Environmental engineering has been defined as the branch of engineering that is concerned with protecting the environment from the potentially deleterious effects of human activity, protecting human populations from the effects of adverse enviromnental factors, and improving enviromental quality for human health and well being.
1-1 THE ENVIRONMENT
Simply stated, the environment can be defined as one's surroundings. In terms of the envionmental engineer's involvement, however, a more specific definition is needed. To the environmental engineer, the word environment may take on global dimensions, or may, in the case of contained environments, refer to a small volume of liquid, gaseous, or solid materials within a treatment plant reactor.
The global environment consists of the atmosphere, the hydroshere, and the lithosphere in which the life-sustaining resources of the earth are contained. The atmosphere, a mixture of gases extending outward from the surface of the earth, evolved from elements of the earth that were gasified during its formation and metamorphosis. The hydrosphere consists of the oceans, the lakes and streams, and the shallow groundwater bodies that wraps the core of the earth.
The biosphere, a thin shell that encapsulates the earth, is made up of the atmosphere and lithosphere adjacent to the surface of the earth, together with the hydrosphere. It is within the biosphere that the life forms of earth, including humans, live. Life-sustaining materials in gaseous, liquid, and solid forms are cycled through the biosphere, providing sustenance to all living organisms.
Life-sustaining resources--air, food, and water--are withdrawn from the bioshere. It is also into the biosphere that waste products in gaseous, liquid, and solid forms are discharged. From the beginning of time, the biosphere has received and assimilated the wastes generated by plant and animal life. Natural systems have been ever active, dispersing smoke from forest fires, diluting animal wastes washed into streams and rivers, and converting debris of past generations of plant and animal life into soil rich enough to support future populations.
For every natual act of pollution, for every undesirable alteration in the physical, chemical, or biological characteristics of the environment, for every incident that eroded the quality of the immediate, or local, environment, there were natural actions that restored that quality. Only in recent years has it become apparent that the sustaining and assimilative capacity of the biosphere, though tremendous is not, after all, infinite. Though the system has operated for millions of years, it has begun to show signs of stress, primarily because of the impact of humans upon the environment.
1-2 THE IMPACT OF HUMANS UPON THE ENVIRONMENT
In a natural state, earth's life forms live in equilibrium with their environment. The numbers and activities of each species are governed by the resources available to them. Species interaction is common, with the waste product of one species often forming the food supply of another. Humans alone have the ability to gather resources from beyond their immediate surroundings and process those resources into different, more versatile forms. These abilities have made it possible for human population to thrive and flourish beyond natural constraints. But the natural and manufactured wastes generated and released into the biosphere by these increased numbers of human beings have upset the natural equilibrium.
Anthropogenic, or human-induced, pollutants have overloaded the system. The overloading came relatively late in the course of human interaction with the environment, perhaps because early societies were primarily concerned with meeting natural needs, needs humans share in common with most of the higher mammals. These peoples had not yet begun to be concerned with meeting the acquired needs associated with more advanced civilizations.
Satisfying Natural Needs
Early humans used natural resources to satisfy their needs for air, water, food, and shelter. These natural, unprocessed resources were readily available in the biosphere, and the residues generated by the use of such resources were generally compatible with, or readily assimilated by, the environment. Primitive humans ate plant and animal foods without even disturbing the atmosphere with the smoke from a campfire. Even when use of fire became common, the relatively small amounts of smoke generated were easily and rapidly dispersed and assimilated by the atmosphere.
Early civilizations often drank from the same rivers in which they bathed and deposited their wastes, yet the impact of such use was relatively slight, as natural cleansing mechanisms easily restored water quality. These early humans used caves and other natural shelters or else fashioned their homes from wood, dirt, or animal skins. Often nomadic, early populations left behind few items that were not readily broken down and absorbed by the atmosphere, hydrosphere, or lithosphere. And those items that were not broken down with time were so few in number and so innocuous as to present no significant solid-waste problems.
