环境工程原理英文课件：Chapt17 Solid Waste Management and Disposal

1、Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Enger & SmithEnvironmental ScienceA Study of InterrelationshipsThirteenth EditionChapter 17Solid Waste Management and DisposalSolid Waste Management and DisposalOutline 17.1 Kinds of Solid Waste 17.2 Munici

2、pal Solid Waste 17.3 Methods of Waste Disposal 17.1 Kinds of Solid Waste Solid waste is generally made of objects or particles that accumulate on the site where they are produced. They are typically categorized by the sector of the economy responsible for producing them.17.1 Kinds of Solid Waste Min

3、ing wastes are generated in three ways: Waste material is left on the surface. Milling tailings are dumped on the land or stored in ponds. Waste or tailings drainage often contains hazardous materials. Agricultural waste Includes waste from raising animals as well as crop and tree harvesting. 90% is

4、 used as fertilizer or other forms of soil enhancement.17.1 Kinds of Solid Waste Industrial solid waste consists of solid waste other than mining. Estimated to be between 200-600 million metric tons annually. Demolition waste Sludge Combustion ash Municipal solid waste consists of all the materials

5、people in a region no longer want. 210 million metric tons annually.17.2 Municipal Solid Waste In 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.17.2 Municip

6、al Solid Waste The Unites States produces about 210 million metric tons of municipal solid waste annually. This equates to 2 kg of trash per person per day. Per capita waste has increased 70% since 1960.17.2 Municipal Solid WasteMunicipal solid waste generation rates17.2 Municipal Solid Waste Nation

7、s with a higher standard of living tend to produce more municipal solid waste per person than less-developed countries. Large metropolitan areas have the greatest difficulty dealing with solid waste.17.2 Municipal Solid WasteWaste generation and lifestyle17.3 Methods of Waste Disposal In the past, t

8、he favored means of waste disposal was to dump solid wastes outside of city or village limits. To minimize the volume of waste, the dump was often burned. This practice is still employed in remote or sparsely populated areas in the world.17.3 Methods of Waste Disposal Five techniques are now used in

9、 waste disposal: Landfills Incineration Source reduction Composting Recycling17.3 Methods of Waste Disposal Landfills A municipal solid waste landfill is typically constructed above an impermeable clay layer, lined with an impermeable membrane. It includes mechanisms for dealing with liquid and gas

10、materials generated by the contents of the landfill. Traditionally this has been the primary method of waste disposal. Cheap and convenient Problems associated with poorly designed landfills have been recognized, and substantial efforts are made to reduce the amount of waste entering landfills.17.3

11、Methods of Waste Disposal New landfills have complex bottom layers to trap contaminant-laden leachate. Monitoring systems are necessary to detect methane gas production and groundwater contamination. In some cases, methane is collected and used to generate electricity. New landfills currently cost u

12、p to $1 million per hectare to prepare.17.3 Methods of Waste DisposalA well-designed modern landfill17.3 Methods of Waste Disposal The number of landfills is declining. Many small landfills that were not meeting regulations have been closed. Capacity has been reached. New landfills often resisted du

13、e to public concerns over groundwater contamination, odors, rodents, and truck traffic.17.3 Methods of Waste DisposalReducing the number of landfills17.3 Methods of Waste Disposal Incineration is the process of burning refuse in a controlled manner. Currently, about 15% of U.S. municipal solid waste

14、 is incinerated. Most incinerators are designed to capture heat, which is then used to make steam to produce electricity. The production of electricity partially offsets disposal costs. Most incinerators burn unprocessed municipal solid waste. This process is referred to as mass burn technology.17.3

15、 Methods of Waste Disposal Incinerators drastically reduce the amount of municipal solid waste. Up to 90% by volume and 75% by weight. Primary risks of incineration involve air quality problems and toxicity and disposal of ash. Toxic substances are more concentrated in ash.17.3 Methods of Waste Disp

