹 麦 18 12 70奥 地 利 59.8 24 16.3瑞 典 35 10 55澳 大 利 亚 62 11 24 外 国 城 市 生 活 垃 圾 各 种 处 理 方 式 所 占 的 比 例 （ %） Incineration Prior to 1940, incineration was common in NA and western Europe. Many incinerators were e

11、liminated because of aesthetic concerns. i.e.foul odors, gritty smoke. Currently, about 16% of US municipal solid waste is incinerated. CHN, only some large cities. Derived heat often used for electrical generation. Fig. 18.11, incinerator Incineration and electrical generation Incinerators drastica

12、lly reduce the amount of municipal solid waste - up to 90% by volume and 75% by weight. Even with modern pollution controls, small amounts of pollutants are still released into env.Air, acid gases, dioxins and furansAsh (fly ash + bottom ash), concentrated metals Cost and sitting of new incinerators

13、 major problems facing communities. incineration become effective when transportation to instant landfills. CompostingYard wasteFood wasteManure Soil additive Remove toxin away before composting Source Reduction Most fundamental method of reducing waste is to prevent it from being produced.Heavy pac

14、kaging materials to light onesSince 2 liter soft drink bottle was introduced in 1977, weight has been reduced by 35%Since 1965, aluminum cans have been reduced in weight by 35%.Making products in concentrated form, depends on consumer Recycling Currently 23% of NA waste is recycled. Recycling initia

15、tives have grown rapidly in NA during the past several years. Recycling rate, Fig.18.14 Recycling Benefits Resource Conservation Pollution Reduction Example: One Sunday edition of N.Y. times consumes 62,000 trees. Only 20% of NA paper is recycled. Example: Crushed glass reduces the energy required t

16、o manufacture new glass by 50% Recycling Concerns Plastics are recyclable, but technology differs from plastic to plastic. P. 431, close-up. Lowest recycling rate. Industry is researching new technologies. Economics are of concern. Unless demand for products keeps pace with growing supply, recycling

17、 programs will face an uncertain future. Long-term success of recycling programs is also tied to other economic incentives such as taxation and the development of and demand for products manufactured from recycled materials. Currently in the US, it is often still cheaper to use virgin material than

18、transport recycled materials. REGULATING HAZARDOUS MATERIALS Hazardous - EPA defines hazardous materials as having one or more of the following characteristics:Ignitability (Fire hazard)Corrosiveness (Corrodes material)Reactivity (Unstable)Toxicity (May release toxins) Hazardous versus Toxic Terms a

19、re not Interchangeable Toxic - Commonly refers to a narrow group of substances that cause human injury or death. Hazardous - Broader term - refers to all dangerous materials that create a human health, or environmental problem. Defining Hazardous Waste Varies from one country to another U.S. Resourc

20、e Conservation and Recovery Act (RCRA) 1976 - RCRA considers wastes toxic / hazardous if they: Cause or significantly contribute to an increase in mortality or an increase in serious irreversible, or incapacitating reversible, illness; or pose a substantial present or potential hazard to human healt

21、h or the environment when properly treated, stored, transported, disposed of, or otherwise managed. Issues Involved in Setting Regulations Identification of Hazardous &Toxic MaterialsList often limited to current offenders Setting Exposure LimitsNearly all substances are toxic in sufficient quantiti

22、esSpecies-Specific Thresholds Acute vs. Chronic ToxicityEffects of massive doses (acute) and small doses over time (chronic) differ greatly.Chronic much harder to detect SynergismMost toxicity studies done on a single compound. Persistence and Non-PersistencePersistent toxins remain in the env., ess

23、entially unchanged, for long periods - build-up leads to chronic problems.Non-Persistent toxins do not remain for a long period, and are often biodegradable, and usually responsible for acute problems. Health Risks Associated with Hazardous Wastes Each year, roughly 1,000 new chemicals are produced

24、and distributed. Main problem is chemical products and by-products of industry are often handled and disposed of improperly. Hazardous Waste Dumps: A Legacy of Abuse Before, hazardous waste was essentially unregulated. Most common disposal solution was to bury or dump the wastes without concern for

25、environmental or health risks. When sites became full or unnecessary, they were simply abandoned. Managing Hazardous Wastes Obviously, past disposal methods have failed, thus:EPA now fosters a pollution prevention hierarchy that emphasizes reducing the amount of hazardous waste produced. 1. Reduce a

26、mount of pollution at the source.2. Recycle wastes whenever possible.3. Treat wastes to reduce hazard and/or volume.4. Dispose of wastes on land or incinerate them as last resort.EPA Hierarchy: Homework: p. 435. R. Q. 2, 3, 4, 5 Maybe the best method of “disposal” is not to produce it in the first p

27、lace . Composition of trash (U.S. CHN) Landfills Landfilling has traditionally been the primary method of waste disposal - cheap and convenient. Traditional - A simple hole in the ground to dump garbage Groundwater contamination Currently, almost 57% of US municipal solid waste is deposited in landf

28、ills. 70% of CHN waste is land-filled in CHN style a valley, i.e. Hangzhou Tianziling Incinerators drastically reduce the amount of municipal solid waste - up to 90% by volume and 75% by weight. Even with modern pollution controls, small amounts of pollutants are still released into env.Air, acid ga

29、ses, dioxins and furansAsh (fly ash + bottom ash), concentrated metals Recycling Benefits Resource Conservation Pollution Reduction Example: One Sunday edition of N.Y. times consumes 62,000 trees. Only 20% of NA paper is recycled. Example: Crushed glass reduces the energy required to manufacture new glass by 50% Acute vs. Chronic ToxicityEffects of massive doses (acute) and small doses over time (chronic) differ greatly.Chronic much harder to detect SynergismMost toxicity studies done on a single compound.