Water Purification-Turbid Water

Whether your preferred way of "purifying" water, which really means sterilizing in most circumstances, is by way of filtration, or UV-light treatment or by chemical means, the quality of the input water will have a significant impact on the effectiveness of your preferred method. One of the important parameters is water turbidity, i.e. the presence of small suspended particles.

The impact on filtration is the most obvious: turbid water clogs your filter eventually. The impact on UV-light treatment might be less appreciated, but particles lead to scattering of light and that reduces the efficiency of the treatment. What is less appreciated is that microbes in general are harder to kill by whatever method when attached to particles, which affects the efficiency of light as well as chemical treatment.

While preparing for my Utah traverse I was looking for ways of dealing with fine suspended particles in crude source waters. On backpackinglight.com (https://backpackinglight.com/forums/topic/72551/) I stumbled on an article describing the use of "alum" (potassium aluminum sulfate) for just this purpose (David Thomas is the go to guy on that thread). Alum is a so-called "flocculant", a treatment that aggregates smaller particles to larger, filterable ones. Your local water authority likely uses this system if suspended solids in the feed water is a problem at the intake of its system. While I have outfitted my Sawyer Squeeze with a 20 micron Nylon screen to filter out small particles before they reach the fibers that do the ultrafiltration, Utah sand is too fine to be effectively captured by this screen. Therefore "better living through chemistry"! It's a professional deformity.

I carried a small dropper bottle with a solution of 16 g of alum in 20 mL of water. This translates into about 0.5 oz in 0.7 fl oz for you imperial people. This does not have to be exact. This is an almost saturated solution, so there may be some solid remaining at the bottom. Don't sweat this. When I had to deal with turbid water I added 5 drops/L, shook up the solution and let it stand for about 15 min.
Below a photo from treating water at the Dirty Devil, which looks like cement water.

The bottle on the left is treated water, the one on the right untreated water (settling time about 15 min). You can actually see the coagulated solids at the bottom of the  "treated" bottle.

I then simply decanted the alum-treated water through a 1 micron sump pump sock (amazon) into a different bottle at which point the water was basically clear and ready for filtration or chemical treatment or UV-light treatment, if that is how you roll. The yield is about 0.8, meaning one liter of alum-treated water will yield about 0.8 L of sterilizable crude water. This is conservative, I just did not have many opportunities on that hike to clean the filter sock at a water tap. If you transfer more of the alum-treated water to the pump sock, more of the aggregated solids will come over as well and clog the cloth of the sock, reducing the flow rate over time.

Regardless of how low the quality of the input water was, I always obtained a clear feed for the sterilization. Worked like a charm! The "fraction of an oz counters" may be concerned about the weight of the sump pump sock. The bulk of the weight is a metal ring sown into the rim of the sock. If you liberate it and replace it with a zip tie to give the sock some stiffness, your pump sock will well weigh next to nothing.

Redundancy in your personal hiker geographic information system

In 2017, crossing the Pyrenees on the Haute Route des Pyrenees, instead of carrying my printed maps for the entire journey with me the entire time, I opted to mail stashes of maps to myself in my food parcels. What could go wrong? Everything! A "stupid light" decision as Andrew Skurka would call it.

With the exception of one parcel that I received in Gavarnie, I could not collect any of the other parcels. It turns out the transfer of parcels from the German postal system to the French and Spanish one is not frictionless. An additional problem being that both the French and Spanish postal systems only hold General Delivery parcels for two weeks, and, in some cases, not necessarily exactly two weeks either. The "no food" part was not so bad, you can always cobble something together, but having no printed maps was no fun. At all.

By looking at larger scale maps posted in refuges whenever I could put a walking route together to the next refuge, but I also got lost badly once because I misremembered an important detail. Instead of getting off the Table des Trois Roix and heading to a stone shelter, I ended up walking around the mountain. By the time dead reckoning suggested that something was amiss night was falling. Not making the intended destination is not so bad. However, the area around the Table des Trois Roix is a karst area (limestone) and there was no water to be found for a day and a night. No food and nothing to drink. Not fun.

