When the bottle is exposed to sunlight and small inoculums of living matter including green plant is introduced into the bottle, various life activities such as assimilation and breakdown of organic matter can start and may give us an idea of how biogeochemical cycles control the composition of the aquatic and atmospheric environments. The solar radiation creates a flow of energy through the system.
The earth is an ‘entropy pump’ which extracts energy from the stream of radiation to power and drive the cycles of water, nutrients and other elements as also the cycles of life through different trophic levels. Laws of thermodynamics dictate that spontaneously occurring natural processes be accompanied by an increase of entropy or randomness.
The change from an initial transitory state to a final stationary phase seems to involve a decrease in entropy and it may be inferred that a stationary phase is fairly stable against external disturbances since a low entropy system is unable to spontaneously move to a high entropy form (the natural tendency lies in the opposite direction).
For instance, within the closed bottle, the stationary phase is approached with considerable decrease in natural energy flow. This results in succession of ecosystems with the ecosystem organization increasing progressively.
Generally, natural ecosystems evolve from unstable to stable conditions. Such evolution involves decline in net productivity as well as entropy but increase in species diversity.
Within the biosphere, any individual plant or animal relates to its total environment and is shaped by it. The individual must engage in an effective interplay not only with other individuals of its own species but also with other members of his community, including microbes, plants, animals and man. An individual has also to respond to the ever-changing physical forces of the environment.
Out of the various components that affect the biosphere, the two more important ones, from the viewpoint of mankind, are: (a) resource production, and (b) waste disposal. A proper balance between these two factors is necessary for a healthy biosphere.
Frequently, certain resources are created with a useful purpose or some economic advantage for the human being, but on actual use it is found that some such resources, as e.g., synthetic detergents, persistent pesticides, medicinal drugs, non-biodegradable substances, etc., have highly serious side-effects. Some of these wastes cannot be degraded or processed by nature within a reasonable period of time and such wastes begin to accumulate and pollute the environment.
If such wastes could be converted into usable form, it would not only relieve of pollution but also improve, or at least maintain, environmental quality and the production of future resources. Reversal of environmental deterioration must form one of the major goals of our society.
Billions of tons of municipal waste are generated each year of which about 60-70% (paper, yard and food wastes) are easily biodegradable and therefore especially amenable to biological treatment. About 12-16 percent (rubber, leather and plastic waste) are potentially biodegradable.
Currently, only a small fraction of the potential waste is treated by utilizing biotechnology. Micro-organisms are responsible for much of the natural degradation that slowly remediates contaminants released into the environment.
The specific mechanisms involved include biodegradation (often enzymatic), accumulation, biologically induced precipitation, bioenhanced filtration, formation of biological barriers and the bioregeneration of granular activated carbon. Genetic modification of the micro-organisms involved can sometime further improves the above methods. Currently, micro-organisms are being “improved” through selective breeding. The key to biotechnology’s use in environmental management is the micro-organisms used. Very often, naturally- occurring microbes are used. Land farming especially oilfield waste land farming represents a large market for environmental remediation via biotechnology.
The oilfield has long relied on “land farming” of the hydrocarbon-rich contaminants produced during petroleum recovery. During land farming, the wastes are buried and become exposed to the oil-degrading microbes present in soil.
Recently, it has become possible to biodegrade or treats a wider variety of hazardous waste, such as oils, fuels, solvents, pesticides and some heavy metals. Advanced microbial treatment involves techniques involving bacteria, fungi, or other micro-organisms. Microbial action can also convert wastes into energy through biodegradation and fermentation.
It is also possible to mine old municipal waste dumps for methane and municipal waste may possibly be converted directly into fuel without air-polluting incineration. Composing is another low-tech microbial waste treatment. Both sledges and biodegradable solid wastes can be composed. Composting yard wastes is an especially attractive option since it reduces air pollution and does not use municipal landfill space.
Three general types of thermal processes are now available for recovering energy from solid wastes; these are mass burning, cofiring, and pyrolysis. Mass burners (water wall incinerators) produce steam through direct combustion of solid wastes.
Cofiring produces steam, and/or electricity through combustion of processed solid waste and some fossil fuel in a fossil fuel fired boiler. Pyrolysis units employ destructive distillation to convert waste material into a gaseous, liquid, or solid fuel product. Pyrolysis often results in the concentration of traces of organics and minerals into gaseous, liquid or solid products. Organic wastes can be used to produce biogas.
The sanitary landfill is the primary and the most economical mode of disposal of solid waste. However, landfill operations release two primary sources of pollution, viz., liquid leachates, and gaseous emissions from the decomposition of organic materials.
In the present conditions, what is desired is not so much the ability of human beings to conquer Nature but rather a balanced and harmonious collaboration with its forces. The ultimate goal of conservation should be to manage the environment in such a way that it can contribute to man’s happiness, health and enjoyment. Man’s interaction with his environment implies continuous and synchronous changes both in man and the environment and it is greatly to be desired that such alterations should always remain within the limits dictated by the laws of Nature (Dubos, 1969).
The biosphere depends for its existence on (a) the atmosphere, which includes air, (b) the hydrosphere, including rivers, lakes and oceans; and (c) the lithosphere, from which the soil has been derived. These three spheres are intimately interwoven and it is this whole complex which is necessary for the well-being of life on the biosphere.
