Reverse Osmosis And Distillation Compared

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					Reverse Osmosis And Distillation Compared

Today, there are two leading technologies in the water purification
markets, namely, reverse osmosis and distillation. Lately, however, there
is a controversy a-brewing among manufacturers of these water purifying
machines and devices. The following is a comparison between reverse
osmosis and distillation.

First, we shall examine each of these processes.

What is reverse osmosis?

According to its proponents, reverse osmosis (also known as hyper
filtration) is the finest water filtration system at the moment.

One of the contentions is that the process removes particles as small as
molecular ions from a solution. It purifies water by removing dissolved
salts, minerals and other impurities and brings back its taste, color and
its other properties.

Its other use is purifying other fluids such as ethanol and glycol
through the reverse osmosis membrane and straining out ions and

There are other very useful uses of reverse osmosis and its technology,
but the most common is in purifying water.

Reverse osmosis uses a semi-permeable membrane that allows the fluid
being purified to pass through while blocking the present contaminants.
These membranes have microscopic pores that are small enough only for
water molecules and not the others.

Today, most of the reverse osmosis technology also employs the method
called crossflow. This is where the membranes continually clean
themselves. As water passes through, the rest continues downstream and
sweeps the rejected substances away.

Reverse osmosis needs a driving force to pressure the fluid through the
membrane, and this is done by a common pump. The higher the concentration
of rejected fluid, the pressure needed grows higher as well.

At present, the technology of the reverse osmosis is capable of rejecting
bacteria, salts, sugars, proteins, particles, dyes, and other
constituents that have a molecular weight of greater than 150-250
daltons. Meantime, the ions are separated with the help of charged
particles. Ions with charge (like salt) are rejected by the membrane and
those with no charge (such as organics) are let in.

How does distillation work?

Distillation is a water purification process that uses a heat source.
Water is heated and vaporized to separate it from contaminants.
The heat is kept constant to prevent the other unwanted elements from
vaporizing. This is because water has a lower boiling point than salt and
other mineral sediments. Distillation also separates disease-causing
organisms from the water molecules.

Once all of the water has vaporized, the vapor is led into a condenser
where it is cooled, and reverts back to its liquid form into a receiving

The remaining elements, whose boiling points are too high for
vaporization, are left in the original container as sediment.
Distillation is often repeated to ensure that all sediments are left
behind in the process.

Many alcoholic beverages (brandy, gin, whiskey) are distilled with
apparatus similar to that used in water distillation.

Because of the cost of heating in the distillation process, solar power
was looked up as an efficient alternative. However, solar power only
works with relatively small amounts of liquid. Multiple distillations is
also out of the question because of time constraints.
More solar distillation experiments are still in progress, though.

Is a reverse osmosis unit like a distiller?

The processes are totally different. A distiller is like a tea kettle –
it boils water, catches the steam, and condenses it back into water.

Reverse osmosis strains the water with a very tight semi-porous membrane.
Both systems however rely on carbon filters to remove some chemicals.

Which water is purer – those produced by distillers or by reverse

Distillers remove sodium and other common minerals better than reverse
osmosis. But they are not that good in removing volatile chemicals with
low boiling point.

Reverse osmosis with the carbon filters remove chloramines (the current
favorite water disinfectant) best.

Both, however, produce very pure water. Actually, with reverse osmosis
and distillation compared, the only difference would be the economics of
ownership costs and maintenance expenses.