1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Using Water Wisely Bellringer While hiking, you realize your canteen is almost empty. Why should you not fill the canteen with water from a nearby stream? Chapter 11

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Using Water Wisely Chapter 11 Identify two forms of water pollution. Explain how the properties of water influence the health of a water system. Describe two ways that wastewater can be treated. Describe how water is used and how water can be conserved in industry, in agriculture, and at home. Objectives

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Using Water Wisely Chapter 11 Water Pollution What Is Pollution? Pollution is the introduction of harmful substances into the environment. Pollution that comes from one specific site is called point-source pollution. Nonpoint-source pollution is pollution that comes from many sources. What type of pollution is the hardest to control?

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Using Water Wisely Chapter 11 Health of a Water System Dissolved Oxygen Fish and other organisms that live in water need dissolved oxygen in the water to live. Pollutants such as sewage, fertilizer runoff, and animal waste can decrease DO levels. Temperature changes also affect DO levels. Thermal pollution can decrease DO levels.

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Using Water Wisely Chapter 11 Health of a Water System Nitrates Elevated nitrate levels in water can be harmful to organisms because they lower the amount of dissolved oxygen in the water. Alkalinity Alkalinity refers to water’s ability to neutralize acid. Acid rain can lower water’s alkalinity.

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Using Water Wisely Chapter 11 Cleaning Polluted Water Sewage treatment plants are facilities that clean the waste materials out of water. Primary Treatment In primary treatment, dirty water is passed through a large screen to catch solid objects. Secondary Treatment In secondary treatment, the water is sent to an aeration tank, where it is mixed with oxygen and bacteria.

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Using Water Wisely Chapter 11 Cleaning Polluted Water

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Using Water Wisely Chapter 11 Cleaning Polluted Water A septic tank is a large underground tank that cleans wastewater from a household. Wastewater flows from the house into the tank, where the solids sink to the bottom. Bacteria break down these wastes on the bottom of the tank. The water flows from the tank into a group of buried pipes, called a drain field, to distribute the water.

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Using Water Wisely Chapter 11 Cleaning Polluted Water

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Using Water Wisely Chapter 11 How Do You Use Water? The average household in the United States uses about 100 gal of water per day. This circle graph shows some common uses of these 100 gal. Many people save water by installing low-flow shower heads and low- flush toilets. What percentage of water in our homes is used for drinking?

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Using Water Wisely Chapter 11 Where the Water Goes About 19% of water used in the world is used for industrial purposes. Much of the water can be recycled. Water must be used in agriculture to facilitate plant growth. Most of the water that is lost during farming is lost through evaporation and runoff. How does the drip irrigation system help conserve water?

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 4 Using Water Wisely Chapter 11 Point-source pollution and nonpoint-source pollution are two kinds of water pollution. Pollutants can decrease oxygen levels and increase nitrate levels in water. These changes can cause harm to plants, animals, and humans. Wastewater can be treated by sewage treatment plants and septic systems. Water can be conserved by using only the water that is needed, by recycling water, and by using drip irrigation systems. Section Summary