After I had found my way again a very nice Frenchman who gave me a ride let me have an old copy of a map of the area he kept in his car. This covered at least part of the next section and then I was lucky enough to meet again a Frenchman whom I first had met in La Pierre St. Martin at the refuge. He let me tag along with him to Gavarnie, where our ways separated and I received my maps and food as planned.

The following year, continuing the HRP, I decided to carry a phone with maps on it (Gaia GPS) and printed maps as a backup. I have a hard time lining up the big topological features in the landscape with the maps shown on the small phone screen, I do much better with printed sheets (11 x 17) of the same maps. I can't see myself hiking a trail, let alone a route, with just a map displayed on my phone and no larger scale image to look at.

The phone died at some point, but I had my printed maps and I was ok for most of the journey with the exception of one spot where a sort of optical illusion let me not appreciate the fact that what looked like a solid rock wall was in fact a set of two rockwalls with a gully in between. This gully was what I needed to walk up. In this situation having a working GPS would have allowed me to determine that I was maybe 100 m off from where I had estimated to be on the paper map. As a result I walked down the wrong watershed, which also featured a lake down below just as the watershed I should have gotten into. I had all reason to think I was going down the right trail. But I was not. This cost me a day as I only reluctantly returned to the pass from which I had come down, thinking that no new information would transpire if I did return and that I was likely missing something else. Eventually I returned to the pass since I could not convince myself that I had identified what else I was missing. Sitting up at the pass again and scratching my head as to what I needed to do, a change in light made it suddenly obvious that I was not staring at one wall, but at two stacked walls. Heading over there I found the narrow gully and I was off to the races.

During my Utah traverse I drowned and destroyed my phone while recharging it. But I carried printed backup maps. Then one day I needed to find a water source that I had confirmed with a ranger was running and that was shown on the map. However, this source was located deep in a canyon and I was not able to triangulate using the compass to larger features in the landscape as these were hidden behind the very close horizon of the canyon rim. For the Utah trip I had purchased an Inreach mini to give my home crew a GPS location every night so that they could monitor my progress and see that everything was ok. So I pulled out the Inreach mini and found out to my horror that the default way to display coordinates was the DDM format (degrees, decimal minutes) while my maps were printed using a UTM grid! There are online resources for the interconversion of the formats, but that's no help in the backcountry, whether your phone is alive or dead.

I had purchased the Inreach two days before I started my hike because you can't buy these things or have them shipped to where I live because nothing containing a lithium ion battery can go into the cargo hold of an airplane. So I was not really familiar with the Inreach, I had barely managed to get it set up for what I wanted to use it for. I had downloaded the user manual to my phone, but that was on the Fritz, so I was up the creek sans paddle.

So what do we learn from Thomas' misadventures?

1. Have printed maps and carry them with you, do not mail them to yourself, particularly when using unfamiliar postal systems. In the US mailing them to yourself, or, better, have someone mail them to you via the USPS as you progress along the route is not as big of a risk. USPS has a long hold time for General Delivery mail and you can check online whether the item has arrived at its intended destination.

2. Watch your phone like a hawk if you use it as your GPS on a hike. The combination of electronic maps and paper backup is much more powerful than either alone, even if the maps were generated by the same software.

3. Make sure that the way coordinates are displayed (UTM, DMM, DMS) on your Inreach or similar device is the same as the grid on your printed maps. If your phone GPS fails, for whatever reason, your Inreach can provide some of the function of the phone to get you located.

4. As I write this I find out that there are actually apps that you can have on your phone that will do the interconversion without requiring access to the internet. For example: Lat/Long & UTM Converter for Android or Coordinates-GPS Formatter on the Apple App store. I have not checked out either, but having something like this on your device is an easy way to increase redundancy in the way you access geographic information while in the backcountry.