If any one of the three spheres (air, water and soil) is abused, insulted or destroyed, the resulting damage is likely to be transmitted to the other two elements also. Cleaning or improving one element, followed by dumping the refuse into another cannot solve our problems since this only means shifting of the problem from one element to another.
Thus, for instance, one may arrange to cleanse a natural water body of its impurities, through a sewage treatment system; the latter burns these impurities which are released into the air as noxious gases. We have cleansed the water but polluted the air. In the same way, nothing is to be gained by cleansing the land of organic wastes which are then discharged into rivers and lakes since in this way we are only transferring the pollution from land to water.
Pollutants are not inherently bad. In most rases they are valuable commodities in the wrong places. Inefficient technology may be the basic cause of man-made pollution; another cause being our failure to develop closed-loop systems. It is easier, but not more economical, to discard or throw away wastes than to recycle them. We often worry that we are running out of resources. In fact, the chemicals are not gone; they are simply misplaced. They are scattered in the environment in such a way that we cannot use them.
The question of learning and discovering more about the natural ecosystems of the Planet Earth and how these are affected by man’s activities and misdeeds, is now of primary concern to most developed and at least some developing countries. However, one thing that is already definitely known is that there are limits to the burdens that the components of the natural system can tolerate.
In recent years excessive and intolerable pollution loads have been reflected in such danger signals as depletion of oxygen in inland seas, emergence of pesticide-resistant strains of crop pests, conversion of tropical forest soils to laterite-soils and excessive CO2 content in the air, etc.
Some pollutants also exhibit interactive or synergistic patterns. Biological interactions of sulphate and ozone on animals and of SO2 and ozone on plants have received much attention during the last decade.
In recent decades human activities have led to great increases in emissions of pollutants to the atmosphere and their subsequent deposition from the atmosphere mainly through expanding use of fossil fuels, fertilizers, agro- chemicals, and disposal of industrial, urban, and agricultural wastes.
Atmospheric pollutants are imported, transported, exported, accumulated, and even altered before they are deposited. Upon deposition, pollutants may produce beneficial, detrimental, or both types of effects which may be immediate, acute and apparent and they may be delayed, chronic or accumulative and subtle.
Apart from use of individual devices for pollution control, a recent trend is to use combinations of control devices. An example is the use of scrubbers for SO2 control in combination with other devices for particulate control, such as an electrostatic precipitator. If the particulate control device treats the flue gas before the scrubber, the scrubber will remain relatively free of fly-ash thus permitting better reuse of scrubber products. Combination devices are being increasingly employed to control pollution arising from coal combustion and power plants, etc.
Mining activities constitute one of the largest producers of solid waste. Extraction of fuel being a destructive process, environmental degradation is an inevitable result of such mining. The various environmental pollution problems arising from mining include solid wastes, water pollution, air pollution, noise, and aesthetics.
The handling and disposal of the solid waste is the principal cause for disturbed lands. During mining and beneficiation, environmental problems can arise from the runoff from the disturbed area, water in the pit area, noise and dust from blasting, extraction, haulage, storage, and grinding, etc.
Acid mine drainage is a unique source of pollutant because acid generation and discharges continue even after mining has ceased. Coal mining operation releases some acid arising from the exposure of iron sulphide minerals found in the coal.
By way of control, certain steps may be followed during the mining operation to prevent the acid from being formed, or alternatively, several techniques are now available to treat the acid produced from a mine. One very effective method of preventing acid formation is to install an oxygen barrier, such as suitable vegetation. Vegetation controls erosion and, after its death, uses up oxygen through the decomposition process.
This further facilitates the effectiveness of the barrier. Other effective barriers are soil and water. In place neutralization (by lime) is the most important treatment process used by industry to control acid mine drainage. Such neutralization removes the acidity, increases the pH, removes heavy metals, and oxidizes ferrous to ferric iron.
Some serious shortcomings of neutralization process include the following:
(1) hardness is not decreased;
(2) sulphate content is not decreased;
(3) iron content is not decreased significantly;
(4) waste sludge is produced.
Modern fossil-fueled thermal power plants produce all kinds of pollution, viz., air, water, and solid waste. Adverse environmental impacts, such as damage or destruction of benthic, planktonic, and nektonic organisms, can often be related to intake of cooling water and discharge of heated water into surface waters.
Almost all of man’s activities produce wastes. Many wastes can be recycled or reduced at source but some wastes and their residues are inevitable and have to be placed in landfill sites. Up to 80- 90 per cent of our refuse has generally been disposed off on the land which is, in many cases, an acceptable receptor for many residues provided that they are properly disposed off and monitored.
Of the many types of wastes that end up on the land, many are quite innocuous. Others can cause problems. Hazardous wastes come from industries, agriculture, and other sources. In general, much of a nation’s prosperity and economic well-being stems from activities that have produced hazardous wastes. Their proper disposal often presents tricky problems and needs careful consideration. Some big chemical companies are now installing huge incinerators to handle the wastes produced by them.
In many countries, subsurface emplacement of fluid wastes has been practised since long. Subsurface injection of waste materials should be based on due considerations of the geology of the disposal site, the nature of the waste and the design of operating procedures used. In the right conditions, subsurface injection can be more protective of public health than certain other (alternative) methods of waste disposal. A properly designed injection well emplaces fluids underneath any underground source of drinking water. Injection wells that are poorly engineered, constructed or maintained can cause contamination of groundwater.