Distillation is a process that separates the components of a liquid mixture based on the different volatilities of these components when the mixture is heated to boiling. Its various uses range from producing distilled alcoholic beverages out of fermented solutions, to separating crude oil into its various forms for specific consumer use, to removing impurities from water.
Water Purification Using DistillationDistillation is among the oldest water purification methods, with its beginnings dating back to the first century AD. The earliest accounts of distillation included those of Greek sailors using the process to convert sea water to potable drinking water.
Other than its widespread use in desalination that continues even to this day, distillation can also effectively purify water fouled by natural and unnatural contaminants including bacteria, nitrates, dangerous heavy metals like lead, arsenic, and mercury, and many volatile organic compounds or VOCs.
Given its capability to remove most bacteria and viruses and convert huge amounts of brackish and contaminated water into clean drinking water, distillation is the established method of water purification in countries where the sea is the only available source of abundant water supply, and in areas where the risk of water-borne diseases is high.
However, while distillation is considered as one of the treatment technologies that can reduce the broadest range of contaminants, it is not without its disadvantages. For one, along with removing potentially life-threatening substances, the process also strips water of its natural trace elements, many of which are crucial to the body’s proper functioning.
How Does Distillation Work?The distillation process basically mimics nature’s hydrologic cycle wherein the heat of the sun causes surface water to evaporate, the cooler air temperature causes the vapor to condense into clouds, and finally, water goes back to the Earth’s surface as rain, dew, snow, and other forms of precipitation.
A typical distillation system today utilizes alternative sources of heating and cooling to vaporize water and then condense the steam, thereby removing salts, trace metals, bacteria, minerals, asbestos, and other organic chemicals.
The process starts when the raw, untreated water is heated and brought to a boil to produce water vapor. This separates the pure water molecules from contaminants that possess a higher boiling point. As the temperature is kept constant, the water continues to vaporize while the less volatile contaminants remain in the original container. Removed from the heat source, the steam condenses back into water form, and guided through a series of tubes, is collected in a separate container.
To ensure the complete separation of water and other substances, the distillation process may be repeated several times until pure drinking water, void of all forms of contaminants, is produced.
Disadvantages of Drinking Distilled WaterThe mineral-free water produced from distillation has a wide range of applications in chemical and biological laboratories, as well as in the automotive and printing industry. As a form of water treatment however, distillation is not the most ideal.
As noted earlier, it does not only remove unwanted contaminants but vital natural minerals along with them. Because these natural occurring minerals may be essential to the body’s processes, there are medical professionals who advocate against drinking distilled water.
A study conducted by the Journal of General Internal Medicine on the mineral contents of US water bodies showed that North Americans have access to drinking water that have high levels of calcium, magnesium, and sodium. The study therefore did not recommend purifying water from these sources using distillation, as the process will put the mineral content to waste.
Further, a paper published by the World Health Organization (WHO) in 2004 outlined the harmful effects of drinking demineralized water. By definition, demineralized water is that which is nearly or entirely free of minerals, as distilled water is.
Among the potential health risks of drinking water with low- or zero-mineral content listed in the WHO document are the reduction of water content within the body cells, increased discharge of liquid and minerals from urine, an imbalance of sodium and chloride ions, and with continued consumption, improper functioning of the cell membranes.
Natural waters such as surface water or groundwater, even when deemed safe for drinking, are never found to be chemically pure. Significant amounts of minerals and organic matter of natural origin are always contained in these sources, leaving a characteristic taste to the drinking water. Demineralized water in contrast, gives a flat taste.
Aside from the possible negative health effects that the continuous intake of low-mineral distilled water can cause, the distillation process is also found to be deficient as a water purification technology because it is unable to remove other hazardous drinking water contaminants: pesticides, herbicides, chlorine, and chlorination by-products. These synthetic chemicals have lower boiling points than water and are therefore carried over into the condensate.
The cost of distillation is another disadvantage of this water purification technology. To be able to produce sufficient quantities, enormous amounts of energy are needed for the heating and cooling processes.
While improving the efficiency of the distillation equipment would help minimize operational costs, even then, the actual production of purified water can be a very slow and extremely wasteful process. In fact, about 80% of the original quantity is disposed of together with the remaining contaminants. Five gallons of untreated water therefore, can only produce one gallon of clean drinking water.