Water Quality and Contamina on 22 x Usable water x Ground water x Surface water x Ground water contaminates x Water treatment x Drinking water quality Figure 1: At any given moment, 97% of the planet’s water is in oceans. Only a small fraction of the remaining freshwater is usable by humans, underscoring the importance of treating our wa- ter supply with care. It is no secret that water is one of the most valuable resources on Earth. Every plant and animal requires wa- ter to survive, not only for drinking, but also for food production, shelter creation, and many other necessities.
Water has also played a major role in transforming the earth’s surface into the varied topography we see to- day. While more than 70% of our planet is covered in water, only a small percentage of this water is usable fresh- water. The other 99% of water is composed primarily of salt water, with a small percentage being composed 23 of glaciers. Due to the high costs involved in transforming salt water into freshwater, the earth’s population survives off the less than 1% of freshwater available. Humans obtain freshwater from either surface water or groundwater. Surface water is the water that collects on the ground as a result of precipitation. The water that does not evaporate back into the atmosphere or infiltrate into the ground is typically collected in rivers, lakes, reser- voirs, and other bodies of water, making it easily accessible. Groundwater, on the other hand, is located underneath the ground. This water is stored in pores, fractures, and other spaces within the soil and rock underneath the surface. Precipitation, along with snowmelt, infil- trates through the ground and accumulates in available underground spaces. Aquifers are areas in which water collects in sand, gravel, or permeable rock from which it can be extracted for usable freshwater. The depth of aquifers varies from less than 50 feet to over 1,500 feet below the sur- face. The water within an aquifer typically does not flow through, as it would through a river or stream, but in- stead soaks into the underground material, similar to a sponge. As aquifers are depleted by human use, they are also recharged from precipitation seeping into the ground and restoring the water level. However, many times the recharge of the aquifers does not equal the amount of water that has been extracted. If that cycle continues, the aquifer will eventually dry up and will no longer be a viable source of groundwater. Evapora Ÿon Cloud forma Ÿon Precipita Ÿon Groundwater Evapora Ÿon Transpira Ÿon Precipita Ÿon Precipita Ÿon Figure 2: Water is a renewable source, purified and delivered across the planet by the hydrological cycle. 24 While the water that precipitates in the form of rain is relatively pure, it does not take long for it to pick up con- taminants. There are natural, animal, and human-made sources of water pollutants. They can travel freely from one location to another via streams, rivers, and even groundwater. Pollutants can also travel from land or air into the water. Groundwater contamination most often occurs when human-made products, such as mo- tor oil, gasoline, acidic chemicals, and other substances, leak into aquifers and other groundwater storage areas. The most common source of contaminants come from leaking storage tanks, poorly maintained land- fills, septic tanks, hazardous waste sites, and the common use of chemicals, such as pesticides and road salts. The dangers of consuming contaminated water are high. Many deadly diseases, poisons, and toxins can reside in contaminated water supplies, severely affect- ing the health of those who drink the water. It is also believed that an increased risk of cancer may result from ingesting contaminated groundwater. With the many contaminants that can infiltrate our wa- ter supply, it is crucial that there be a thorough water treatment plan in place to purify the water and make it drinkable. While each municipality has its own water treatment facility, the process is much the same at each location.
The process begins with aeration, in which air is added to the water to let trapped gases escape while increasing the amount of oxygen within the water. The next step is called coagulation or flocculation, in which chemicals, such as filter alum, are added to the incoming Water is the only substance that is found naturally in three forms: solid, liquid, and gas If the entire world’s supply of water could fit into a one- gallon jug, the fresh water available to use would equal less than one tablespoon Approximately 66% of the human body consists of wa- ter - it exists within every organ and is essential for its function Figure 3: Sedimentation tanks, such as those shown above, are used to settle the sludge and remove oils and fats in sewage. This step can remove a good por- tion of the biological oxygen demand from the sew- age, a key step before progressing with the treat- ments and eventually releasing into the ground or body of water. 25 water and then stirred vigorously in a powerful mixer. The alum causes compounds, such as carbonates and hydroxides, to form tiny, sticky clumps called floc that attract dirt and other small particles. When the sticky clumps combine with the dirt, they become heavy and sink to the bottom. In the next step, known as sedimentation, the heavy particles that sank to the bottom during coagulation are separated out and the remaining water is sent on to filtration. During filtration, the water passes through filters made of layers of sand, charcoal, gravel and pebbles that help filter out the smaller particles that have passed through until this point. The last step is called disinfection, in which chlorine and/or other disinfectants are added to kill any bacteria that may still be in the water. At this point, the water is stored until it is dis- tributed through various pipes to city residents and businesses. After the water goes through the treatment process, it must also pass the guidelines stated in the Safe Drinking Water Act, in which various compo- nents are tested to ensure that the quality of the water is sufficient for drink- ing. There are currently over 65 contaminants that must be monitored and maintained on a regular basis to keep local drinking water safe for the public. Some of these chemical regulations include lead, chromium, selenium, and arsenic. Other components, such as smell, color, pH, and metals, are also monitored to ensure residents are provided clean and safe drinking water. Figure 4: Fresh water is essen- tial to humans and other land- based life. Contaminated water must be treated before it can be released into the water supply. 26 Bottled water is a billion dollar industry in the United States. Still, few people know the health benefits, if any, that come from drinking bottled water as opposed to tap water. This experiment will look at the levels of vari- ous different chemical compounds in both tap and bottled water to determine if there are health benefits in drinking bottled water.
