In this post, I will share my experience using a flocculant to clarify and purify silty or muddy water while camping in the wild. I will explain how flocculation works, my experiment with it, and a step-by-step guide for using it on your next camping trip.
I spend a lot of time talking to customers about how they use their PYURIFI units. One of the first questions I get, especially from the River Rafting crowd, is “How does it do with silty water?” My answer isn’t one that I like giving: Like any filter-based water purification system, PYURIFI will become fouled faster when you use silty water. This means more frequent backflushing and a shorter lifespan for both the carbon and UF cartridges. So I’ve been on a bit of a quest to figure out a better way to solve this problem.
What is Flocculation?
A while ago I came across the notion of using a flocculant to help settle out the water faster. So I started Googling. While down this rabbit hole, I found this video on Youtube by some students at MIT. Flocculation It does a great job of explaining what’s happening in this process. Instead of me telling you what it says, take 5 minutes and check out their video, then come back and finish here… I’ll wait.
Image Credit: https://www.fluidra.com/projects/coagulation-in-water-treatment/
OK now that you’ve got the science check this out. I wanted to do my own experiment and see just how feasible this was for treating water while out in the wild. I went out to a local river, the Crooked River, which was running high and had lots of suspended solids. It is also a pretty cloudy river when it is running normally. I grabbed 4 gallons of water right out of the river and headed back to my makeshift lab.
My experiment with flocculation
After some more googling, I found that a solution of 1.5oz by weight of Alum dissolved in 1 qt of water would likely do the trick.
I also wanted to try the “just let the water settle” idea that I had come across during my research. I took one of the gallon bags of water and just let it sit. Then I filled a half-gallon flask with nasty Crooked River water, added 3 teaspoons of the alum solution, and stirred for 30 seconds. It occurred to me later that I should try the “more is better” approach and did one with 6 teaspoons of the solution too. I let these sit for 5 days and took some photos and made observations along the way.
Here is what I found
The water that I let sit on was still cloudy and looked like pretty strong tea. The water that I treated with Alum started to kind of get chunky and precipitate pretty much right away. It took a few minutes to see the results in the lower concentration flask but the one with 6 teaspoons started to look curdled right away. After 2 hours of settling the water was clear enough that I would consider filtering it and not feel bad about the filters doing extra duty.
On the fifth day, I filtered the higher concentration flask with a PYURIFI unit and drank some nice refreshing water.
I know what you are thinking. “I’m not going to wait 5 days to filter water out in the field!” Yeah me either, honestly I let it go that long because we went camping and I couldn’t get back to it sooner… But here is the scenario that I came up with for how this would go down on a backcountry trip. Keep in mind that this is for really murky water, normally you wouldn’t need to do this if the water is relatively clear.
How to use flocculation while camping to clarify and purify silty or muddy water
Step #1 - Make an Alum Solution Ahead of Time
Alum takes a while to dissolve. If you choose to just add alum crystals to your water, plan to stir for 5-10 minutes to get the crystals all dissolved. If you use the solution, you only stir for 30 seconds or so! I used McCormick Alum. It’s the same stuff that you would use for pickles or to grow crystals from in your kid's science experiments. I used the whole canister in one quart of water (1.9oz to 1 qt.).
Step #2 - Get a good collapsible bucket.
Step #3 - Fill that bucket and add some Alum!
Add 1.5 cups of the solution to the water. (If you brought the whole qt of solution you should have enough to clarify 16 gallons of water.) If you feel like you will need more water than that, you can double the concentration of your solution. Just remember that at double the concentration, it will take only half as much to treat the water.
Step #4 - Stir that water.
Use a spoon or stick to stir the water/alum solution for about 30 seconds. This is where the solution will save you time!
Step #5 - Wait... this is the exciting part!
Wait 1-2 hours or as long as you can afford to. This is where you get to do pretty much anything other than making water. Fishing, Napping, Cooking, Just sitting in your chair and enjoying a cold beverage... whatever you want!
Step #6 - Filter the Clarified Water
Your water is clarified but not purified until you filter it. The flocculation process will get all the big particles and even some of the biological contaminants out, the small stuff that will really get you is still there though! This is where a good filter that removes bacteria, cysts, and viruses is key to your kit. PYURIFI is clearly our favorite!
Here's how this would play out at Camp:
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Arrive at camp and first thing start the water clarifying.
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Then I would let it settle for at least 2 hours or until the next morning. You’re at camp! You can find something to do…
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The next morning purify enough water for some fresh coffee then more for the rest of the day before you break camp.
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Repeat at the next camp.
You don’t have to do this for all water! Just when it’s murky enough that you can’t see your feet when you are standing in about 6-8 inches of water. Any other time I would just purify straight from the water source.
So there you have it. 6 easy steps to clarify water that’s silty.
