Water pollution

Water pollution is a large set of adverse effects upon water bodies (lakes, rivers, oceans, groundwater) caused by human activities. Although natural phenomena such as volcanoes, storms, earthquakes etc. also cause major changes in water quality and the ecological status of water, these are not deemed to be pollution. Water pollution has many causes and characteristics. Humans and other farmed organisms produce bodily wastes which enter rivers, lakes, oceans and other surface waters. These wastes increase the solids suspended in the water (turbidity), they can increase the concentration of bacteria and viruses leading to potential health impacts. Increases in nutrient loading may lead to eutrophication. Organic wastes such as sewage and farm waste impose high oxygen demands on the receiving water leading to oxygen depletion with potentially severe impacts on the whole eco-system. Industries discharge a variety of pollutants in their wastewater including heavy metals, organic toxins, oils, nutrients, and solids. Discharges can also have thermal effects, especially those form power stations, and these too reduce the available oxygen. Silt-bearing runoff from many activities including construction sites, forestry and farms can inhibit the penetration of sunlight through the water column restricting photosynthesis and causing blanketing of the lake or river bed which in turns damages the ecology.

Pollutants in water include of a wide spectrum of chemicals, pathogens, and physical chemistry or sensory changes. Many of the chemical substances are toxic or even carcinogenic. Pathogens can obviously induce disease in either human or animal hosts. Alteration of water's physical chemistry include acidity, conductivity, temperature, and excessive nutrient loading (eutrophication). Even many of the municipal water supplies in developed countries can present health risks. In the U.S.in 1972 stringent federal laws were enacted setting specific discharge limitations.

Water pollution is a serious problem in the global context. It has been suggested that it is the leading worldwide cause of death and disease, and that it accounts for the deaths of more than 14,000 people daily.

Sources of water pollution

Principal sources of water pollution are:

industrial discharge of chemical wastes and byproducts
discharge of poorly-treated or untreated sewage
surface runoff containing pesticides
slash and burn farming practice, which is often an element within shifting cultivation agricultural systems
surface runoff containing spilled petroleum products
surface runoff from construction sites, farms, or paved and other impervious surfaces e.g. silt
discharge of contaminated and/or heated water used for industrial processes
acid rain caused by industrial discharge of sulfur dioxide (by burning high-sulfur fossil fuels)
excess nutrients added by runoff containing detergents or fertilizers
underground storage tank leakage, leading to soil contamination, thence aquifer contamination.

Contaminants

Contaminants may include organic and inorganic substances.

Some organic water pollutants are:

insecticides and herbicides, a huge range of organohalide and other chemicals
bacteria, often is from sewage or livestock operations;
food processing waste, including pathogens
tree and brush debris from logging operations
VOCs (Volatile Organic Compounds, industrial solvents) from improper storage

Some inorganic water pollutants include:

heavy metals including acid mine drainage
acidity caused by industrial discharges (especially sulfur dioxide from power plants)
chemical waste as industrial byproducts
fertilizers, in runoff from agriculture including nitrates and phosphates
silt in surface runoff from construction sites, logging, slash and burn practices or land clearing

Transport and chemical reactions of water pollutants

Most water pollutants are eventually carried by the rivers into the oceans. In some areas of the world the influence can be traced hundred miles from the mouth by studies using hydrology transport models. Advanced computer models such as SWMM or the DSSAM Model have been used in many locations worldwide to examine the fate of pollutants in aquatic systems. Indicator filter feeding species such as copepods have also been used to study pollutant fates in the New York Bight, for example. The highest toxin loads are not directly at the mouth of the Hudson River, but 100 kilometers south, since several days are required for incorporation into planktonic tissue. The Hudson discharge flows south along the coast due to the coriolis force. Further south then are areas of oxygen depletion, caused by chemicals using up oxygen and by algae blooms, caused by excess nutrients from algal cell death and decomposotion. Fish and shellfish kills have been reported, because toxins climb the foodchain afer small fish consume copepods, then large fish eat smaller fish, etc. Each step up the food chain concentrates certain toxins like heavy metals and DDT by approximately a factor of ten.

For several years ocean researcher Charles Moore has been investigating a concentration of floating plastic debris in the Pacific Ocean. His study indicates that ocean currents have added to the mass until it is now about the size of Texas. Many of these long-lasting pieces wind up in the stomachs of marine birds and animals.^*

Many chemicals undergo reactive decay or change especially over long periods of time in groundwater reservoirs. A noteworthy class of such chemicals are the chlorinated hydrocarbons such as trichloroethylene (used in industrial metal degreasing) and tetrachloroethylene used in the dry cleaning industry. Both of these chemicals, which are carcinogens themselves, undergo partial decomposition reactions leading to new hazardous chemicals.

Groundwater pollution is much more difficult to abate than surface pollution because groundwater can move great distances through unseen aquifers. Non-porous aquifers such as clays partially purify water of bacteria by simple filtration (adsorption and absorption), dilution, and, in some cases, chemical reactions and biological activity: however, in some cases, the pollutants merely transform to soil contaminants. Groundwater that moves through cracks and caverns is not filtered and can be transported as easily as surface water. In fact this can be aggravated by the human tendency to use natural sinkholes as dumps in areas of Karst topography.

There are a variety of secondary effects stemming not from the original pollutant, but a derivative condition. Some of these secondary impacts are:

Silt bearing surface runoff from can inhibit the penetration of sunlight through the water column, hampering Photosynthesis in aquatic plants.
Thermal pollution can induce fish kills and invasion by new thermophyllic species

Regulatory framework

In the UK there are common law rights to protect the passage of water across land unfettered in either quality of quantity. Criminal laws dating back to the 16th century excercised some control over water pollution but it was not until the River (Prevention of pollution )Acts 1951 - 1961 were enacted that any systematic control over water pollutuion was established. These laws were strengthened and extended in the Control of Pollution Act 1984 which has since been updated and modified by a series of further acts.

Concern over water pollution in the USA resulted in the enactment of state anti-pollution laws in the latter half of the 19th century, and federal legislation enacted in 1899. The Refuse Act of the federal Rivers and Harbors Act of 1899 prohibits the disposal of any refuse matter from into either the nation's navigable rivers, lakes, streams, and other navigable bodies of water, or any tributary to such waters, unless one has first obtained a permit.

Growing public awareness and concern for controlling water pollution led to enactment of the Federal Water Pollution Control Act Amendments of 1972. As amended in 1977, this law became commonly known as the Clean Water Act. The Act established the basic mechanisms for regulating contaminant discharge. It established the authority for EPA to implement wastewater standards for industry. The Clean Water Act also continued requirements to set water quality standards for all contaminants in surface waters. Further amplification of the Act continued including the enactment of the Great Lakes Legacy Act of 2002 (Public Law 107-303, November 27, 2002).

References

Bibliography

Abel, P.D. (1996). Water Pollution Biology, Taylor & Francis. ISBN 0-7484-0661-1.

Beychok, Milton R. (1967). Aqueous Wastes From Petroleum and Petrochemical Plants, 1st Edition, John Wiley & Sons. LCCN 67-19834.

Liu, David H.F., Liptak, Bela G. and Bouis, Paul A. (2000). Groundwater and Surface Water Pollution, CRC Press. ISBN 1-56670-511-8.

Tchobanoglous, G, Burton, F L, & Stensel, H D (2003). Wastewater Engineering (Treatment Disposal Reuse) / Metcalf & Eddy, Inc, 4th Edition, McGraw-Hill Book Company. ISBN 0070418780.

Great Lakes Legacy Act of 2002, Public Law 107-303, November 27, 2002

U.S. Clean Water Act of 1972

External links

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