Water pollution refers to any substance introduced into a body of water that negatively impacts the surrounding species or ecosystem. This can be caused by both intentional and accidental actions.
Pollutants can include chemicals, microorganisms and even garbage. Since water is a natural solvent, it easily absorbs many of these substances.
Sources of Water Pollution
Water pollution can be caused by a wide range of human activities. The pollutants can be organic – such as medical, industrial and household wastes; or inorganic, such as chemicals and metals. Pollution can also include both thermal and biological contaminants. Thermal pollution includes discharging hot water into bodies of water, which can cause a significant drop in the amount of dissolved oxygen and kill fish. Other thermal pollution sources include the discharge of cooling waters from power plants and the rise in water temperatures due to global warming.
Most water pollution is caused by human activities, including sewage discharges, chemical spills, agricultural runoff, and the release of harmful microorganisms. In many parts of the world, untreated sewage is disposed into rivers and oceans, contaminating water with bacteria and other microorganisms.
In addition, the use of fertilizers in agriculture can lead to excessive nutrient levels in lakes, rivers, and oceans, which is called eutrophication. This can result in the death of fish and other marine life, as well as causing algal blooms that are harmful to humans.
Other sources of water pollution include the disposal of toxic wastes into lakes, rivers, and streams; the release of radioactive materials into bodies of water; and the discharge of oil into bodies of water. Every year, unsafe drinking water sickens more than a billion people worldwide and contributes to the deaths of hundreds of thousands of children. This is because the pathogens in contaminated water can cause diseases such as typhoid fever, cholera, and giardiasis.
Biological contaminants, such as bacteria and viruses, pollute water by entering ecosystems that are harmful or even deadly to humans. This type of pollution degrades water quality and reduces its usefulness. It can also cause water-borne diseases such as cholera and giardia, which can sicken humans. In fact, unsafe drinking water is a leading cause of disease worldwide, especially in poorer nations.
Waste from human and animal sources is a major contributor to water pollution. This includes feces from open defecation and sewage systems without proper disinfection, pesticides that wash into waterways when it rains, agricultural runoff and animal waste that pollute rivers and lakes, untreated leachates from landfills and leaking underground storage tanks below gasoline service stations.
Many of these same pollutants can also enter groundwater, which can then be a source of drinking water for people. Some of the main causes include septic tank failure, untreated industrial waste discharge, landfill leachates and the dumping of toxic chemicals such as polychlorinated biphenyls (PCBs) and trichloroethylene into soil and water.
Another major problem is thermal pollution, which occurs when heated waters destroy aquatic life and lower dissolved oxygen levels. Rising water temperatures from global warming are a big factor in this, as are cooling towers at power plants and the discharge of heat-treated sewage into rivers. In addition, wind-blown debris can also become a source of pollution.
The water we use comes from natural sources, but it also flows through and interacts with the human-made world. Water is a great solvent and dissolves many substances, which makes it prone to contamination by chemicals that aren’t naturally occurring in the environment.
The majority of chemical pollutants in water come from human activities like the manufacturing, handling, storing and disposal of various chemicals. This can include dumping of industrial and municipal wastewater (also called effluent) at power plants, oil refineries and other facilities, construction, mining and smelting activities, transportation and the application of agricultural pesticides and herbicides.
These chemicals can be in the form of toxic substances like metals such as lead, mercury and arsenic, plastics or synthetic chemicals. The degradation of water quality due to the presence of these contaminants leads to diseases like cholera, diarrhoea, dysentery, etc.
In addition, chemical pollutants in water can be in the form of nonpoint source pollution or point source pollution. Point source pollution is contamination that emanates from a single identifiable location, like a factory outlet or an oil spill. Nonpoint source pollution, on the other hand, is pollution that affects an entire watershed and cannot be traced to a specific site.
One of the largest concerns regarding water pollution is the phenomenon known as transboundary pollution, which occurs when contaminated water from one country spills over into another. This can be the result of a disaster such as an oil spill, or it could be the slow, downriver creep of industrial and agricultural wastewater from cities, towns and farms.
Water pollution is caused by substances that pollute a body of water. This can include chemicals, bacteria and trash. All forms of pollution can affect the health and safety of the water supply. The chemical pollutants are often toxic to the plants and animals that live in the water. The bacteria and trash can cause diseases in humans. The trash and bacteria may also make the water unhealthy to drink.
The physical pollutants are mainly sediments, metals and organic compounds. The sediments are washed into the water by rain or from erosion of soil. The metals and organic compounds can be deposited in the water by human feces, improperly disposed waste or from sewage systems with inadequate disinfection steps. The contaminants can also be dissolved from poorly designed hazardous waste sites or from industrial processes such as metal smelting, oil refining and production of paper. Chlorinated solvents such as polychlorinated biphenyls (PCBs), trichloroethylene and carbon tetrachloride are a problem because they sink in the water and are highly toxic.
The other major physical source is the discharge of warm water from power plants and factories that pollutes natural bodies of water. This can lead to cultural eutrophication by promoting algal blooms that can be harmful to fish. The discharged water is often accompanied by foam, garbage and floating debris. Nonpoint source pollution, or diffuse contamination, is another large contributor to water pollution. This is because it is difficult to trace the pollutant back to a single point of source.