The osmosis process was first discovered in 1748 by a  French physicist Jean Antoine Nollet who observed water diffuse spontaneously through a pig bladder.  Osmosis is the natural tendency for water to spontaneously pass through a semi-permeable membrane separating two solutions of different concentrations (strengths).  The water will naturally pass from the weaker (less concentrated) solution containing fewer particles of dissolved substance to the stronger (more concentrated) solution containing more particles of a dissolved substance.  Thus, natural osmosis causes the stronger solution to become more diluted and tends to equalize the strength of the solutions on both sides of the membrane.

Two centuries after Nollet’s discovery, RO (reverse osmosis) was still not much more than a laboratory phenomenon until a Thayer student project.  The Thayer student project helped create a new multi-million dollar RO industry. Dean Spatz ’66 Th’67 arrived at Dartmouth, commercial applications for reverse osmosis systems were in their infancy. In ES 21: “Introduction to Engineering,” Spatz and Chris Miller ’66 Th’67 were given a jar of brackish water and told to find a way to make it potable. The pair came up with a prototype for an RO purification system. They ramped up their undergraduate project into graduate-level research that eventually led to Spatz winning contracts from the Department of the Interior to develop low-pressure reverse osmosis systems. Spatz also thought up new applications for the emerging technology. Shortly after getting his degree from Thayer, for example, he built a reverse osmosis system for a friend’s maple sugar operation to separate the maple sugar from the sap. In 1969 Spatz co-founded an RO company, Osmonics, with longtime Thayer Overseer Ralph E. Crump

How Reverse Osmosis works:


Reverse Osmosis, also known in some places as hyper filtration was first developed over 52 years ago with the successful development of a semi-permeable membrane. The semi-permeable membrane can selectively extract water “molecules” from the water while keeping the contaminants away from the permeate side (I. e. the clean side of the membrane).  In the early 70s, the first commercial low pressure semi-permeable membrane was developed and is capable of producing 1 to 5 gallons per day of clean, safe drinking water.  Today, with technology advancements, the capacity of such low pressure household system can provide up to 100 gallons per day or more, that is more than enough to satisfy all the drinking and cooking needs of a family. In many places and cities, the local water authorities invested heavily into this technology for municipal water recycling programs due to increasingly questionable natural water sources,  This technology has proven itself to be well developed and reliable.

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