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.