Sources of Water Pollution
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C HAPTER
Chapter 1. Sources of Water Pollution
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Sources of Water Pollution
I can describe harmful human activities and how they affect an ecosystem.
Is the ocean a good dumping ground? Unfortunately some people think so. A lot of garbage ends up washing ashore, and some garbage stays floating out in the ocean. Animals can be strangled by floating trash or mistake inedible trash for food. Not only is the pollution of our oceans a problem, but also our precious freshwater resources are often polluted. Sources of Water Pollution
While to many people clean water may seem limitless and everywhere, to many others this is not so. Water pollution is a serious issue facing hundreds of millions of people world-wide, having harmful effects on the lives of those people. Water is not in unlimited supply and cannot just be made fresh when it is wanted. Water is actually a limited resource, and for many people, fresh, unpolluted water is hard to find. A limited resource is one that we use faster than we can remake it. It is a resource that can be used up. Water pollution happens when contaminants enter water bodies. Contaminants are any substances that harm the health of the environment or humans. Most contaminants enter the water because of humans. Surface water (river or lake) can be exposed to and contaminated by acid rain, storm water runoff, pesticide runoff, and industrial waste. This water is cleaned somewhat by exposure to sunlight, aeration, and microorganisms in the water. Groundwater (private wells and some public water supplies) generally takes longer to become contaminated, but the natural cleaning process also may take much longer. Groundwater can be contaminated by disease-producing pathogens, careless 1
www.ck12.org disposal of hazardous household chemical-containing products, agricultural chemicals, and leaking underground storage tanks.
FIGURE 1.1 Water pollution can cause harmful effects to ecology and human health. Shown is the pollution in Jakarta, Indonesia.
Natural events, like storms, volcanic eruptions and earthquakes can cause major changes in water quality. But human-caused contaminants have a much greater impact on the quality of the water supply. Water is considered polluted either when it does not support a human use, like clean drinking water, or a use for other animals and plants. The overgrowth of algae, known as an algal bloom, can result from the runoff of fertilizer into bodies of water. This excess of nutrients allows the algae to grow beyond control, bring harm to the rest of the ecosystem. The main sources of water pollution can be grouped into two categories: • Point source pollution results from the contaminants that enter a waterway or water body through a single site. Examples of this include untreated sewage, wastewater from a sewage treatment plant, and leaking underground tanks. • Nonpoint source pollution is contamination that does not come from a single point source. Instead, it happens when there is a buildup of small amounts of contaminants that collect from a large area. Examples of this include fertilizer runoff from many farms flowing into groundwater or streams. Do we have an infinite supply of drinkable water? No. In fact, in many parts of the world, finding clean drinkable water is difficult. This can lead to various serious health issues. Hundreds of millions of people world-wide are thought to live in areas where obtaining safe water is difficult. This makes preserving water resources an important global issue. Preserving Water Sources
It might seem like there is plenty of water on Earth, but that’s not really the case. Water is a limited resource . That means that it is used faster than it is replaced. Theoretically, at some point in time, the supply of fresh water could run out. Though this is unlikely, it is possible. But it is a significant issue in parts of the world with large populations. As these populations continue to grow, the supply of water becomes an increasingly important issue. Even though we have lots of water in our oceans, we cannot use that water whenever we want. It takes special equipment, such as a desalination plant, and a lot of energy (and money) to convert salt water into fresh water. Of all the water on Earth, only about 1% can be used for drinking water. Almost all of the rest of the water is either salt water in the ocean or ice in glaciers and ice caps. As a result, there are water shortages many places in the world. 2
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Chapter 1. Sources of Water Pollution
Since we have such a limited supply of water, it is important to preserve our water supplies. Therefore, steps have been taken to prevent water pollution. Technologies have also been developed to conserve water and prevent water pollution. Sub-Saharan African countries have the most vulnerable water supplies. Some scientists believe of a potential future crisis in both Asia and Africa from pollution and depletion of natural water resources. Many countries in the Middle East are at an extreme risk of water shortages. Diminished water supplies could increase the risk of both internal conflicts or wars between countries.
Preventing
In the U.S., concern over water pollution has resulted in many federal laws. Some of these laws go all the way back to the 1800s! The laws prohibit the disposal of any waste into the nation’s rivers, lakes, streams, and other bodies of water, unless a person first has a permit. Growing concern for controlling water pollutants led to the enactment of the Clean Water Act in 1972. The Clean Water Act set water quality standards. It also limits the pollution that can enter the waterways. Other countries are also actively preventing water pollution and purifying water.
Wastewater Treatment
Fresh water is also preserved by purifying wastewater. Wastewater is water that has been used for washing, flushing, or manufacturing. It includes the water that goes down your shower drain and that is flushed down your toilet. Instead of dumping wastewater directly into rivers, wastewater can be purified at a water treatment plant. When wastewater is recycled, waterborne diseases caused by pathogens in sewage can be prevented. What are some ways you can save water in your own house?
FIGURE 1.2 Sewage treatment plant.
Vocabulary
• limited resource: Resource that is used faster than it can be made. • groundwater: Underground water reserves. • water pollution: Pollution due to contaminants entering the water supply. 3
www.ck12.org Summary
Practice
Use the resource below to answer the questions that follow. • Water Pollution at http://www.youtube.com/watch?v=ACgv19b-n5E (4:42)
1. How can human sewage throw ecosystems out of balance? What nutrient cycle(s) are involved? 2. How does agriculture run-off effect ecosystems? How does this change move through the food web? What can the result be? 3. How can drugs excreted by humans affect aquatic organisms? How does this affect the ecosystem? 4. What is heat pollution? What affect can this have on aquatic ecosystems? Explain your answer as fully as possible.
Review
1. 2. 3. 4. 5.
Why is fresh water a limited resource? What is water pollution? What are two main sources of pollution of surface water? What are two main sources of groundwater pollution? What’s the difference between a point source and nonpoint source of water pollution?
Missouri Standard(s):
• 4.1.D.a: Describe beneficial and harmful activities of organisms, including humans (e.g., deforestation, overpopulation, water and air pollution, global warming, restoration of natural environments, river bank/coastal stabilization, recycling, channelization, reintroduction of species, depletion of resources), and explain how these activities affect organisms within an ecosystem • 4.1.D.b: Predict the impact (beneficial or harmful) of a natural environmental change (e.g., forest fire, flood, volcanic eruption, avalanche) on the organisms in an ecosystem • 5.3.A.b: Describe the effect of human activities (e.g., landfills, use of fertilizers and herbicides, farming, septic systems) on the quality of water 4
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Chapter 1. Sources of Water Pollution
References 1. Stephen Codrington. Water pollution causes detrimental effects to both ecology and human health. CC BY 2.5 2. . Processing wastewater before dumping it into rivers helps conserve fresh water. 3. . Processing wastewater before dumping it into rivers helps conserve fresh water.
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