Causes of Water Pollution:

     Water pollution is one of the most serious environmental problems. It occurs when water is contaminated by such substances as human and animal wastes, toxic chemicals, metals, and oils. Pollution can affect rain, rivers, lakes, oceans, and the water beneath the surface of the earth. Pollution isn't always obvious, so many people don't seem to notice. There are three chief sources of water pollution. These sources are:
    (1) industrial wastes
    (2) sewage
    (3) agricultural chemicals and wastes

Diagram of unhealthy water system. (Diagram taken from World Book)

  1. Industrial Wastes: Many industrial countries around the world discharge pollutants that are toxic and very harmful to the environment. Industries discharge much chemical waste directly into natural bodies of water. Many factories in the US use water from rivers in their cooling systems. When the water is returned to the rivers, the temperature of the water can be up to 10 degrees or warmer creating catastrophes for the marine life. In addition, the burning of coal, oil, and other fuels by power plants, factories, and motor vehicles releases sulfur and nitrogen oxides into the air. These pollutants cause acid rain, which enters streams and lakes.
    High levels of mercury have been found in fish far from industrial areas. The main sources of the mercury appear to be emissions to the atmosphere from coal-fired boilers, municipal incinerators, and smelters.

  2. Sewage: Sewage consists of human wastes, garbage, and water that has been used for laundering or bathing. In many countries in the world, including our own, raw sewage is piped right into river, lakes, and oceans. Most of the sewage in the United States goes through treatment plants that remove solids and such dissolved substances as the nutrients nitrogen and phosphorus. Grey water, the water we use to bathe ourselves, and the water that we wash our dishes with, can create potentially large problems for plants and animals.
    About 25 percent of the households of the United States use septic tank systems, which pass the sewage through tanks and filter it through leaching fields into the land. Some sewage in the United States still goes untreated directly into waterways or the ocean. However, government regulations control the amount and the quality of the discharge.

  3. Agricultural chemicals and wastes: Water from rain or melted snow flows from farmland into streams, carrying chemical fertilizers and pesticides that farmers have used on the land. Animal wastes also can cause water pollution, particularly from feed lots with many animals. Cattle, hogs, sheep, and poultry raised on feed lots do not distribute their wastes over widespread pastureland. Instead, much of their wastes runs off into nearby streams. Water used for irrigation also may be polluted by salt, agricultural pesticides, and toxic chemicals on the soil surface before it flows back into the ground.

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    Water polluted with human and animal wastes can spread typhoid fever, cholera, dysentery, and other diseases. Most of the water in the U.S. is disinfected with chlorine to kill disease-causing germs. However, disinfecting does not remove harmful chemical compounds, such as polychlorinated biphenyls (PCB's) and chloroform, or harmful metals, such as arsenic, lead, and mercury. Sometimes, when chemicals seep into ground water, people who have pumps, pump up the water and then drink the water that is contaminated. The careless release of such toxic wastes, primarily into waste dumps, threatens ground water supplies. PCB's, chloroform, and pesticides have been found in some municipal drinking water. Scientists are concerned that drinking even small quantities of these substances over many years may have harmful effects.
    Pollution prevents people from enjoying some bodies of water for recreation. For example, odors and floating debris make boating and swimming unpleasant, and the risk of disease makes polluted water unsafe. Oil spilled from ships or offshore wells may float to shore. It can kill water birds, shellfish, and other wildlife. This creates a terrible problem, not only for animals but for people. Much of the worlds population lives near the sea, and commercial fishing is a very important industry for sea fairing people. When water becomes contaminated, it can kill entire populations of fish.
    Algae blooms can be triggered by the run off of certain phosphates that farmers use. These phosphates are rich in nutrients and can trigger blooms of algae. The algae then covers up the pond so that no light enters. The plants on the bottom die from lack of exposure to the sun. The algae also consume huge amounts of oxygen and just suck it right out of the water. This can kill the fish and other aquatic life in the pond, making the pond literally dead.

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    Sewage treatment is among one of the most efficient ways to help purify water before it enters streams.

Diagram of a healthy water system. (Diagram taken from World Book)

    In 1974, the U.S. Congress passed the Safe Drinking Water Act to help protect the nation's public water supply against pollution. This act authorized the Environmental Protection Agency (EPA) to establish uniform quality standards for more than 200,000 public water systems throughout the United States. The standards were designed to reduce the amount of harmful bacteria, chemicals, and metals in drinking water. The EPA and the state governments began to enforce the standards in 1977.

What can you do?

    You can help by not dumping trash into lakes and streams.

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