Only if there was something to mix with the water to take away the shock of the RO plant cost.
There however are handheld and operated RO pumps which can be bought, but these are quite expensive to buy and maintain and still not small enough to be travel companion.
Having travelled lot, I wouldn’t rely on basic purification say using tablets or UV to think water is fit for consumption. Possibly these purification techniques are okay if one is in the upper catchment or a reasonably undeveloped area (e.g. national park or high altitude) and needs a drink. Then in such cases, basic treating of spring or stream water which looks okay to drink would still be advisable to remove any microbe infections from animals/wildlife.
They possibly have a purpose where one doesn’t fully trust the local treated tap water, even though the locals drink it. The purification techniques would provide a final treatment process to remove any lingering microbes which the locals may have built up some resistance to.
In my travels water which contain a lot of things which may not be obvious to the naked eye and would remain in the water after these simple purification techniques. A recent example as I alluded to above was in the Atacama Desert where some of the natural water sources are very high in copper and other minerals…so much so that tiles in showers are stained a green-blue. The water coming out of the tap looks fine, but if one didn’t know and used one of the purification techniques, they would still be consuming water very high in copper and minerals. Drinking high copper water can have acute affects on the body. Our host in San Pedro de Atacama warned us not to drink the water as a result (and confirmed independent information we had received elsewhere).
Chemicals such as pesticides or other inorganic compounds can dissolve in water or can bind to clay in water. The water may look relatively clean but again purification won’t remove such compounds.
Also, while a UV or tablet treatment may have an effect on disinfecting the water, any toxins resulting from these microbes may still be there…an example is blue-green algae.
If anyone is interested in reading some general information on UV treatment, information can be found here.
