The relationship between humanity and water has never been just about survival—it has always mirrored the progress of civilization and technology. In pursuit of safe, usable freshwater, we invented sedimentation, filtration, and distillation. Each breakthrough profoundly reshaped how humans obtain and use water resources. Today, reverse osmosis (RO) membrane technology has become central to global water resource management, widely applied in seawater desalination, industrial reuse, and household drinking water.
Yet, no mature technology emerges overnight. The history of RO is a scientific and engineering journey spanning three centuries: from the discovery of natural phenomena, to the establishment of theories, and finally to the development of synthetic materials and industrial applications.
The “History of RO Development” series will follow this historical trajectory, exploring the evolution and breakthroughs of membrane science—tracing how reverse osmosis grew from its initial spark into a long quest that ultimately made it one of the key technologies supporting global water use today.
This first chapter takes us back to 1748, when it all began with the unlikely use of a pig’s bladder.
The Origin of RO Membranes: A Laboratory in 1748
In 1748, French physicist Jean-Antoine (Abbé) Nollet carried out a seemingly simple demonstration. He sealed a small flask of an alcoholic solution (likely wine/ethanol) with a fresh pig’s bladder and immersed the flask in a container of water. Hours later, the membrane stretched and swelled; when punctured, the liquid inside burst out like a fountain. This revealed that the solvent (water) could pass through the membrane, while the solute (alcohol) was retained. It was the first systematic record of the natural phenomenon we now call “osmosis.”
In modern terms, Nollet’s experiment highlighted two critical principles:
Semipermeability: certain membranes selectively allow solvent molecules to pass through while blocking solute molecules.
Concentration gradient: water moves from the side of lower solute concentration to the side of higher solute concentration, until equilibrium is reached or an opposing force is applied.
Although Nollet did not yet conceive of “osmotic pressure” or formalize a theory of semipermeable membranes, his experiment provided reproducible, first-hand scientific evidence. No one at the time could have foreseen that this discovery would lay the physical and chemical foundation of membrane separation, eventually becoming central to freshwater supply and water treatment technologies.
Osmotic Pressure: From Natural Phenomenon to Quantified Science
Nollet’s observations made scientists aware that certain natural membranes had the unique ability to “let water pass while blocking impurities.” But this was only a beginning. By the 19th century, researchers pushed this phenomenon toward theory and quantification:
1854 – Scottish chemist Thomas Graham formally introduced the term osmose, bringing the concept into academic discourse.
1877 – German botanist Wilhelm Pfeffer, through apparatus experiments, demonstrated that when water passes through a semipermeable membrane into a solution, it generates pressure. He was the first to measure and define osmotic pressure.
The recognition of osmotic pressure marked a pivotal turning point in membrane science. It transformed the question of “why does water flow?” from a qualitative observation into a measurable, calculable physical principle.
From Nollet’s experiment to the establishment of osmotic pressure theory, humanity gradually uncovered the secrets of membrane separation. Osmosis and osmotic pressure became foundational concepts in biology and physical chemistry, while also providing the theoretical stage for the eventual development of reverse osmosis. But moving from “seeing the phenomenon,” to “grasping the principle,” and finally to “realizing practical applications,” would still be a long road ahead.
In the chapters to come, we will continue along this three-century scientific journey, tracing how successive breakthroughs in theory and engineering gradually transformed reverse osmosis from a laboratory curiosity into a technology that reshaped the way humanity accesses and uses water.