490. UNIT FOUR ENVIRONMENTAL HEALTH AND SAFETY CAKDRIDCE·50 MERVILLE FIGURE 15.2 Urbanization has led to overcrowding and pollution While it is unrealistic to believe humans can have a pollution-free environ- ment,it is possible to work toward minimizing the level of pollution. As the domi- nant species on this planet, our very survival depends upon our recognition of the deleterious effects our activities have on the rest of the biosphere and our taking responsibility for minimizing these effects. If the environment is to remain rela tively stable, the frequency and severity of environmental hazards stemming from human activities must be reduced Table 15.1 Reusable versus Throwaway Consumer Goods Reusable goods Throwaway Goods Milk bottles Cardboard cartons and plastic jugs Returnable soft drink bottles Aluminum cans and plastic bottles Garbage cans Trash bags Lunch boxes Paper bags Cloth napkins Paper napkins Refillable pens Disposable pens Handkerchiefs Facial tissues Cloth towels or rags Paper towels Ceramic or plastic dishes Paper plates
CHAPTER 15 ENVIRONMENTAL CONCERNS: WASTES AND POLUTON 491 TYPES OF WASTES AND POLLUTION The types of wastes and pollution discussed below include solid wastes, hazardous wastes,air pollution, water pollution, radiation, and noise pollution. While some types of wastes may merely lower the aesthetic value of the environment, others constitute either an immediate or longterm threat to human health and well being Solid Waste Household trash, grass clippings, tree trimmings, manure, excess stone generated from mining, and steel scraps from automobile plants are all examples of solid waste.Today we are generating solid wastes in record quantities. In the last 40 olid fom years, the daily solid waste production per person in the United States jumped agriculture, and from just over 2.5 pounds to almost 4.5 pounds. Many communities have used up businesses all available space to bury their solid waste. If they cannot find a neighboring com- munity to accept their waste they must ship it elsewhere(see Figure 15.3) Sources of Solid waste Most solid waste can be traced to five major sources: agriculture, mining, industry, municipalities(domestic sources) and utilities. By far, agriculture generates the greatest volume of solid waste, more than 50% of the total (see Figure 15.4). Examples of agricultural wastes include crop residues, manures, and other vegeta tion trimmings. Most solid waste generated by farming will decompose, enriching FIGURE 15.3 Solid waste is becoming such a problem in some areas that it is shipped elsewhere
492. UNIT FOUR ENVIRONMENTAL HEALTH AND SAFETY the soil, or can be fed to animals or otherwise used as energy Farms have long been known for recycling their own nonhuman solid waste Unlike agricultural waste, mining waste does not decompose in any reasonable period of time nor can it be reused in any other manner. As the extraction of the earth's natural resources intensifies, mining wastes will constitute even greater problems. Mining waste makes 12% up about 39% of the total amount of solid waste gener 3.1% ated by humans The solid waste resulting from industrial production 64% is quite varied and constitutes 6.4% of the total Examples include paper, wood chips, and highly com lex chemicals. Certain industrial waste products are especially hazardous because of their toxicity, corrosive ness, or flammability. Agriculture Municipal Household or municipal waste makes up just over Industrial 3% of all solid waste generated each year. It includes wastes generated by individual households, busi nesses FIGURE 15. 4 and institutions located within municipalities. This Sources of solid waste waste is known as municipal waste. While it makes up Source: McKinney, M. L, and R. M. Schoch(1998) nly 3. 1% of unicipal solid waste Environmental Science: Systems and Solutions. Web receives considerable attention because it is visible mal- enhanced edition. Sudbury, MA: Jones and Bartlett dorous, and considered a threat to human health if not sposed of properly The heterogeneous makeup of municipal solid waste precludes efficient dis- osal. There are seven major categories: paper, yard waste, rubber, textiles and wood,metal, glass, plastic, and food wastes(see Figure 15.5). Forty years ago food businesss. und wastes were the primary component in municipal solid waste, but garbage dis- unicipolitis posals in homes and the preprocessing of foods have reduced that greatly. Today, institutions located PGpm①3% the total. mud由书pk吗me the burning of coal. Solid Waste Management lid waste Strictly defined, solid waste management is the collection, transportation, and disposal of solid waste. a broader definition of solid waste management also includes source-reduction efforts that limit the production of solid waste in the disposal of solid waste first place. Though the preponderance of solid waste is created by agriculture and mining, the following discussion of solid waste management is aimed primarily at municipal and industrial wastes, which create greater problems in the environ mental system Collection The handling of municipal solid waste can be divided into two steps: collection and disposal. Approximately 80% of the money spent on waste management is spent on the collection process. Faced with ever-increasing amounts of waste