Only as early peoples began to gather together in larger, more or less stable groupings did their impact upon their local environments begin to be significant. In 61 A.D., cooking and heating fires caused air pollution problems so severe that the Roman philosopher Seneca complained of "the stink of the smoky chimneys." By the late eighteenth century, the waters of the Rhine and the Thames had become too polluted to support game fish. From the Middle Ages the areas where food and human waste were dumped harbored rats, flies, and other pests.
Satisfying Acquired Needs
But these early evidences of pollution overload were merely the prelude to greater overloads to come. With the dawn of the industrial revolution, humans were better able than ever to satisfy their age-old needs of air, water, food and shelter. Increasingly they turned their attention to other needs beyond those associated with survival. By the late nineteenth and early twentieth centuries, automobiles, appliances, and processed foods and beverages had become so popular as to seem necessities, and meeting these acquired needs had become a major thrust of modern industrial society.
Unlike the natural needs discussed earlier, acquired needs are usually met by items that must be processed or manufactured or refined, and the production, distribution, and use of such items usually results in more complex residuals, many of which are not compatible with or readily assimilated by the environment.
Take, for example, a familiar modern appliance--the toaster. The shell and the heating elements are likely to be made of steel, the handle of the lift lever of plastic. Copper wires and synthetic insulation may be used in the connecting cord, and rubber may be used on the plug. In assessing the pollutants generated by the manufacture and sale of this simple appliance, it would be necessay to include all the resources expended in the mining of the metals, the extracting and refining of the petroleum, the shipping of the various materials, then the manufacturing, shipping, and selling of the finished product. The potential impact of all of these activities upon air and water quality is significant. Furthermore, if the pollution potential involving the manufacture and use of the heavy equipment needed for the extraction and processing of the raw materials used in the various toaster components is considered, the list could go on ad nauseum. And the solid-waste disposal problems that arise when it is time to get rid of the toaster become a further factor.
As a rule, meeting the acquired needs of modern societies generates more residuals than meeting natural needs, and these residuals are likely to be less compatible with the environment and less likely to be readily assimilated into the biosphere. As societies ascend the socioeconomic ladder, the list of acquired needs, or luxuries, increases, as do the complexity of the production chain and the mass and complexity of the pollutants generated. Consequently, the impact of modern human populations upon the environment is of major concern to the environmental engineer.
1-3 THE IMPACT OF THE ENVIRONMENT UPON HUMANS
Though rivers become stagnant, skies smoke-shrouded, and dumping grounds odoriferous and unsightly, populations generally manage to ignore their impact on the environment until they begin to become aware of the ill effects that a polluted environment can have upon their own health and well-being. Though stagnant rivers, smoggy skies, and unsightly dumps were aesthetically displeasing to the citizens of overcrowded cities of earlier centuries, no attempt was made to reverse the negative impact humans had on their environment until it became evident that heavily polluted water, air and soil could exert an equally negative impact on the health, the aesthetic and cultural pleasures, and the economic opportunities of humans.
Health Concerns
Elements of the air, the water, and the land may host harmful biological and chemical agents that impact the health of humans. A wide range of communicable diseases can be spread through elements of the environment by human and animal waste products. This is most clearly evidenced by the plagues of the Middle Ages when disease spread through rats that fed on contaminated solid and human waste and disease carried by waterborne parasites and bacteria ran rampant through the population of Europe.
It has only been in the last century that the correlation between waterborne biological agents and human diseases has been proved and effective preventive measures have been taken. Through immunization and environmental control programs, the major diseases transmitted via the environment have all but been eliminated in developed countries. No country, however, is totally immune from outbreaks of environmentally transmitted disease. The transmission of viruses and protozoa has proved particularly difficult to control, and lapses in good sanitary practice have resulted in minor epidemics of other waterborne diseases.
Pollution of the atmosphere has also posed severe health problems that are of great concern to environmental engineers. People in crowded cities have likely suffered from the ill effects of air pollution for centuries, but it is only in this century that increasingly heavy pollution has caused health problems so dramatic as to be easily attributed to air pollution. Several killer smogs settled over London in the last quarter of the nineteenth century, but the true extent of the air-pollution problem in that city did not become apparent until 4000 deaths and countless illnesses were attributed to the London smog of 1952.