1. Before beginning, record your hypothesis in post-lab question 1 at the end of this procedure. Be sure to indicate which water source you believe will be the dirtiest and which water source will be the cleanest.
2. Label three 250 mL beakers Tap Water, Dasani ®, and Fiji ®. Pour 100 mL of each type of water into the corresponding beakers. 3. Locate the ammonia test strips. Begin by placing a test strip into the Tap Water sample and vigorously moving the strip up and down in the water for 30 seconds, making sure that the pads on the test strip are always submerged. Dasani ® bottled water Fiji ® bottled water Jiffy Juice Ammonia test strips Chloride test strips 4 in 1 test strips Phosphate test strips Iron test strips (3) 250 mL Beakers (3) 100 mL Beakers (1) 100 mL Graduated Cylinder Permanent marker Stopwatch Parafilm ® Pipettes (3) Foil packets of reducing powder *Tap water *You must provide 27 4. Remove the test strip from the water and shake off the excess water.
5. Hold the test strip level with the pad side up for 30 seconds.
6. Read the results by turning the test strip so the pads are facing away from you. Compare the color of the small pad to the color chart at the end of the lab. Record your results in Table 1.
7. Repeat the procedure for both Dasani ® and Fiji| ® bottled water. Record your results for both in Table 1. 8. Locate the chloride test strips. Begin by immersing all the reaction zones (“the pads”) of a test strip in the Tap Water sample for 1 second.
9. Shake off the excess liquid from the test strip. After 1 minute, determine which color row the test strip most noticeably coincides with on the color chart at the end of the lab. Record your results in Table 2. 10. Repeat the procedure for both Dasani ® and Fiji ® bottled water. Record your results for both in Table 2. 11. Locate the 4 in 1 test strips. Begin by dipping a test strip in the Tap Water for 5 seconds with a gentle back and forth motion. 12. Remove the test strip from the water and shake once, briskly, to remove the excess water.
13. Wait 20 seconds and use the color chart at the end of this lab to match the test strip to the Total Alkalini- ty, Total Chlorine, and Total Hardness on the color chart. Be sure to do all of the readings within seconds of each other. Record your results in Table 3.
Note: You will not be using the pH reading obtained from the 4 in 1 test strips. The pH will be determined at the end of this experiment using a different method. 14. Repeat the procedure for both Dasani ® and Fiji ® bottled water. Record your results for both in Table 3. 15. Locate the phosphate test strips. Begin by dipping a test strip into the Tap Water for 5 seconds.
16. Remove the test strip from the water and hold it horizontally with the pad side up for 45 seconds. D o not shake the excess water from the test strip. 28 17. Compare the results on the pad of the test strip to the color chart at the end of this lab. Record your re- sults in Table 4.
18. Repeat the procedure for both Dasani ® and Fiji ® bottled water. Record your results for both in Table 4.
19. Now, label the three 100 mL beakers Tap Water, Dasani ®, and Fiji ®. Use the 100 mL graduated cylinder to measure 30 mL of the Tap Water from the 250 mL beaker. Pour the Tap Water into the 100 mL beaker.
Repeat these steps for the Dasani ® and Fiji ® bottled water. 20. Beginning with the Tap Water, open one foil packet of reducing powder and add it to the 100 mL beaker.
Cover the beaker with a piece of Parafilm ® and shake the beaker vigorously for 15 seconds. 21. Locate the iron test strips. Remove the Parafilm ® and dip the test pad of an iron test strip into the Tap Wa- ter sample, rapidly moving it back and forth under the water for 5 seconds. 22. Remove the strip and shake the excess water off. After 10 seconds, compare the test pad to the color chart at the end of this lab. If the color falls between two colors on the color chart, estimate your result.
Record your results in Table 5. 23. Repeat the procedure for both Dasani ® and Fiji ® bottled water. Record your results for both in Table 5. 24. Use your 100 mL graduated cylinder to measure and remove 45 mL of the Tap Water from the 250 mL beaker. Discard this water. Your 250 mL beaker should now contain 25 mL of Tap Water. Repeat these step with the Dasani ® and Fiji ® bottled water.
25. Use a pipette to add 5 mL of Jiffy Juice to the Tap Water. Mix gently with the pipette or by swirling the liq- uid. 26. Compare the color of the Tap Water to the pH chart in the key. Record the pH in Table 6.
27. Repeat the procedure with both the Dasani ® and Fiji ® bottled water and record your results in Table 6 29 0 10 30 60 100 200 400 0 500 1000 1500 2000 ≥3000 Ammonia (mg/L) Chloride (mg/L) 4-in-1 Test Strip:
*Note there are 4 pads on this test strip. From top to bottom (with the bottom of the strip being the handle), the pads are: pH, Chlorine, Alkalinity, and Hardness. Remember that the pH is not to be measured using the strip. pH Chlor. Alk. Hard. 0 0.2 1.0 4.0 10.0 0 40 80 120 180 240 500 0 50 120 250 425 1000 Soft Hard Very Hard Total Chlorine (mg/L) Total Alkalinity (mg/L) Total Hardness (mg/L) 30 0 0.15 0.3 0.6 1 2 5 0 10 25 50 100 Phosphate (ppm) Total Iron (ppm) pH 1-2 3 4 5 6 7 8 9 10 11-12