16、osal Even with modern pollution controls, small amounts of pollutants are still released into environment. The cost of land and construction for new incinerators are also major concerns facing many communities.17.3 Methods of Waste Disposal U.S. EPA has not looked favorably on construction of new wa

17、ste-to-energy facilities. It has encouraged recycling and source reduction as more effective solutions to deal with solid waste.17.3 Methods of Waste DisposalDisposal methods used in various countries17.3 Methods of Waste Disposal Mulch is organic material used to protect areas where the soil is dis

18、turbed, or to control growth of unwanted vegetation. Organic materials such as large branches and bark are chopped or shredded into smaller pieces.17.3 Methods of Waste Disposal Composting is using natural decomposition to transform organic material into compost, a humus-like product with many envir

19、onmental benefits. With proper management of air and water, composting can transform large quantities of organic material into compost over a short period of time. Small-scale composting can be accomplished in the backyard, mixing green materials (grass clippings, vegetable scraps, etc.) and brown m

20、aterials (dry leaves, twigs, soiled paper towels).17.3 Methods of Waste Disposal About 3,800 composting facilities are currently in use in the United States. Most municipal programs involve one of three composting methods: Window systems Aerated piles Enclosed vessels17.3 Methods of Waste Disposal T

21、he simplest way to reduce waste is to prevent it from ever becoming waste in the first place. Source reduction is the practice of designing, manufacturing, purchasing, using and reusing materials so that the amount of waste or its toxicity is reduced.17.3 Methods of Waste Disposal Design changes Sin

22、ce the 2-liter soft drink bottle was introduced in 1977, weight has been reduced by 25%. As a result, 250 million pounds of plastic have been kept out of the waste stream. Manufacturing processes reduce waste and increase efficiency. Purchasing decisions Choose reduced packaging and plan quantities

23、accordingly.17.3 Methods of Waste Disposal Using materials to avoid waste generation Reduce use of hazardous materials. Follow label directions carefully and use the smallest amount necessary. Reusing items Delay or prevent entry of items into waste collection stream.17.3 Methods of Waste Disposal M

24、ost businesses and manufacturers have a strong economic incentive to ensure they get the most from all materials they use. Any activities that reduce the amount of waste produced, reduce the: Cost of waste disposal Amount of raw materials needed Amount of pollution generated17.3 Methods of Waste Dis

25、posal Recycling is one of the best environmental success stories of the late 20th century. In the United States, recycling (including composting) diverted about 30% of solid waste stream from landfills and incinerators in 2007. Benefits: Resource conservation Pollution reduction Energy savings Job c

26、reation Less need for landfills and incinerators17.3 Methods of Waste DisposalRecycling percentage for selected materials (2007) and recycling rates from 1960-2007.17.3 Methods of Waste Disposal Container laws provide an economic incentive to recycle. Requires a deposit on all reusable beverage cont

27、ainers. A national “bottle bill” would reduce litter, save energy and money, create jobs, and help conserve natural resources. Mandatory recycling laws provide a statutory incentive to recycle.17.3 Methods of Waste Disposal Curbside recycling provides a convenient way for people to recycle. In 1990,

28、 1,000 U.S. cities had curbside recycling programs. In 2009, 11,100 cities had curbside recycling programs. Cities with curbside recycling tend to have higher recycling rates than cities that lack such programs.17.3 Methods of Waste Disposal There are many technical and economic problems associated

29、with recycling. Plastics are recyclable, but technology differs from plastic to plastic. Milk containers tend to be high-density polyethylene (HDPE), while egg containers are polystyrene (PS), and soft-drink bottles are polyethylene terephthalate (PET).17.3 Methods of Waste DisposalIncreasing amount

30、s of plastic in trash17.3 Methods of Waste Disposal The plastics industry is researching new technologies. Economics of recycling are of concern. Unless demand for products keeps pace with growing supply, recycling programs will face an uncertain future.17.3 Methods of Waste Disposal The long-term su