Water pollution is a large set of adverse effects upon water bodies such as lakes, rivers, oceans, and groundwater caused by human activities.

Although natural phenomena such as volcanoes, algae blooms, storms, and earthquakes also cause major changes in water quality and the ecological status of water, these are not deemed to be pollution. Water is only called polluted when it is not able to be used for what one wants it to be used for. Water pollution has many causes and characteristics. Increases in nutrient loading may lead to eutrophication. Organic wastes such as sewage 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, resin pellets, organic toxins, oils, nutrients, and solids. Discharges can also have thermal effects, especially those from power stations, and these too reduce the available oxygen. Silt-bearing runoff from many activities including construction sites, deforestation and agriculture can inhibit the penetration of sunlight through the water column, restricting photosynthesis and causing blanketing of the lake or river bed, in turn damaging ecological systems.

Pollutants in water include a wide spectrum of chemicals, pathogens, and physical chemistry or sensory changes. Many of the chemical substances are toxic. Pathogens can produce waterborne diseases in either human or animal hosts. Alteration of water's physical chemistry include acidity, conductivity, temperature, and eutrophication. Eutrophication is the fertilisation of surface water by nutrients that were previously scarce. Even many of the municipal water supplies in developed countries can present health risks. Water pollution is a major problem in the global context. It has been suggested that it is the leading worldwide cause of deaths and diseases, [1][2] and that it accounts for the deaths of more than 14,000 people daily.[2]

Sources of water pollutionSome of the principal sources of water pollution are:

Geology of aquifers from which groundwater is abstracted Industrial discharge of chemical wastes and byproducts Discharge of poorly-treated or untreated sewage Surface runoff containing pesticides or fertilizers 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 sulphur dioxide (by burning high-

sulphur fossil fuels) Excess nutrients are added (eutrophication) by runoff containing detergents or

fertilizers

Underground storage tank leakage, leading to soil contamination, and hence aquifer contamination

Inappropriate disposal of various solid wastes and, on a localized scale, littering Oil spills

ContaminantsContaminants 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), such as industrial solvents, from improper storage

Petroleum Hydrocarbons including fuels (gasoline, diesel, jet fuels, and fuel oils) and lubricants (motor oil) from oil field operations, refineries, pipelines, retail service station's underground storage tanks, and transfer operations. Note: VOCs include gasoline-range hydrocarbons.

Some inorganic water pollutants include:

Heavy metals including acid mine drainage

Acidity caused by industrial discharges (especially sulfur dioxide from power plants)

Pre-production industrial raw resin pellets, an industrial pollutant

Chemical waste as industrial by products

Fertilizers, in runoff from agriculture including nitrates and phosphates

Silt in surface runoff from construction sites, logging, slash and burn practices or land clearing sites

Transport and chemical reactions of water pollutantsMost 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 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 decomposition. Fish and shellfish kills have been reported, because toxins climb the foodchain after small fish consume copepods, then large fish eat smaller fish, etc. Each successive step up the food chain causes a stepwise concentration of pollutants such as heavy metals (e.g. mercury) and persistent organic pollutants such as DDT. This is known as biomagnification which is occasionally used interchangeably with bioaccumulation.

The big gyres in the oceans trap floating plastic debris. The North Pacific Gyre for example has collected the so-called Great Pacific Garbage Patch that is now estimated at two times the size of Texas. Many of these long-lasting pieces wind up in the stomachs of marine birds and animals. This results in obstruction of digestive pathways which leads to reduced appetite or even starvation.

Many chemicals undergo reactive decay or chemially 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 electronics manufacturing) and tetrachloroethylene used in the dry cleaning industry (note latest advances in liquid carbon dioxide in dry cleaning that avoids all use of chemicals). Both of these chemicals, which are carcinogens themselves, undergo partial decomposition reactions, leading to new hazardous chemicals (including dichloroethylene and vinyl chloride).

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

Sources of Water Pollution

What are the sources of water pollution?What are the effects of water pollution?

What are the ways we can take to decrease those problem?

a)What are the sources of water pollution?

There are many causes for water pollution but two general categories exist: direct and indirect contaminant sources.

Direct sources include effluent outfalls from factories, refineries, waste treatment plants etc.. that emit fluids of varying quality directly into urban water supplies. In the United States and other countries, these practices are regulated, although this doesn't mean that pollutants can't be found in these waters.

Indirect sources include contaminants that enter the water supply from soils/groundwater systems and from the atmosphere via rain water. Soils and groundwaters contain the residue of human agricultural practices (fertilizers, pesticides, etc..) and improperly disposed of industrial wastes. Atmospheric contaminants are also derived from human practices (such as gaseous emissions from automobiles, factories and even bakeries).

Source: Our Planet, Vol 8, No.3, 1996.

Contaminants can be broadly classified into organic, inorganic, radioactive and acid/base. Examples from each class and their potential sources are too numerous to discuss here.

b)What are the effects of water pollution?

The effects of water pollution are varied. They include poisonous drinking water, poisionous food animals (due to these organisms having bioaccumulated toxins from the environment over their life spans), unbalanced river and lake ecosystems that can no longer support full biological diversity, deforestation from acid rain, and many other effects. These effects are, of course, specific to the various contaminants.

c)What are the ways we can take to decrease those problem?

Science provides many practical solutions to minimizing the present level at which pollutants are introduced into the environment and for remediating (cleaning up) past problems. All of these solutions come with some cost (both societal and monetary). In our everyday lives, a great deal can be done to minimize pollution if we take care to recycle materials whose production creates pollution and if we act responsibly with household chemicals and their disposal. Additionally, there are choices we make each day that also can affect the quantity of pollutants our actions will introduce into the environment. Heavily packaged foods, for instance, contain boxes, cartons, bottles etc.. made with polluting dyes, many of which are released from groundwater at municipal land fills. Whether we choose to drive to the corner store rather than walk or ride a bicycle will determine how much we personally contribute to acid and hydrocarbon emissions to the atmosphere (and ultimately to global fresh water supplies).

In the end, there are many choices on the personal and societal level that we must make (consciously or not) that affect the amount of pollution our town or country will be forced to live with. Our standard of living and very way of life is based upon practices which are inherently "dirtier" than those of our distant ancestors, although they too polluted their environment to some extent. Without taking a step backward in terms of our standards of living, the answer seems to lie in a combination of many small changes in our daily practices and paying more for goods and services, so that manufacturers of various materials and drivers of automobiles (for instance) will have cleaner devices with which to conduct their activities.

Pollution control:

The first defense against pollution involves public education and Industrial Monitoring. This is called Pretreatment. The Federal Government's role in pretreatment began with the passage of the Clean Water Act in 1972. The Act required the U.S. EPA to develop national standards to control industrial discharges into sewer systems. The standards are uniform national requirements which restrict the level of certain pollutants in the sewage from industries. All Publicly Owned Treatment Works must enforce the federal standards.

Treatment

Waste is treated at the Plant in a similar manner to that which occurs in nature. The objective in preliminary treatment is to remove the large debris, sand, and grit. During primary treatment, we remove a large percentage of the floatable and settleable material by physical methods. With secondary treatment we remove, and convert , biologically, contaminants remaining in the wastewater. The flow is then treated with chlorine to disinfect our effluent prior to discharge to the River.

During primary and secondary treatment, the removed solids (biosolids) are further processed by anaerobic digestion and prepared for land application. After a period of 15 - 30 days in the digester, the biosolids are forwarded to holding tanks and await land application.