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Brushing up on water treatment 101, part 3
In this last section of a three-part series, the use of ozone, ionization, distillation and aeration is discussed in a simple fashion to help the beginner rationalize the importance for a full understanding of these technologies and the need, again, for a professional water treatment specialist.
This is the final article in a three-part series discussing water chemistry and technology basics.
In this last section of a three-part series, the use of ozone, ionization, distillation and aeration is discussed in a simple fashion to help the beginner rationalize the importance for a full understanding of these technologies and the need, again, for a professional water treatment specialist. Each of these subjects has had much written about them, and an assault of information in magazines, books, libraries and the Internet can be found. Water treatment and the technologies involved are vast and complex, as is the water to be treated. No two water sources ever seem to be the same, and what may work for one source and application may fail with another. A high-quality analysis of both the application and the raw water needs to be addressed before a treatment can be rendered.
Ozone, or O3, has been around since time began. Lightning produces ozone during thunderstorms and cleanses the air. The sun produces ozone when it strikes hydrocarbons in the atmosphere and cleanses the air we breathe by producing ozone with ultraviolet (UV) light. O3 is a naturally occurring, strong oxidizing and disinfecting agent. Elemental oxygen exists as two atoms of oxygen combine to form the O2 molecule. An unstable allotropic form of the gaseous oxygen occurs when UV rays from the sun strike the O2 molecule, break the bonds and form single oxygen atoms. A portion of these split atoms recombines with other O2 molecules to form O3. The energy released by lightning produces the same results and one can smell the fresh scent of the air after a thunderstorm. Photocopying machines and other electrical equipment produce ozone in small but noticeable quantities as well. Even though ozone has been protecting mankind since the beginning of time, it wasn’t until 1783 that a Dutch scientist, Van Marum, made the discovery. Christian Schönbein, a German scientist, named the substance “ozone” in 1840 after the Greek word “ozein” (meaning to smell) because of its unique odor. Ozone has a sharp, distinct, pungent odor beginning at concentrations as low as 0.02 ppm. Inhalation of ozonated air with one-tenth of a part per million by volume may cause irritation of the eyes, upper respiratory system and lungs as well as headaches.
Manufactured ozone generators produce O3 by exposing oxygen molecules to UV radiation or high electrical discharge. The weak bond in ozone makes this substance very unstable and, due to this instability, an oxidizing reaction occurs. The collision between the ozone molecule and an oxidizable substance such as inorganic materials (i.e., iron and manganese) or organic materials (i.e., plastics, rubbers and microorganisms such as bacteria, viruses and parasitic cysts) make this substance very good at removing or precipitating contaminants out of water and air.
Ozone has been used for many years in water treatment. Documentation dates back to 1906 when the municipality of Nice, France, used ozone for disinfection of its drinking water. The first commercial pool in the United States to use ozone was in Brynam, N.J., dating back to 1937. An ozone system was displayed at the New York’s World Fair in 1939 and was touted as the future of water treatment. The first ozone water treatment system to be used for municipal water treatment in the United States was used in Whiting, Ind., in 1940. Since that time ozone has gained wider acceptance, and the technologies used to produce ozone have become more cost efficient. Los Angeles and Dallas have the largest ozone plants in the world for treating their cities’ drinking water, and Las Vegas, Nev., began construction in 1998 of a treatment facility that is just as large. So, ozone is not new but is more accepted and cost-effective and is becoming a viable option in the water treatment industry.
Without going into a lot of detail on the properties of ozone as they are very complex, the uses of ozone are numerous if applied correctly and dosed properly. Ozone is not the cure all by any means, but it does have advantages over chemical dosing and is safer and more environmentally friendly. It is the most powerful oxidizer that can be safely used in water treatment. Not only is it great for treating drinking water, its use is widely applied in bottled water plants, ultrapure waters, swimming pools, spas, ponds, cisterns, breweries, aquariums, soft drinks, cooling towers and many other applications. Remind customers that this treatment technology needs to be addressed by a water treatment professional who has experience in this field in order to achieve the desired end results.
