Water Pollution

Do you live near water? Do you see pollution?

Water pollution is a worldwide problem. Almost anything released into the air or onto the land can end up in Earth’s water.

Surface Water Pollution

Water pollution may come from one source. For example, chemicals from a factory may empty into a stream. Water pollution may come from more than one source, too. For example, chemicals in the air may be absorbed in rainwater and fall into that same stream. It is much more difficult to control pollution from more than one source.

In the developed nations there are three main sources of water pollution:

1. Agriculture
2. Industry
3. Municipal, or community

Agriculture

Chemicals that are applied to farm fields include fertilizers and pesticides. Excess chemicals can be picked up by rainwater. The chemicals can end up in streams, ponds, lakes, or the ocean. Dissolved fertilizer causes tremendous numbers of water plants and algae to grow. This can lead to dead zones where nothing can live in lakes or the coastal oceans.

Waste from livestock can also pollute water. The waste contains pathogens that can cause diseases. Many farms in the U.S. have thousands of animals. These farms produce millions of gallons of waste. The waste is stored in huge lagoons, like the one pictured below (Figure below). Many leaks from these lagoons have occurred.

Industry

Factories and power plants may pollute water with harmful substances.

• Many industries produce toxic chemicals.
• Nuclear power plants produce radioactive wastes.
• Oil tanks and pipelines can leak.

Municipal

“Municipal” refers to the community. Households and businesses in a community can pollute the water supply. Municipal pollution comes from sewage, storm drains, septic tanks, boats, and runoff from yards. For example:

• People apply chemicals to their lawns. The excess can run off into surface waters.
• People may dispose of harmful substances incorrectly. For example, motor oil must not be drained into a storm sewer.
• Municipal sewage treatment plants dump treated wastewater into rivers or lakes. But the wastewater may not be treated for everything, or it may not be treated enough.

Science Friday: Poop and Paddle: An Eco-Friendly Floating Toilet

How do wetlands filter water? In this video by Science Friday, inventor Adam Katzman describes how his toilet-boat converts human waste into cattails and clean water.

Summary

• Pollution enters water from municipal, industrial, and agricultural sources.
• Fertilizer runoff can create dead zones in the ocean.
• People pollute water when they apply excess chemicals to their lawn. They may also dispose of pollutants incorrectly.

Review

1. Why do large animal farms cause a lot of pollution?
2. What are the three major sources of water pollution in the developed world?
3. How can you and your family reduce water pollution?