Water Treatment This year Sidwell Friends School s and grade

Water Treatment This year, Sidwell Friends School’s 7th and 8th grade advisories were given the opportunity to take part in a service project. For our project, we chose to learn about the water we drink and use everyday. All 11 of us visited the Dalecarlia Water Treament Center close to our school in order to find the answers to the questions that we came up with. After visiting the Water Treatment Center, we decided to make a slideshow about our discoveries. Where does our water come from? • We all use water fountains and drink water from bottles, but have we ever thought about where our water comes from? We did some research and found that the main source is the Potomac Watershed. • R ock Creek, Melvin Hazen, and the Potomac rivers all drain into this watershed. The drainage area of the Potomac R iver is 1 4 ,700 square miles. Over 5 million people live in the Potomac watershed. This important watershed provides over 2,1 00 U S gallons per person every year. Melvin Hazen Potomac R iver Potomac R iver Potomac Watershed R ock Creek Dalecarlia Treatment Plant How is the water treated? • • • Now that we know what the source of the water is, we decided that we wanted to know how it gets to our houses and how the water is treated. We learned that it gets treated at Dalecarlia Water Treatment Center. Dalecarlia is located in Northwest Washington D.C., 5900 MacArthur Boulevard. It’s located near Spring Valley and the Palisades. On average, it processes 100,000,000 gallons a day in winter, but can reach over 200,000,000 gallons a day at times during July and August It is treated to remove solid objects and particles, to kill bacteria and other micro-organisms. In addition to removing contaminants, the water treatment process reduces the chemicals in the water distribution, and it adds fluoride for the prevention of tooth decay. It improves the overall taste and odor of the water as well. • How is the water treated cont. • • The water treatment at Dalecarlia works as follows: The water from Great Falls and Little Falls enters the reservoir of the Little Falls pump station and is sent to the Dalecarlia and McMillan Treatment Plants. A chemical coagulant, aluminum sulfate, is mixed into the water as it enters the sedimentation basins. When added to water, aluminum sulfate forms solid particles that attract other solid particles, creating large clumps called floc that settle out of the water as it passes through the sedimentation basins. In some of the basins, large paddles are used to mix the water so that the floc particles come in contact and stick together. Eventually, the water in each basin becomes basically clear as the floc settles out. The water then passes through filters. • • Each filter consists of anthracite coal, sand, gravel and then an under drain through which water flows. • With time, typically a few days, the filter becomes clogged with small particles and must be cleaned. Cleaning is done through the process of backwashing, or sending water backwards through filters to remove the small particles. The backwash water is recycled to be treated again. How is the water treated cont. • At times, the treatment plants add chlorine before and after going through the filters. This kills bacteria and other micro-organisms and reduces growth of algae in the system, thus extending the lifetime of the filters. Lastly, a variety of compounds are added to finish preparing the water for use. Chlorine and ammonia are added as a means of creating disinfectant residuals called chloramines. Orthophosphate is added as a corrosion inhibitor. Fluoride is added for the prevention of tooth decay. Lime is added to optimize the pH level of the water (From the Sidwell Environmental Stewardship Files). After the treatment center…. • After the Treatment Center • After the treatment center (Dalecarlia for us), the water is transferred to storage tanks. Sometimes chlorine or fluoride is inserted before the final storage process. The storage tanks can be aboveground (a water tower) or below (an underground reservoir). In highly populated areas such as DC, water is more likely to come from an underground reservoir. The water is then pumped from the water tower or reservoir through the distribution system. DC WASA (District of Columbia Water and Sewer Authority) is responsible for maintaining the cleanliness of the water and distribution system. For more information, visit: www.dcwasa.com www.epa.gov www.sidwell.edu • • • • • After cont. • The majority of DC’s water comes from the McMillan R eservoir. The reservoir was installed with a fast-flow sand filter in 1 98 5 . What about Medications and Chemicals in the Water? • Most of the large items that were initially in the water get caught by the filters, but chemicals, viruses, microbes, and drugs the Treatment Center has to test for, because these substances are not easily filtered out. Unfortunately, the people testing the water are not aware of all of the substances that are in it. The reason for this is that we don’t know what is being put in the water flowing into the Center. There are such low amounts of medications or chemicals that it is exceedingly difficult to find and extract them. However we do not know the long term effects of these unknown substances. Checking for certain things daily, like the Anthrax Virus is hard because testing for so many things would take extra time. Bioterrorism microbes and viruses are also rare, but if there is ever a threat of it, the Center starts testing immediately. With today’s knowledge and technology, our water is the absolute cleanest that it can be. Medicine and Chemicals Cont. Samples of water. One chemical checked in the water is e-coli. It is determined by putting the water into containers and shining a special light on it. Chemicals in beakers used to test water samples. Treated vs. Bottled • Once we learned how the water in our homes was treated, we wondered how bottled water is treated and which is better to drink. Bottled Water Bottled water undergoes disinfection by using ozone and ultraviolet technologies. They also may use treatment processes such as filtration, reverse osmosis or distillation. FDA regulations require the bottling companies to write anything they add on the label. However Federal Law does not require the companies to state what naturally occurring compounds are in the water, such as sulfates, sodium and radon. They’re also not required to state where the water came from and precisely how the water was treated. This means that bottled water could be the exact same from our taps which would result in the same problems from normal tap water, perhaps even greater ones. For example, if bacteria are not killed in the bottling companies treatments can grow in warm temperatures if it sits in a warm place for a long time. Which means purchased bottled water could be a potential danger. • VS.