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  • Writer's pictureCliff Jacobson


Green River, Utah

Eastern and midwestern waterways are generally clear and inviting. Not so in the far west. Desert rivers like the Colorado, Green and Missouri are brown-colored and too silty to drink. Visibility is measured in centimeters. The water, which looks like chocolate malt, has a murky, raspy taste. You won’t want to drink it even if it’s technically potable. What to do?

If you try to filter out the silt, your filter will quickly clog. Some people tie a piece of nylon hose over the intake hose of their filter; others rely on a commercial pre-filter of some sort. But the silt is so fine, and there’s so much of it, that nothing works very well for very long. For this reason, most people just buy water in plastic jugs and carry it in their boat. But at roughly eight pounds per gallon, the weight adds up quickly. A lighter solution is to use alum or liquid Chitosan to settle the silt, then purify the clear water with chemicals or a filter, or my favorite, the SteriPen™. Alum is used in home pickling to add crispness, and as a settling agent in water treatment plants. It is non-toxic and tasteless. Most pharmacies have it. A twelve ounce (340 gram) bottle contains enough alum to settle about 48 gallons of silty water. Liquid Chitosan, a derivative of chitin (it’s made from the shells of crustaceans) is another option. Chitosan binds with heavy metals, hydrocarbons, and suspended particles in water treatment. It’s used to clarify the water in swimming pools, beer and wine and more. The product is non-toxic, completely natural and 100 percent biodegradable. It’s manufacturer, Tidal Vision ( has a wealth of information about Chitosan on their web-site.


Fill your bucket with the silty water.

  1. Add about a teaspoon (the measurement isn’t critical) of alum or one per cent liquid Chitosan to one gallon of water. Use less Chitosan if the concentration is higher, more if it’s lower. A tablespoon of either is usually enough to settle a three gallon pail of silty water.

  2. Use a long stick to very slowly stir the water. Stir in ONE DIRECTION only. Continue stirring until a “flocculant precipitate” (it looks like snow) forms on the surface of the water—it takes about five minutes.

  3. When you see the snow-colored precipitate, STOP stirring. Allow the water to settle for about 20 minutes. At the end of this time the water will be clear and all suspended matter will have settled to the bottom.

  4. Use a Sierra cup or ladle to gently dip the clear effluent from the top of the bucket. Do not disrupt the sediment on the bottom with the ladle—doing so will cause the sediment to re-suspend.

  5. You can now boil, filter or chemically treat the clear water to make it potable. I’ve used this method to remove silt from river water on the Green River (Utah) , Rio Grande (Texas), San Juan (Utah) and Little Missouri (North Dakota) Rivers. It works great!

Above: Alum/Chitosan added. Stir SLOWLY in one direction only.

Bucket at far right shows clear (settled) water on top. Be careful not to disturb the sediment on the bottom when you ladle the clear water.

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