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Tuesday, August 13, 2013

Water, treatment, and desalination

I am a big fan of Sawyer water filters. I used the older sawyer two bag, four liter system in Alaska - in conjunction with Aqua Mira. It works beautifully, you don't have to buy replacement filter cartridges, it is a great system. Probably my only complaint is that it doesn't get out odors or flavors - because it is of hollow fiber design - and while it has never been a problem it is the sort of thing that sticks in the back of my mind. I don't understand why there isn't a small carbon device that the water runs through after exiting the filter. It is the sort of simple thing that they could sell millions of.

we also used Aqua Mira, in part because both of us were NOLS instructors and NOLS uses Aqua Mira. It is a great product, it is a two part chemical treatment that you add to a liter of water and 30 minutes later you have treated water. We would see fresh water spilling into the ocean and paddle up to it and fill a dromedary without getting out of the cockpit of the kayak, treat it and then keep paddling. Then, hours later we would arrive at our beach and have drinkable water.

I have talked about it before but I am a die hard user of MSR dromedaries. I have a ten liter and a four liter - so if I am using both I can carry 3.5 gallons of water, which is a lot. They are versatile, and durable and not that expensive. They tend to live in the cockpit in front of my feet, so they are usually easy to get to, but also out of the way. Being only 5'8" I have probably close to 18 inches in front of my feet, before the bulkhead.

In the past I have had PFD's with integrated hydration, and you know what? they never work well. They add a lot of weight to your PFD, and they are never big enough. On the inside passage I used a 1.8 liter integrated reservoir in my Astral 300r. I think I refilled it twice and then stopped using it. It was hard to fill, and way too small for a full scale expedition - where you are spending all day in a boat. I am sure it would be great on day paddles. I have already decided how I am going to do water on my next trip, I am going to keep it simple with a Camelbak Unbottle. An insulated 100 ounce bag will sit under the bungies behind my cockpit. When in doubt keep it simple.

My next filter will be the Sawyer Squeeze. You fill a bag with water, attach it to the filter and squeeze. It is surprisingly easy. The hardest aspect is actually filling the bag - if you are sitting in a kayak and hold the bag under water, it will only fill about half way. I am guessing that exterior pressure on the bag keeps it from filling, someone correct me on the physics please.

Sawyer has made a number of filters designed to be dipped in the water and used directly, or you fill a bag with water, or a water bottle with water, and draw water through the filter with your mouth, which got me thinking. Why can't they make a filter that removes salt from water? Why can't I dip a bottle in the ocean, and draw water through a filter and have clean, fresh non-salt water? There are a handful of pump - okay I can find 2, and they are expensive, slow and bulky - filters that work as desalinators, but beyond that you are either looking at evaporation systems or other high priced, heat based systems. There is nothing small, portable, simple, reliable and inexpensive. And let's face it, that is what people want from a filter.

The problem comes down to size. The sawyer squeeze filters down to .1 micron, which is pretty small. Small enough to get Giardia and Cryptosporidium. It turns out that Sea Salt is .035 microns in size, so significantly smaller than the squeezes .1. But Sawyer also makes a filter that will get out viruses, which removes anything .02 or smaller. In theory that is smaller than sea salt, so why doesn't it work? The answer is, I don't know, but I want it to. I want to fill a ten liter dromedary when I get to the beach with salt water. Hang it from a tree, connect a filter to it and have water feed via gravity to a 'clean' bag. When I plan an expedition my two big concerns are campsites - can I get off the water? - and fresh water. This would solve that big concern.

19 comments:

  1. Re: mechanical filtration of salt from saltwater. I think you are mistaken. Once sodium chloride dissolves in water it becomes much smaller than its crystallized form and separates into sodium and chloride ions. These would be impossible (I think) to filter mechanically. Someone tell me if I'm wrong.

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  2. I could totally be wrong. I found on wikipedia a listing of various items and their sizes in microns which is where I got the numbers from, and it listed 'sea salt' that may not be 'salt dissolved in water'. There are definitely two Katadyn hand operated desalination pumps. But they are very slow. http://www.katadyn.com/usen/katadyn-products/products/katadynshopconnect/katadyn-desalinators/

    Thanks for the comment.

    PO

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  3. My informal web searching shows a sodium ion to be 116 picometers in size or 0.000116 microns. Smaller, I'd bet than the H2O molecule. That's why I think mechanical filtration is out. Probably there's a better chemistry explanation.

