Saturday, October 11, 2008

Making Water

Antarctica is a land mass with huge amounts of ice upon it. In some places the ice is reported to be almost 3 miles thick. You would think that with all that frozen water, getting some to drink would be a simple matter of melting it. Not so fast. It takes huge amounts of energy to melt ice when it is minus 30 degrees F outside and the sun is absent 4 months a year.

All the water for McMurdo Station and Scott Base is produced in the McMurdo Water Plant. I had the opportunity to visit the plant. A sketch of the basic process is shown.


The basic idea is that there is a long pipe going from McMurdo base into the Ross Sea, the liquid part, deep underneath the frozen top of the sea. The sea water enters the plant at about 28 degrees F. If it isn't warmed, it will freeze the equipment. So, the cold sea water runs through heat exchangers (which recover heat from the diesel power generators).
The heat exchangers warm the incoming sea water from 28ºF to approximately 37ºF. The warmed sea water then is stored, indoors, in a huge steel tank. Sea water is very corrosive to steel. Therefore, this enormous tank has a plastic liner to keep the sea water from coming in contact with the steel tank walls. In this sea water there are all manner of tiny and microscopic organisms that must be filtered out before drinking water can be made.


The sea water is passed through a series of filters, each finer than the one before, to remove all microsopic organisms and debris. After filtration, the sea water is forced under very high pressure through the reverse osmosis tubes (shown at right). These RO tubes allow water to pass through a semi-permeable membrane while salts and other chemicals remain. The sea water is passed through this system two times to extract every possible ounce of pure water. There are two sets of these RO tubes. The second set of RO tubes, not pictured, are just to the right of the photo.


After all the pure water is extracted from sea water, the remaining brine is returned to the sea. The pure water is treated with carbon dioxide (CO2), calcium carbonate, and chlorine. These give the water desirable properties for drinking, protect the pipes, and prevent the growth of bacteria and other organisms in the drinking water. Water ready to drink is stored in huge steel tanks, indoors of course, and is pumped out to the McMurdo Station and Scott Base.

I mentioned earlier that excess heat from diesel power generators are used to warm incoming sea water. There is still more excess heat from those generators that is used to heat a recirculating glycol system that is used to heat some dorms (including mine) and buildings on station. Currently there are the old and new power plants. The glycol heat exchangers come from the new power plant which uses more efficient generators. The old power plant is scheduled to be replaced by the new one when the new plant gets all the generators installed and is fully operational.




There is a sophisticated computer-driven monitoring system for the power plant. It may look like a video game but it is monitoring the function and condition of the six generators that are our lifeline. The temperature, oil pressure, engine RPM, electrical generation and other parameters of each of the six generators are displayed for the operator to see. Tests on any specific generator can be conducted. Logs of electricity production requirements along with fuel consumption are kept.


I hope you have enjoyed this tour of McMurdo's power and water plants. I have just completed a tour of the wastewater treatment facility and it too is quite interesting. The biosolids are shipped off continent to a US landfill; the treated liquid is returned to the sea. In a way, we are a closed loop liquid system. We make purified water from the sea and return the treated water to the sea.

7 comments:

Ms. Adams said...

Just found this blog! Great information! I'm going to share it with my 7th grade students in my science classes. Thanks for providing the detail and perspective of living there.

Our 8th grade science teacher leaves tomorrow (Oct.13) for Antarctica. She will be in the Dry Valleys for about 5 weeks. Wonder if your paths will cross at McMurdo.

FYI - her web page is http://www.ryejrhigh.org/ellwood

Sheila Adams, Rye, NH

asthepumpturns said...

The first part of the water treatment process is also how dialysis water is made. Very cool!

Anonymous said...

Hello! We are so glad to see that you are enjoying yourself and that you are well. We think of you often and look forward to your return (and hearing all of the many stories that you are storing up)! We will be monitoring your blog and praying for a safe adventure.
Fondly,
Caryn and the Surgery Center OR Staff

Sarah said...

I'm enjoying reading your posts about the Arctic life, it sounds like you are having fun! I was shown this clip a few days ago and thought you might enjoy it, though I don't know if you'll be able to view it. http://sendables.jibjab.com/sendables/1191/time_for_some_campaignin#/teaser/1191


Sarah Keefer...it's still weird to write Keefer instead of Roehrich.

Jessica said...

Thank you for the bookmarks! I got the bookmark with the nacreous clouds on it. Mrs. Shuwarger will be sending you something from our class. Hope you have a happy halloween!!!!!!


Mrs. Shuwarger's student,
Jessica Pascadlo

NRH said...

Hey Dr Shuwarger!
Thanks for the the bookmarks! I love by "Penguin Power!" one! It's being put to a great use!
-NRH

Ray Wetwater said...

Hi from Tucson Arizona in the USA in Calif. San Deigo out to sea about 3 miles I think. The WasteWater Treatment plant dumps it's solids using a underwater pipeline. You guessed where all the big fish hang out at. Right! And it's not illegal to eat the fish you catch there. Thou I wouldn't want to know that. As you might know Calif. rules about making things safe are many times stronger than the EPA. I know the people in Antarctica are many times smarter than the people in Calif. and besides that they have the US Airforce to pay for anything that to me or you might seem foolish.