Distillation is another technology that has been around a long time and even today continues to be used as a water treatment solution. The basic concept is seen in nature as the hydrological cycle. As the sun evaporates water from sources such as lakes, streams, rivers and oceans the vapor contacts cooler air and recondenses to form dew or rain. This process is imitated artificially and more rapidly than in nature by using alternative sources of heating and cooling. Anyone who has accidentally boiled a pot of water until there was no water left is familiar with this process and the crust of contaminants left behind after the water is gone. Distillers use this same process, but they capture the steam. As the steam is condensed back into the liquid form, it is contaminant-free.
The water is bacterial free, but the cost can outweigh the benefits. Over the years these systems have become more efficient and cost-effective for producing larger amounts of water. Some systems can produce millions of gallons of water a day and remove a variety of contaminants if designed properly. These superheated units use steam pressure to flash vaporize some of the cooler water in each chamber. Each chamber is self-sustaining in nature and, therefore, is very efficient with the electric or gas heating element required. Both the multistage and vapor compression distillers can incorporate various forms of filtration to make up an effective treatment. These systems require water that is softened in order to be practical to prevent debilitating scaling and the resultant heat transfer losses and maintenance costs. Distillation is used in arid regions that are adjacent to oceans for distilling seawater for drinking water. Distillation also has been used for removal of such impurities as arsenic, benzene, lead, nitrates, trihalomethanes and radium, to name a few.
Aeration is a method that is used by nature as a means of water purification. This method has been observed by everyone who has seen a waterfall, crashing wave or white-water rapids. All of these methods transfer air into water and provide oxygen so the aerobic bacteria can survive. Aerobic bacteria require oxygen to survive and decompose plant material in water. However, these “good bacteria” need oxygen to work and burn up the supply of oxygen in the water. When the oxygen in the water is exhausted, anaerobic (or non-oxygen using) “bad” bacteria begin to decompose the plant material, and this is when water begins to smell and taste bad due to gasses that are released. Ferrous iron becomes ferric iron when exposed to oxygen. Aeration is a method to precipitate this type of iron into an insoluble form of iron that can be filtered. Other impurities such as hydrogen sulfide can be aerated out of water. Ponds, cisterns and lagoons can use aeration devices that use an air stone to transfer air to water. Water that becomes stagnant begins to grow algae and waterborne parasites.
Ionization is defined as the loss or gain of an electron. Copper and silver ionization is the loss of an electron that is created by applying a charge to an anode and forcing the electron off and into the stream of water. This small particle that becomes suspended in the water has bacterial disinfection qualities. Colloidal copper and silver have significant effects on many bacteria, viruses and impurities in water. Copper is very effective against algae and this electrically charged water also keeps bicarbonates such as calcium and magnesium in suspension longer by reversing the effects of static electricity caused by the flow of water within a pipe. This phenomenon reduces the risk of scaling in pipes because of these heavy minerals.
Other benefits also have been observed. The reduction of chlorine is one effect that is caused by the use of ionization. Since the copper and/or silver take the brunt of the disinfection process, the need for chlorine is reduced. Swimming pool owners and cooling tower operators have used this method of water treatment for a number of years. There have been many studies done that prove this method of bacteria and algae reduction is effective.
Copper and silver ionization is not new technology but, like ozone, it has not been used, understood or applied correctly. This type of water treatment dates as far back as the Egyptian era when they used copper and silver containers for water. In addition, the pioneers crossing the United States used copper and silver coins for water purification. Copper pennies thrown in wishing wells helped keep the bacteria and algae from growing. However, today we use electronic controllers to dose the correct amount of copper into the water, and each application can benefit when properly measured and applied.
As one may have learned from all the technologies that have evolved over the years, water treatment is an interesting and challenging occupation. The science of water chemistry and the understanding of water treatment technology are very complex. Every water source and application in the world is slightly different, and the desired result can be a challenge for a water treatment professional. The preceding articles only scratched the surface of what is available in water treatment and how to treat water effectively and efficiently. A knowledgeable water specialist should be employed with most every water treatment so the proper analysis can be made and the best method of treatment determined.
Parts one and two of this article may be viewed in the article archives at www.waterinfocenter.com.