Though the 20 deaths caused by a smog over Donora, Pennsylvania, in 1948 raised some alarm, it was not until the New York inversion of 1963 claimed several hundred lives that this country began to take the fight against air pollution seriously. Monitoring of the sulfur dioxide, lead, and carbon monoxide levels in areas such as the smog-shrouded Los Angeles basin has revealed that the high levels of these and other contaminates pose direct and indirect threats to human health. These findings have made air-pollution control a top priority of the Environmental Protection Agency and a major concern of environmental engineers, who are now called upon to devise management programs designed to alter the pattern of air pollution begun centuries ago and continued until the present time.
Other environmentally related health problems also concern the environmental engineer. The widespread use of chemicals in agriculture and industry has introduced many new compounds into the environment. Some of these compounds have been diffused in small quantities throughout the environment, while others have been concentrated at disposal sites. Such chemicals may be spread through air, water, and soil, as well as through the food chain, and thus pose a potential threat to all humans.
The pesticide DDT was used extensively during the mid-century decades and has been instrumental in the elimination of malaria in many parts of the world. In addition, this pesticide was used extensively to control insect pests on food and fiber plants. Its beneficial use to humans was widely acclaimed, and its promoter, Paul Muller, was awarded a Nobel prize in 1958 for his contribution to public health. Subsequent research, however, has shown that DDT is a cumulative toxin that has adversely affected many nontarget species. Traces of DDT can be found in almost all living organisms throughout the world--including humans. Although the use of DDT is now banned in the United States and several other countries, the chemical is still being manufactured, primarily for use in several developing countries, particularly in tropical zones where its benefits are still considered to outweigh its liabilities.
A more recent example of chemical toxins that threaten health is the chemical dioxin. The formation of this chemical, the scientific name of which is 2,3,7,8-tetrachloro-dibenzoparadioxin, is an unintentional by-product of a manufacturing process used with some herbicides and wood-preserving compounds. It is also formed in the production of some disinfectants and industrial cleaning compunds. Dioxin is an exremely toxic substance, and its presence in excess of 1 ppb (One part per billion) in the environmental elements becomes cause for concern. (one part per billion corresponds to one drop of water in a swimming pool measuring 15 ft wide, 30 ft long, and 6 ft deep.)
Chemicals containing dioxin residuals have been used on a widespread basis during the last few decades, and the level of this chemical in the general environment is not currently known. The discovery of dioxon residuals in waste-disposal sites and in soils that were contaminated through application of the parent material has caused great concern and has resulted in expensive cleaning efforts. The creation of a "superfund" in the Environmental Protection Agency, initially funded at several billion dollars, is but a start in the efforts to mitigate the hazards of chemicals in the environment.
Other Concerns
Clean air and water are an aesthetic delight, yet city dwellers have all but forgotten the smell of clean air, and clear, sparkling lakes, rivers, and streams are becoming increasingly rare. Littered streets and highways offend, rather than delight, and unfenced junkyards and uncontrolled dumps give further evidence of the aesthetically displeasing effect of improper solid-waste disposal techniques.
Our cultural as well as our aesthetic heritage is also being lost to pollution. The Parthenon in Athens, the Statue of Libery in New York harbor, the statues and frescoes in Venice have withstood the onslaught of the elements for centuries, yet are in increasing danger of being destroyed by the constituents of a polluted atmosphere.
And pollution poses economic threats to human populations. Lake Erie once supported a thriving fishing industry and all the attendant processing and shipping facilities associated with that industry, yet the economic potential of the lake was nearly lost before serious cleanup efforts were begun. The silting in of rivers, harbors, and reservoirs due to uncontrolled erosion, often exacerbated by human activities, threatens to strengthen some industries at the expense of others.
Environmental engineers are committed to protecting humans from the threats a polluted environment pose to human health, aesthetic and cultural enjoyment, and ecomonic well-being.
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