Solid Waste Management and Disposal固体废物管理和处置.ppt

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 increa

3、se 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. C

4、onsumerism 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 sin

5、ce 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 Lifestyle,W

6、aste Generation and Lifestyle,Waste Disposal Methods,Traditional Methods (dumping and burning) are no longer accepted. Essentially, four techniques are used: Landfills Incineration Composting Recycling Fig. 18.7,Composition of trash (U.S. CHN),Methods of Waste Disposal,Landfills Landfilling has trad

7、itionally 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 a

8、nd groundwater 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

9、-filled 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?,外国城市生活垃圾各

10、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 eliminated 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

11、 used for electrical generation. Fig. 18.11, incinerator,Incineration and electrical generation,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. A

12、ir, acid gases, dioxins and furans Ash (fly ash + bottom ash), concentrated metals,Cost and sitting of new incinerators major problems facing communities. incineration become effective when transportation to instant landfills.,Composting Yard waste Food waste Manure Soil additive Remove toxin away b

13、efore composting,Source Reduction,Most fundamental method of reducing waste is to prevent it from being produced. Heavy packaging materials to light ones Since 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

14、%. Making products in concentrated form, depends on consumer,Recycling,Currently 23% of NA waste is recycled. Recycling initiatives have grown rapidly in NA during the past several years. Recycling rate, Fig.18.14,Recycling Benefits,Resource Conservation Pollution Reduction Example: One Sunday editi

15、on 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%,Recycling Concerns,Plastics are recyclable, but technology differs from plastic to plastic. P. 431, close-up. Lowest recycling rate. Industry i

16、s researching new technologies. Economics are of concern. Unless demand for products keeps pace with growing supply, recycling 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

17、for products manufactured from recycled materials. Currently in the US, it is often still cheaper to use virgin material than transport recycled materials.,REGULATING HAZARDOUS MATERIALS,Hazardous - EPA defines hazardous materials as having one or more of the following characteristics: Ignitability

18、(Fire hazard) Corrosiveness (Corrodes material) Reactivity (Unstable) Toxicity (May release toxins),Hazardous versus Toxic Terms are not Interchangeable,Toxic - Commonly refers to a narrow group of substances that cause human injury or death. Hazardous - Broader term - refers to all dangerous materi

19、als that create a human health, or environmental problem.,Defining Hazardous Waste,Varies from one country to another U.S. Resource Conservation and Recovery Act (RCRA) 1976 -,RCRA considers wastes toxic / hazardous if they:,Cause or significantly contribute to an increase in mortality or an increas

20、e in serious irreversible, or incapacitating reversible, illness; or pose a substantial present or potential hazard to human health or the environment when properly treated, stored, transported, disposed of, or otherwise managed.,Issues Involved in Setting Regulations,Identification of Hazardous &To

21、xic Materials List often limited to current offenders Setting Exposure Limits Nearly all substances are toxic in sufficient quantities Species-Specific Thresholds,Acute vs. Chronic Toxicity Effects of massive doses (acute) and small doses over time (chronic) differ greatly. Chronic much harder to de

22、tect Synergism Most toxicity studies done on a single compound.,Persistence and Non-Persistence Persistent toxins remain in the env., essentially 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 and distributed. Main problem is chemical products and by-products of industry are often handled and disposed of improperly.,Hazardous Waste Dumps: