Types of Water Pollution and their Sources

What do you see in this photo?

CK-12.org text and images logo The Ganges River is sacred to the people of India. It is also a major source of water for drinking and bathing for millions of people. An estimated 400 million people are affected by pollution in the Ganges. What can be done to protect a water body that has so much pressure placed on it?

Scarcity of Safe Drinking Water

The water that comes out of our faucets is safe because it has gone through a series of treatment and purification processes to remove contaminants. Those of us who are fortunate enough to always be able to get clean water from a tap in our home may have trouble imagining life in a country that cannot afford the technology to treat and purify water.

Pollution

Many people in the world have no choice but to drink from the same polluted river where sewage is dumped. One-fifth of all people in the world, more than 1.1 billion people, do not have access to safe water for drinking, personal cleanliness, and domestic use. Unsafe drinking water carries many pathogens, or disease-causing agents such as infectious bacteria, toxic chemicals, radiological hazards, and parasites.

Waterborne Disease

Photo of a foot with waterborne disease symptoms Waterborne disease caused by unsafe drinking water is the leading cause of death for children under the age of five in many nations and a cause of death and illness for many adults. About 88% of all diseases are caused by drinking unsafe water. Throughout the world, more than 14,000 people die every day from waterborne diseases, such as cholera, and many of the world's hospital beds are occupied by patients suffering from a waterborne disease.

Two children using special filtering straws to drink and avoid ingesting guinea worm Dracunculiasis, commonly known as Guinea Worm, is contracted when a person drinks the guinea worm larvae.

International aid can sometimes help to provide safe drinking water to people in regions where none is available. Sometimes wells are drilled to avoid contaminated surface waters.

Boys avoid guinea worm disease by drinking through a specially designed straw.

Is polluted water like this only seen in developing nations?

There is certainly polluted water in developed nations, but that water is cleaned and purified before it is put in taps and sent to people's homes. Pollutants come from a variety of sources.

Freshwater and ocean pollution are serious global problems that affect the availability of safe drinking water, human health, and the environment. Waterborne diseases from water pollution kill millions of people in underdeveloped countries every year.

Sources of Water Pollution

Water pollution contributes to water shortages by making some water sources unavailable for use. In underdeveloped countries, raw sewage is dumped into the same water that people drink and bathe in. Even in developed countries, water pollution affects human and environmental health.

Water pollution includes any contaminant that gets into lakes, streams, and oceans. The most widespread source of water contamination in developing countries is raw sewage. In developed countries, the three main sources of water pollution are described below.

Municipal Pollution

Wastewater from cities and towns contains many different contaminants from many different homes, businesses, and industries. Contaminants come from:

Sewage disposal (some sewage is inadequately treated or untreated).
Storm drains.
Septic tanks (sewage from homes).
Boats that dump sewage.
Yard runoff (fertilizer and herbicide waste).
Municipal and agricultural pollution.

Large numbers of sewage spills into San Francisco Bay are forcing cities, water agencies, and the public to take a closer look at wastewater and its impacts on the health of the bay.

Industrial Pollution

Factories and hospitals spew pollutants into the air and waterways (Image below). Some of the most hazardous industrial pollutants include:

Radioactive substances from nuclear power plants and medical and scientific sources.
Heavy metals, organic toxins, oils, and solids in industrial waste.
Chemicals, such as sulfur, from burning fossil fuels.
Oil and other petroleum products from supertanker spills and offshore drilling accidents.
Heated water from industrial processes, such as power stations.

Photo of foam in water indicating water pollution

Industrial Waste Water: Polluted water coming from a factory in Mexico. The different colors of foam indicate various chemicals in the water and industrial pollution.

Agricultural Pollution

Runoff from crops, livestock, and poultry farming carries contaminants such as fertilizers, pesticides, and animal waste into nearby waterways (image below). Soil and silt also run off farms. Animal wastes may carry harmful diseases, particularly in the developing world.

Photo of a chicken house

The high density of animals in a factory farm means that runoff from the area is full of pollutants.

Fertilizers that run off of lawns and farm fields are extremely harmful to the environment. Nutrients, such as nitrates, in the fertilizer, promote algae growth in the water they flow into. With the excess nutrients, lakes, rivers, and bays become clogged with algae and aquatic plants. Eventually, these organisms die and decompose. Decomposition uses up all the dissolved oxygen in the water. Without oxygen, large numbers of plants, fish, and bottom-dwelling animals die.

Fertilizer makes things grow. How could it cause a dead zone?

Image of a dead zone in the Gulf of Mexico as a result of fertilizer Fertilizer from farms and yards carried from the Mississippi River into the Gulf of Mexico creates an enormous dead zone, where algae use up all the oxygen and nothing else can live. The largest, in 2002, was about 22,000 square kilometers (8,400 mi²).

Ocean Pollution

Most ocean pollution comes as runoff from land and originates as agricultural, industrial, and municipal wastes. The remaining 20% of water pollution enters the ocean directly from oil spills and people dumping wastes directly into the water. Ships at sea empty their wastes directly into the ocean, for example.

In some areas of the world, ocean pollution is all too obvious.

Coastal pollution can make coastal water unsafe for humans and wildlife. After rainfall, there can be enough runoff pollution that beaches must be closed to prevent the spread of disease from pollutants. A surprising number of beaches are closed because of possible health hazards each year.

A large proportion of the fish we rely on for food live in the coastal wetlands or lay their eggs there. Coastal runoff from farm waste often carries water-borne organisms that cause lesions that kill fish. Humans who come in contact with polluted waters and affected fish can also experience harmful symptoms. More than one-third of the shellfish-growing waters of the United States are adversely affected by coastal pollution.

Dead Zones

Fertilizers that run off of lawns and farm fields are extremely harmful to the environment. Nutrients, such as nitrates, in the fertilizer, promote algae growth in the water they flow into. With the excess nutrients, lakes, rivers, and bays become clogged with algae and aquatic plants. Eventually, these organisms die and decompose. Decomposition uses up all the dissolved oxygen in the water. Without oxygen, large numbers of plants, fish, and bottom-dwelling animals die.

Every year dead zones appear in lakes and nearshore waters. A dead zone is an area of hundreds of kilometers of the ocean without fish or plant life.

The Mississippi is not the only river that carries the nutrients necessary to cause a dead zone. Rivers that drain regions where human population density is high and where crops are grown create dead zones all over the world (Figure below).

Map of dead zones around the world

Dead zones off the coasts. Red dots show the location and size of the dead zone; black circles show the location but the size is unknown. Darker blue regions of the oceans indicate that organic particulates are high and may lead to a dead zone.

How Pollutants Enter Groundwater

CK-12.org text and images logo Groundwater pollutants are the same as surface water pollutants: municipal, agricultural, and industrial. Groundwater is more susceptible to some sources of pollution. For example, irrigation water infiltrates into the ground, bringing with it the pesticides, fertilizers, and herbicides that were sprayed on the fields. Water that seeps through landfills also carries toxins into the ground. Toxic substances and things like gasoline are kept in underground storage tanks; more than 100,000 of the tanks are currently leaking and many more may develop leaks.

Photo of old gasoline tanks

Filtered Water

Photo of ground contamination Groundwater is a bit safer from some types of pollution than surface water from some types of pollution because some pollutants are filtered out by the rock and soil that water travels through as it travels through the ground, or once it is in the aquifer. But rock and soil can't get out everything, depending on the type of rock and soil and the types of pollutants. As it is, about 25% of the usable groundwater and 45% of the municipal groundwater supplies in the United States are polluted.

Pollutant Plume

When the pollutant enters the aquifer, contamination spreads in the water outward from the source and travels in the direction that the water is moving. This pollutant plume may travel very slowly, only a few inches a day, but over time can contaminate a large portion of the aquifer. Many wells that are currently in use are contaminated. In Florida, for example, more than 90% of wells have detectible contaminants and thousands have been closed.

Ground water diagram

RESOURCES IN THIS MODULE ARE OPEN EDUCATIONAL RESOURCES (OER) OR CREATED BY GAVS UNLESS OTHERWISE NOTED. SOME IMAGES USED UNDER SUBSCRIPTION.