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| Water from both public and private supplies often needs some treatment to ensure that the water is | afe and appealing to drink. |
| water quality | The degree of purity of water, determined by measuring the substances in water, besides water molecules. |
| pH | How acidic or basic a substance is, measured on a scale of 1 (very acidic) to 14 (very basic). |
| hardness | The level of the minerals calcium and magnesium in water. |
| concentration | The amount of one substance in a certain volume of another substance. |
| filtration | The process of passing water through a series of screens that allow the water through, but not larger solid particles. |
| flocs | Sticky globs created by adding a chemical such as alum during water treatment. |
| coagulation | The process by which particles in a liquid clump together; a step in the water treatment process. |
| sewage | Water containing human wastes. |
| Most communities treat their wastewater to | make it safe to return to the environment. |
| sludge | Deposits of fine solids that settle out from wastewater during the treatment process. |
| septic tank | An underground tank containing bacteria that treats wastewater as it passes through. |
| leach field | The ground area around a septic tank through which wastewater filters after leaving the tank. |
| A water shortage occurs when there is | too little water or too great a demand in an area—or both. |
| drought | A water shortage caused by long periods of low precipitation in a particular area. |
| conservation | The process of using a resource wisely so it will not be used up. |
| Reducing water use, recycling water, and reusing water are | three major forms of water conservation by industries. |
| desalination | The process of obtaining fresh water from salt water by removing the salt. |
| water pollution | The addition of any substance that has a negative effect on water or the living things that depend on the water. |
| The major sources of water pollution are | human wastes, industrial wastes, agricultural chemicals, and runoff from roads. |
| point source | A specific source of pollution that can be identified, such as a pipe. |
| nonpoint source | A widely spread source of pollution, such as road runoff, that is difficult to link to a specific point of origin. |
| acid rain | Rain that is more acidic than normal, caused by the release of molecules of sulfur dioxide and nitrogen oxide into the air. |
| The rich supply of nutrients from fertilizers encourages the | growth of plants and algae in and around nearby bodies of water. |
| pesticide | A chemical intended to kill insects and other organisms that damage crops. |
| Living things in lakes, streams, and wetlands filter out and break down | waste materials. |
| kinetic energy | The form of energy an object has because of its motion. |
| potential energy | Energy that is stored and available to be used later. |
| hydroelectric power | Electricity produced by the kinetic energy of water moving over a waterfall or dam. |
| Hydroelectric power plants capture the kinetic energy of | moving water and change it into electrical energy. |
| Hydroelectric power is clean, safe, and efficient. Although building a dam is expensive, the water is | free and is naturally renewed by the water cycle |
