Ice and Medicine at the end of the earth

49. Where do you get your drinking water? Do you melt ice?


As you can imaging, McMurdo (town) and WAIS Divide (Deep field camp) get their water in different ways. 

T.J. wrote:

At WAIS Divide all the water we have is melted from snow. In the galley and wash area, there are two big snow melters which are connected to cisterns. The melters are electric and get power from the two generators which supply power to the entire camp. A fun fact: it takes as much energy to turn ice to water as it takes to boil water that starts at room temperature (The latent heat of fusion is ~80 calories for ice. The definition of a calorie is the energy requires to raise the temperature of water one degree Celsius. So if room temperature is 20 degrees C (~70 degrees F) then is takes ~80 calories of energy to boil a gram of water). In other words, it takes a lot of energy to make our drinking water.

So, how do we do it at McMurdo?  We need a much large supply of water at McMurdo, so we have a desalination plant on base.  We take the salty, dirty ocean water and turn it into clean, fresh drinking water!  It makes around 60,000 gallons of potable water per day.  Now that is a lot of water!!

The first step of desalination is to heat the water to 37 degrees Fahrenheit.  The water is then pushed through a 25 micron and 5 micron filter to remove any particles.  The water is then pressurized from 40 psi to 700 psi whic helps with reverse osmosis.  The pressure pushes the water through membranes — the salty water stays on one side and the clean unsalted water moves throught he membrane into water pipes.  Chemicals (Chlorine and Calcium carbonate) are added to the water to make it safe for drinking.

The system makes 1 gallon of fresh water for every 3 gallons of salt water pumped into the system. 

Now, what do we do with all the salt water?  It mixes with the cleaned waste water (see waste plant post) to form the perfect salt mixture before it is released back into McMurdo Sound.

Hopefully I will tour the desalination plant soon and post photos.

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