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  4. Check this out.

    http://nadgeekayaks.com.au/news-events/news-item/article/water-water-everywhere-nor-any-drop-to-drink.html

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  5. if it is so small, and I have no doubt it is, I wonder how the katadyn product works. When I first thought of this blogpost I did a search and found that site with the home made desalinator. very interesting.

    PO

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  6. This is interesting discussion. Reverse osmosis membranes rejects most salts, but allow pure water to pass through. The problem is, you need to exceed the osmotic pressure to allow water pass through the RO membrane. For sea water like Pacific Ocean with total dissolved solids of 33,000 mg/L, the osmotic pressure will be about 350 psi. Allow another 300 psig to overcome mechanical losses, so you are looking at 650 psi. You can generate this pressure using hand pump and may recover 10-15% water.

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  7. Interesting post...Here in Canada, we use www.sapphire-water.ca. They have great filtration and purification systems. Sawyer water systems also sound interesting I will have to check it out. Thanks for the post.

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  8. Mark, do they make something suitable for kayaking? I didn't see anything on their website.

    PO

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  9. Important post. People who fall ill from waterborne diseases can't work. Women and girls who travel hours to fetch clean water for their families can't go to school or hold on to a job. Without proper sanitation, human waste pollutes waterways and wildlife habitat. Global warming and population pressures are drying up water supplies and instigating conflict over scarce resources. Expanding access to clean water and sanitation will have ripple effects throughout local economies and societies.
    @ LINA

    ReplyDelete
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  11. Water filtration is the process of purifying water in order to remove unwanted solids, microorganisms, gases and chemical substances. The water is passed through a medium which retains the solids and allows only water to pass through. It is important that one gets clean, purified water to avoid waterborne diseases. There are various types of water filtration. They include; ion exchange, distillation, filtration, ultra-filtration and reverse osmosis. more

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  12. One of the cheaper filters out there, but also one of the more best water filters, is the PUR CR-6000 two stage pitcher, and this one is only a refrigerator filter, and therefore it sells for just seventeen bucks, but nevertheless, is still very effective at improving your water quality. This one is actually the most recommended water filter out of any on the market. find out more

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  13. They tend to live in the cockpit in front of my feet, so they are usually easy to get to, but also out of the way. Being only 5'8" I have probably close to 18 inches in front of my feet, before the bulkhead. my site

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  14. لدينا مميزات في خدمات كشف تسربات التي تقدمها شركة ركن البيت التي تكون متخصصة فيها فتعاملك مع شركة كشف تسربات المياه بالدمام لديها امكانيات جيدة يساعدك علي التخلص من مشاكل التسريب التي توجد لديك بسهولة دون التعرض للخطر حيث نمتلك في شركة كشف تسربات بالدمام الامكانيات والفنين المتميزين الذين يقدمون الخدمة بتميز فاذا كنت فى حيرة من امر التسريب الذي يوجد لديك فعليك ان تعلم ان خدماتنا منتشرة في جميع انحاء المملكة مثل خدمات شركة كشف تسربات المياه بالرياض التي تحل لك المشاكل المتكررة المتعلقة بالتسربات فلا داعى للقلق من الان لانك سوف تملك فني جيد منزلك يحل لك كل مشاكل التسربات و كيفية القيام بهذه الخدمة وتذكر ان الحل الامثل فى شركة كشف تسربات بالرياض ان توفر كل الامكانيات التى تساعدك علي حل مشكلاتك

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  15. Saltwater purification is one of the more interesting backpacking activities because it utilizes the powers and wonders of nature to convert saltwater to fresh potable water that will definitely save you from dehydration. Want to learn more? Check this out: http://backpackingmastery.com/skills/how-to-purify-salt-water.html

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  16. There are microbes and other impurities in the water we drink. For the most part, the impurities are harmless. If it wasn't, the government wouldn't allow us to drink it. penapis air

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  17. I've read about how must nations in the Middle East have come a long way in their desalination process of turning sea water potable and fit to drink. That's why I read a lot about the technology and was browsing through a lot of material online and saw a DIY way of purifying salt water. Awesome! See it here and be amazed how easy the process is: http://myoutdoorslife.com/diy/how-to-purify-salt-water.html

    ReplyDelete