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Water Treatment Alternatives

There is a wealth of water treatment alternatives currently on the market. The proponents of these various water treatment alternatives will often make several promises about their product, and it may become difficult to assess, even for the most conscientious of consumers, the appropriate water treatment product for one's needs. To aid you in your choice of water treatment, we have provided a brief explanation of three of the most common water treatment alternatives. In the following paragraphs, you can read about the processes and best uses of reverse osmosis, distillation, and filtration.

Reverse Osmosis
Reverse osmosis is a process of water treatment that has risen in popularity since the 1970s. Primarily used as a method of desalinating seawater, the reverse osmosis process involves a semi-permeable membrane—usually constructed from a polyamide-based material—and a source of pressure. Water is forced to move against its natural flow pattern (osmosis) from a solution of high saline concentration to a solution of low saline concentration through the semi-permeable membrane.

The object of reverse osmosis is to block the passage of salt particles through the membrane, resulting in a solution of purified water on one side of the membrane and a solution of highly concentrated, salt water on the other side.

In recent years, reverse osmosis has been adapted to treat freshwater for drinking water purposes. While reverse osmosis is highly effective at desalinating seawater, there are some aspects to the process that make it undesirable for treating drinking water. First of all, the semi-permeable membrane is only designed to remove particles from water that are physically larger than water molecules. The membrane will remove mineral components and most heavy metals from drinking water, but it will not remove chlorine and other synthetic chemicals. Such chemicals are physically smaller than water molecules and can pass easily through the membrane. Besides this drawback to reverse osmosis, the process is rather wasteful and costly. Generally, three gallons of water are wasted for every one gallon of purified water produced.

The distillation process--used primarily as a means of producing alcoholic beverages--has existed for millennia. Distillation reached its peak of popularity in the 1970s, but due to its costliness and general inefficiency as a water treatment process, it has now been largely relegated to the purposes of scientific laboratories and printing shops. Still, distillation continues to be used--in small measure--as a method of drinking water purification and merits some discussion.

In the distillation process, contaminated water is heated until it reaches its boiling point. Once the water has begun to evaporate, the heat is kept at a constant to ensure that contaminants with a higher boiling point than water do not also evaporate. The steam from the water is led through a series of tubes into a separate container where it is allowed to condense into the liquid form.

The object of distillation is to produce pure water in the second container while retaining any contaminants in the first container.

Distillation, because of its constant heat source, will remove any contaminants with a higher boiling point than water. Such contaminants include minerals, heavy metals, and many chemicals from pesticide runoff. They do not include chlorine and VOCs , which have a lower boiling point than water. Consequently, distillation is not highly effective at providing safe drinking water. Like reverse osmosis, it is also incredibly inefficient, wasting nearly 80% of the water it uses.

Filtration has emerged in the last two decades as the forerunner of water treatment technology. Its innovative process is the only purification technique than can effectively remove chlorine—the primary contaminant of municipally treated water.

The filtration process utilizes a filter media through which water passes. Such filter media range from sand for older filters and solid block carbon or carbon media mixtures for newer filters. The filtration process generally involves several stages, through which contaminants are removed or reduced in order of importance. In the first stage of filtration, the more concentrated chemicals, like chlorine and VOCs, are significantly reduced. This preliminary reduction allows the remaining stages of filtration to focus on contaminants like pesticides and tiny microbes that are more difficult to filter. The subsequent stages of filtration focus on the reduction of lead and chemicals from pesticide runoff. As the water passes through the stages of filtration, contaminants are both physically and chemically blocked from passage through the filter media.

Contaminants that are physically larger than the granules of the media will be blocked from passage while other undesirable elements of drinking water (such as chlorine and VOCs) are encouraged to break their chemical bond with the water molecules and attach to the filter media.

One of the primary reasons why filtration has become the forerunning method of water treatment in recent years is its use of both chemical and physical processes to block contaminant passage. Solid block carbon and multimedia filters are not merely the only water treatment products that can remove chlorine and reduce VOCs in drinking water; they are also capable of retaining healthy, pH-balancing minerals in drinking water. The adsorptive process of such filters attracts chlorine and VOCs to the filter media while allowing mineral sediments to pass through the filter.

What about Bottled Water?

Read Bottled Water: Is it Hip or Hype? to learn some little-known facts about bottled water.

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