I just thought people would find this interesting:
Within the Ukraine lives the Hutsul people. They are masters of a specific type of wool blanket technique called “lizhnyk,” which is made from Carpathian sheep wool.
Creating the blankets is a long and difficult craft, but the results are beautiful.
One of the most ingenious parts of their craft involves help from the river. A valylo is a river-powered wooden washing machine; which will beat the blankets until they are soft and lose their sheep-smell.
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Thought to be a system over 100 years old, the valtoare/vâltori (whirlpool) in Romania works by channeling water into a large wooden funnel-like barrel. The funnel has gaps wide enough for water to flow out, but not wide enough for the cloth to slip through.
The force and angle of the water hitting the wood creates a spiral of water, which tumbles the clothes thrown inside.
Historically, people would rent the usage of these from the owner, with money, grain, or by working the land for however long it took the clothes to wash. Today, they are free.
“Today, whirlpools remain popular, especially among people from rural areas. They are used for washing wool fabrics free of charge, but people still like to contribute a small fee to the budget for repair and maintenance.” Peasant Art Craft
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But how do you sanitize the water?
If you're literally just using raw, untreated river water, your clothes aren't getting clean.
Water is a great solvent and with agitation for hours with no labor would clean great. Soap just makes it faster. The deepest cleaning methods are abrasive and approach sanding/polishing, like brushes or steel wool or scratchy sponges, and those methods and a rinse will remove anything over time, including the object you're cleaning. All batch clothes washing uses the fabric rubbing against the rest for friction.
When you dry in the sun, the UV helps with disinfection, not that the idea that sterility is necessary for blankets holds any validity.
With a mountain stream fed by springs or snowmelt, I'd trust that to rinse sweat and dirt out of clothes or blankets well enough. If you're making surgical dressings or something, yeah, sterilize them separately.
Edit: plus, there may very well be a basin nearby you can use to suds up the fabric (ideally with something less damaging to waterways than most laundry soaps)