The best way to avoid the environmental problems of solid waste disposal is to desist from generating wastes in the first instance. Pollution prevention programs aimed at this objective have become widespread. Recycling and reuse of materials are ways to avoid waste generation. At the residential level, recycling programs for newspapers, glass, and metal containers have been implemented. However, some municipal programs have been criticized for increasing environmental emissions of air pollutants from the fuel combustion.
The ultimate land disposal methods used for municipal solid wastes are land filling, land farming, and deep well injection. Land filling of solid wastes involves the controlled disposal of solid wastes on or in the upper layer of the Earth's mantle, which has been excavated to a depth of about 13 ft. (4 m.). When solid wastes are placed in sanitary landfills, biological, chemical, and physical processes occur. Biological decay of organic materials occurs by either aerobic or anaerobic processes, resulting in the evolution of gases or liquids. The chemical oxidation of waste materials occurs, dissolving and leaching of organic and inorganic materials by water and leachate moving through the fill also occur.
Land filling in moist climates produces large quantities of leachate that are toxic and of high organic strength and require treatment in waste-water plants. Land filling in dry climates produces localized air pollution problems. There is also movement of dissolved material by concentration gradi ents and osmosis. Initially, the organic material in the landfill undergoes aerobic decomposition due to some oxygen amount obtained in air trapped in the landfill. Within a few days, the oxygen content is exhausted and long-term decomposition occurs under aerobic conditions. The anaerobic conversion of organic compounds occurs in the transformation of high molecular weight compounds catalyzed by enzymes in soil bacteria into compounds suitable for use as a source. However, landfill sites cause soil and groundwater contamination if not properly operated. Additional environmental problems with landfill are odors, litter, scavengers, and rat infestation.
Solid wastes are those wastes from human and animal activities. In the domestic environment, the solid wastes include paper, plastics, food wastes, and ash. Improper management of solid wastes has direct adverse effects on health. Solid wastes may contain human pathogens, animal pathogens, and soil pathogens. Inadequate storage of such wastes provides a breeding ground for vermin, flies, and cockroaches, which may act as passive vectors in disease transmission. The pathogens that can cause fecal-related diseases are viruses, bacteria, protozoa, and helminths. As proper waste management involves recycling, reuse, transformation, and disposal, it is relevant to know the physical, chemical, energy, and biological properties of wastes. The physical properties that are relevant include density, moisture content, particle size distribution, field capacity, hydraulic conductivity, and shear strength. Chemical analyses required are proximate analysis, ultimate analysis, and energy content analysis. The important elements in waste energy transformation are carbon, hydrogen, oxygen, nitrogen, and sulfur.
Only 2 percent of waste is actually recycled. Solid waste recycling implies recovery of a component of waste for use in a manner different from its initial function. Recycling consists of recovering from waste the matter of which a product was made and reintroducing it into the production cycle for reproduction of the same item. Composting after decomposition by aerobic bacteria mostly readily recycles garbage, grass, and organic matter. Composting may be defined as the decomposition of moist, solid, organic matter by the use of aerobic microorganisms under controlled conditions. The end product of the decomposition is a sanitary, nuisance-free, humus-like material that can be used as soil conditioner and as partial replacement for fertilizer. In a typical operation, the municipal wastes are presorted to remove noncombustible materials and those that might have salvage value such as paper, cardboard, rags, metals, and glass. Refuse is then shredded and stacked in long piles where it degrades to humus much as it would in soil. Usually, the decomposed material contains less than 1 percent of each of the three primary fertilizer nutrients. The final step is grinding and bagging for ultimate sale as soil conditioner.
Plants die because of land pollution. Crops are affected, as they do not mature and grow well. There are three ways that people pollute the land: littering all over the land, improper garbage disposal, and dumping of chemical fluids on the land. It is not uncommon to see people throw the trash on the road while in the car. Every day, people are polluting the land. Because of pollution, people do not only affect the cleanliness of the land, but also destroy the beauty and increase avenues of contracting diseases. These negative tendencies have effects on tourism potentials of nations as tourists are turned off. Tourists won't like to take risks in an unsafe environment because of pollution. Mosquitoes live in littered empty cans. Thus, the threat of mosquito bite is imminent in a polluted land. A greater proportion of land pollution is instigated and carried out by man. Governments of nations should be alive to their responsibilities of providing a safe and secured world environment to its people.
SEE ALSO: Diseases; Nuclear Power; Pollution, Air; Pollution, Water.
BIBLIOGRAPHY. C.M.A. Ademoroti, Environmental Chemistry and Toxicology (Foludex Press, 1996); G. Kiely, Environmental Engineering (McGraw-Hill International Editions, 1998); E.S. Rubin and C.I. Davidson, Introduction to Engineering & the Environment (McGraw-Hill, 2001).
Akan Bassey Williams
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