CHAPTER 15 ENVIRONMENTAL CONCERNS: WASTES AND POUUTION. 493 37.5% 179% 24% 28% 63% 6.7% 63%67% FIGURE 15.5 Paper and paperboard Ferrous metals Types and percentages of municipal Yard wastes Plastics and leather McKinney, M. L, and r.M. Glass Food wastes Miscellaneous edition. Sudbury, MA: Jones greater efficiency is needed in collecting the wastes so that more money can be pent on environmentally sound disposal. Traditionally, municipal wastes have been collected at the curb or alley by crews of three people and a large truck However, experience has shown that crew size, truck size, and special-feature trucks-like those that can be operated by a single person or those with different storage compartments for separating the trash-can improve efficiency and reduce sanitary landfills waste disposal site cost(see Figure 15.6). Moreover, the collecting and transporting of trash through on land suited for this pipelines hydraulically and/or pneumatically(the method used at Disney World) purpose and upon can make collection even more efficient which waste is spread Currently most municipalities dispose of their wastes in sanitary landfills, sites layer of day or plasic judged suitable for inground disposal of solid waste. However, many of these foam each day municipal landfills are filling up, and the availability of land suitable for new landfill sites near cities is quickly disappearing. Disposal of municipal solid waste on unsuitable land can result in the contamination of groundwater (water found in the ground), which may be the community's only source of drinking water. To meet integrated waste the need for better management of solid waste, many communities have adopted app an integrated waste management approach. This approach combines the fol- lowing four methods in a way best suited to local needs and capabilities: (1) sani. dispin ofsold tary landfills, (2)incineration, (3)recycling, and (4)source reduction. 2 sanitary lo incineratiOn Sanitary landfill Prior to the mid-1970s much of the solid waste in the United States was simply source reduction placed in a hole in the ground with little thought given to the underlying soil type
49·UN盯 FOUR ENVIRONMENTAL HEALTH AND SAFETY FIGURE 15.6 Household waste picked up at the curbside with a segregated container, recycling truck location, and depth of groundwater and little concern for neighbors. These open dumps, while cheap and convenient, were unsanitary because they supported open pits in whic large populations of rodents, flies, and vermin. Such dumps also produced leachates, liquids created when water mixes with wastes and removes soluble constituents from them by percolation, which too often found their way into underlying groundwater Dumps were a health hazard and reduced the value of adjacent property because of their obnoxious odors, their unsightliness, and their generally unsanitary conditions. ater mixes w The passage of the Resource Conservation and Recovery Act of 1976 soluble constituents(RCRA, pronounced Rick-Rah) provided legislation that phased out open dumps from them by and required that the disposal of solid waste be done in sanitary landfills. Unlike dumps, sanitary landfills are supposed to be located at sites that can geographically and geologically support them, sites with natural clay soils. If clay soil cannot be found, a clay lining must be constructed to prevent leachates from reaching groundwater. Sanitary landfills are not to be located over sand or gravel deposits ation nd Recovery Act of that would allow leachates to reach ground water. Second, in sanitary landfills all refuse is spread and compacted in thin layers by bulldozers. Once the compacted the federal low that sets forth guidelines layers are about eight to ten feet thick, they are covered with about six inches of soil, compacted again, and readied for another ayer of refuse. At the end of each andling nd disposa day, unlike an open dump, refuse is covered with a layer of soil. This process con of hazardous wos tinues until the landfill is full, at which time a final layer of soil about two feet thick is placed on the top. When this process is strictly followed, sanitary landfills pro-