Where does our water come from?
When I imagined living in a remote place like Antarctica, I pictured a rugged life without the conveniences that I have at home. However, there are many aspects of life here at McMurdo that are similar to the U.S. Today I learned more about one such convenience: running water. I visited the water treatment plant today and discovered how McMurdo station is able to provide clean water to its inhabitants every day.
Paul Jones greets Michelle Brown to give her a tour of the water treatment plant at McMurdo Station.
Paul Jones, who operates the water plant, invited me to tour the facility. Someone has to monitor the water tanks every day to make sure they do not run out or overflow. There are four giant water tanks that hold 50,000 gallons of water each. While one tank is emptying out, another tank is being filled and treated.
The red marker in the tube shows the current water level in the water tank, while the penguin marks when the tank will be full.
Warming the Water
The water is taken directly from McMurdo Sound through a pump. Thankfully, it is upstream from the sewage treatment plant's output pipe. Ocean water is cold--it is around 20 - 25 degrees Fahrenheit. Fresh water freezes at 32 degrees Fahrenheit. If the water were treated at its initial temperature, it would freeze once the salt was taken out of it! Before the water is treated, it is heated to approximately 40 degrees Fahrenheit. It is heated by flowing over pipes that contain hot antifreeze from the power plant next door. This allows the water's temperature to warm up, while the hot antifreeze cools down to be reused.
Filtering the Water
The water coming into the plant is salty seawater. There are several processes that the water goes through to be transformed into fresh, drinkable water. First, there is a trap for fish and other sea life that get into the pipes. The water then goes through a filter that eliminates microorganisms that are 5 microns or larger. One micron is the same as one-thousandth of a millimeter. That's pretty small!
Paul shows a filter that traps organisms 5 microns or larger.
The last filter that the water flows through filters out salt. Water moves through a tube and is then pushed outwards through layers of screens. The holes in the screens are so small that they trap the salt and let the water travel through. When the water comes out of the filter, it no longer has salt in it.
An example of the filter used to trap salt, cut open to show the layers.
Small paper-like filters and screens trap salt as water flows through them.
Pushing the Water
In order for the water to move through the tiny filters, it needs a lot of pressure. Engines move pistons, which create enough pressure to force the water through the small filters.
The water has to be under immense pressure to permeate the filters--50,000 psi!
For every 30 gallons of seawater that is brought in from McMurdo Sound, about 21 gallons of it is filtered into fresh water. The remaining water carries the filtered salt back to the sound.
Treating the Water
Once the water is filtered, chlorine is added to kill any germs. Since chlorine is acidic, it lowers the pH of the water. Soda ash, which is basic, is added to balance the pH of the water. The pH of pure water is 7 and most drinking water is between 6.5 and 8.5. The pH of the water at McMurdo is around 8.7, which isn't unhealthy, but which causes water to have a slight alkali taste to it. For example, it makes coffee taste bitter. This explains why people complain about the bad coffee in the cafeteria! The water's pH levels are constantly being monitored. Paul measures the pH level with two different instruments to make sure the readings are correct.
Instruments measure the amount of chlorine and the pH level of the water
McMurdo versus Iowa
Paul used to work at a water utility company in Iowa. He said they used to purchase chlorine by the ton to treat the water there. Here in McMurdo, they purchase it by the 10 gallon bucket. The reason he needs less chlorine here is because the water is far cleaner.
The chlorine tank ensures the drinking water at McMurdo is healthy.
Questions
Why does salt water freeze at a lower temperature than fresh water?
Paul said he needed to treat the water in Iowa with more chlorine than the water in McMurdo because McMurdo's water was so much cleaner. Why do you think Iowa's water was more polluted or contaminated than McMurdo's?
Math Connection
Paul was able to give us a tour of the water plant without worrying about his water tanks overflowing. Paul knows that it takes 5 minutes to fill an inch of water in the tank. Once the water level reaches 14.5 feet (marked by the penguin), he needs to shut off the tank. The picture below shows the water tank level when I arrived (find the small red mark in the tube). How much time did Paul have to give me a tour before he had to stop the water from flowing into the tank? (Hint: every line on the gauge is one inch).
The red marker in the tube shows the current water level in the water tank, while the penguin marks when the tank will be full.
Paul also has to keep his eye on the Chlorine tank. The tank fills at a rate of 6 gallons per hour. If the tank has 5 gallons in it when Paul begins his tour, how much time does he have until it reaches 10 gallons?
Cool Careers in Antarctica
Meet Paul Jones.
Meet Paul Jones. He is from Montezuma, Iowa and taught science for 36 years before retiring. His first experience in Antarctica was in 1997 when he came down as a teacher through the Teachers Experiencing Antarctica (TEA) program. TEA is the predecessor of the PolarTREC program that I am in! In 1998 he retired from teaching and spent time working for the utilities company in his town. He thought about working in Antarctica and in 2004 started working in the water plant facility. He has returned each year from November to January ever since.