Much of man’s technological innovations today have been borrowed mostly from nature. One of them is a very important process called “reverse osmosis”. It is the opposite of the natural process called osmosis. What, then, is reverse osmosis and what does it do?
As man moves towards progress, water and the other natural resources of the world have become polluted and unsafe for use. Reverse osmosis is one of today’s important methods for processing water to make it clean and safe for use.
Osmosis and reverse osmosis
First, what is osmosis? Osmosis is a natural process where water of different concentrations and separated by a semi-permeable membrane will cause the water from the diluted solution to move into the more concentrated solution.
This is because this semi-permeable membrane (the osmotic membrane) allows only water to pass through and restricts most other elements.
In reverse osmosis, the opposite happens. Applying pressure, water from the more concentrated solution is forced out through the membrane into another container, in effect straining it from impurities. This is the process commonly used today to purify water.
The basis of the whole system is the semi-permeable membrane that acts as a strainer. This membrane is permeable only to water molecules. As the concentrated water (water with dissolved and solid particles of minerals, salts, etc.) is forced through the membrane, only water molecules can pass through the pores.
The most common artificial membranes used today are made from cellulose acetate, cellulose triacetate or aromatic polyamide resins. These are tough to withstand the high water pressures and can last for about two or three years before replacement.
These impurities that cannot pass through the membrane are composed of various mineral salts, heavy metals, other matter particulates, organic molecules, some bacteria, and even some viruses. These are rejected by the membrane based on their molecular or atomic weights.
The membrane removes these salts and other dissolved mineral elements, as well as other impurities like sugar, proteins, dyes, nitrates, and pesticides. All things considered, this improves the taste, color and other natural properties of water.
The process is also known to remove particles as small as ions or charged atoms. Today, it is also used to purify other fluids such as ethanol and glycol which passes through a membrane that rejects other ions and contaminants from passing through.
The most common force used in the procedure is pressure from pumps. The higher the pressure, the bigger the driving force.
In the old mechanical filter systems such as the standard carbon filtration, total dissolved solids (called TDS) cannot be removed. High concentration of TDS usually gives the water an objectionable taste, causes scale buildup in utensils and equipments, and causes poor quality in beverages and ice-making.
According to studies, reverse osmosis removes 95% to 99% of the total dissolved solids in contaminated water. Right now, it is considered one of the best technologies in producing clean water free from TDS and other contaminants and is therefore safe for human consumption.
There are some problems, of course, that must be solved while using this system. The amount of contaminants, the size and type of equipment used and the amount of pressure are some factors that contribute to the buildup of materials on the membrane, making it ineffective.
Moreover, chlorine in the water causes damage to some membranes. To prevent this, manufacturers install a carbon pre-filter to reduce the chlorine, as well as sediment pre-filters to prevent other fine particles to clog the membrane. Which, of course, are added costs.
On the whole, however, reverse osmosis is the leading water filtration system used by homes and many industries. So far, it had justified its costs and surpasses expectations from health authorities with regards to safety and cleanliness.