The application of a reverse osmosis system that most people are familiar with is water purification, for domestic, municipal, industrial, and medical use.
The technology of reverse osmosis involves forcing a solution against a membrane that filters out large molecules and particles, allowing the solvent (usually water) to pass through.
The system is effective up to a point, with both advantages and disadvantages.
Osmosis is the natural process by which a solution will achieve a uniform dispersal of dissolved matter throughout the solvent.
The movement of molecules through the solution is called osmosis; reverse osmosis is achieved by exerting pressure to force the solvent through a membrane with pores too small to allow the dissolved particles to pass.
First used to 'purify' sea water and later to filter fresh water as well, reverse osmosis (RO) is now used in many processes, including concentrating fruit juice and maple syrup, producing fine wine, getting water out of ethanol fuel, and providing a spot-free rinse at car washes.
There are counter-top units to provide drinking water at home, portable units for hikers and also for army battalions, and systems able to provide enough potable water for a city.
The current systems vary in complexity, but consist of stages, or steps, in the purification of solvents, most often water.
First there will be at least one sediment filter to trap large particles that otherwise would clog the pores of the membrane.
After one or two preliminary filtering stages, the water passes through an activated carbon filter, and then is forced against the membrane.
After passing through the membrane, the water may again go through charcoal, and finally may be further sanitized by treatment with chlorine or ultra-violet light.
Systems may have as few as three or as many as six stages.
Although reverse osmosis is hyper-filtration, capable of removing most chemical and even nuclear pollutants, it is not 100% reliable against bacteria, especially since the membranes may develop leaks or become otherwise compromised.
To be safe in using this system at home, start with water treated for bacteria, using the system to filter out chlorine and other contaminants that may be present.
The initial purchase and installation costs may be quite high, and the system must be serviced regularly.
If a whole-house system is used, there is much wasted water to be disposed of, stressing septic systems and raising water costs.
The RO system will reclaim no more than 30% of the water that passes through it, and the rest of the water will have concentrated amounts of pollutants.
Another factor which should be considered is that RO removes healthful minerals as well as other particles.
There is also the problem of maintaining the system in perfect working order.
Replacing the filters and the membrane must be scrupulously done on schedule, and there should be a way to monitor the system for leaks.
Periodic water tests can help to ensure that the system is providing clean water.
A reverse osmosis system can have useful applications in the home and in other areas, but the complexities of the process must be understood, and the quality of its performance monitored.