When you fill a glass at your kitchen sink for a drink, you probably don't think about where the water came from. Perhaps you sh
ould, though, because the water you drink affects your health. Consider the small town of Long Pine, Nebraska. Less than a mile from town, Long Pine Creek is fed by a wealth of underground water. When the town was built, the people of Long Pine dug a well near the creek. They installed a pump and piped the water into town. They also built a water tower to keep the water pressure even. 2 Many people who live near an aquifer get their water in this manner. An aquifer is an underground source of water. When people dig down to the level of the aquifer, water from the ground flows into the well. Some aquifers, like the one near Long Pine, are naturally clean and free from harmful chemicals, minerals, and microbes. But many aquifers are not of such good quality. Some are tainted by ammonia or bacteria. Some contain poisonous minerals such as arsenic, and some have too many minerals in them (such as salt or iron) for the water to be fit to drink. 3 Most major cities in the United States get their water from lakes or rivers. Water from lakes, rivers, or contaminated aquifers must be treated. The process is carried out in a treatment plant. Drinking water has to be free of harmful minerals, poisonous chemicals, and disease-causing bacteria. In addition, it must be acid-neutral or slightly alkaline to prevent contamination from metal in the pipes. 4 The city of York, Pennsylvania, gets its water from two artificial lakes, called reservoirs, which are filled by Codorus Creek. The water looks clear, but if you dipped a glass in it, you would see mud, organic particles, and maybe even a minnow or a dead leaf. You wouldn't want to drink it! The water goes through a screen to remove the dead leaves and aquatic animals. Then it goes to a pumping station. At the pumping station, a chemical called potassium permanganate is added to increase the amount of oxygen in the water. Oxygen helps kill germs and improves water's taste. 5 From the pumping station, the water goes to a rapid mixer. Here an ingredient called alum is added to make fine particles clump together. Powdered carbon is also added at this stage. The alum gets rid of cloudiness in the water by causing the tiny particles to settle out when the water is pumped to a settling basin. The carbon, which also settles out, absorbs bad odors and tastes. On its way to the settling basin, the water gets an injection of chlorine. 6 The water stays in the basin while the particles, called "floc," sink to the bottom. Afterward, the almost-clear water passes through a filter with layers of sand, charcoal, and gravel. The filter takes out all but the tiniest pieces. The water is then sent to a clearwell, where ammonium sulfate, lime, and additional sodium hypochlorite are added. Finally, it is pumped into storage tanks until people need to use it. As it flows out to homes, factories, and businesses, caustic soda is added to control the water's acidity. This is an important step; if the water is too acidic, it may react with the metal surface of water pipes and pick up some of the metal. 7 In some coastal areas around the world, including California, desalinization plants are being built. These plants remove the salt from ocean water so that people can drink it. Salt can be removed by distillation or by reverse osmosis (pumping seawater at high pressure against a special membrane). Such plants can produce twenty-five million gallons of drinking water a day, but they are expensive to build and may harm the ocean. 8 Windhoek, the capital city of Namibia, is located between two deserts, so it has a constant water shortage. The city has developed a method so that waste water from the city's sewage-treatment plant can be reused. Advanced treatments remove ammonia and dissolved organic material. The water is purified by adding chlorine and lime. Normally, the reclaimed water irrigates parks and gardens, but during droughts, as much as thirty percent of the clean water pumped into homes comes from reclaimed water. Water shortages can be severe in some areas of the world, so we should continue working to find better methods of conserving and reusing our water supplies. Question 1 Which statement would be included in a summary of the passage? A Many people who live near aquifers get their water from wells. B Water from lakes and rivers may look clean, but it can be full of microbes and minerals. C Ammonium sulfate, lime, and other chemicals are added to drinking water during processing. D Desalinization plants remove salt from ocean water to make it safe for drinking.
