10 Best Water Purification For Travel

Updated on: May 2021

Best Water Purification For Travel in 2021

Potable Aqua Germicidal Water Purification Tablets

Potable Aqua Germicidal Water Purification Tablets
BESTSELLER NO. 1 in 2021

Potable Aqua Water Purification Tablets With PA Plus - Two 50 count Bottles

Potable Aqua Water Purification Tablets With PA Plus - Two 50 count Bottles
BESTSELLER NO. 2 in 2021
  • One Bottle of 50 Potable Aqua Germicidal Water Purification Tablets With One Bottle of 50 PA Plus
  • Makes contaminated water bacteriologically suitable to drink within 35 minutes
  • Effective against bacteria and Giardia lamblia
  • Emergency water purification tablets trusted by military and emergency organizations
  • Travel and camping accessory that improves taste and color of water

Aquatabs - World's Best Water Purification Tablets for Water Treatment and Disinfection - 2 Packs of 50ct (Total 100 Tablets)

Aquatabs - World's Best Water Purification Tablets for Water Treatment and Disinfection - 2 Packs of 50ct (Total 100 Tablets)
BESTSELLER NO. 3 in 2021
  • Each Aquatab is 49mg with 16.88% Sodium Dichloroisocyanurate creating 2.6ppm available chlorine. When dissolved in 2 quarts of water the easy to use tablets disinfect the water for safe drinking in as little as 30 minutes. For water that requires filtering and removal of dirt particles, such as water from a stream or river, use 1 tablet for every 0.75 liters of filtered water.
  • Protect you and your family during outdoor activities, natural disasters and emergency situations where boiling water is not an option. Be sure to read instructions before use.
  • Aquatabs are conveniently packaged to retain freshness and start with a 5 Year Shelf Life. Each Strip of Aquatabs contains 10 individually sealed tablets.
  • Tablets are so small that they easily fit into any pocket, pouch, purse, bag, backpack, drawer, emergency preparedness kit, disaster relief pack and more.
  • We are THE APPROVED seller of Aquatab.

Survimate Filtered Water Bottle BPA Free with 4-Stage Intergrated Filter Straw for Camping, Hiking, Backpacking and Travel

Survimate Filtered Water Bottle BPA Free with 4-Stage Intergrated Filter Straw for Camping, Hiking, Backpacking and Travel
BESTSELLER NO. 4 in 2021
  • 【Advanced purification System 】: Survimate purifier water bottles have 4 advanced high-performance purify installed, they are: Medical Grade Hollow Fiber Membrane, Coconut Shell Activated Carbon, Beads and Medical Grade PP Cotton.
  • 【Safe Like Baby Bottle】:Survimate Bottles are made from Food Grade Tritan Copolyester, without any bad smell, it's BPA-free, heat resisting and extremely durable.
  • 【Long Lifespan & Replaceable 】:No need to worry about replacing filters for up to 1500L/year of continuous usage. Replaceable filters save you money as the water bottles themselves have a very long life. (According to different water quality, the lifespan of the filter would be a little different.)
  • 【Ultimate Wilderness Survival Assistant】:This versatile water bottle not only helps providing healthy, drinkable water in harsh outdoor conditions, but will help you to find direction using the built-in compass on the top.
  • 【Instant Fresh Water】:Just fill up the bottle and drink. Nothing could be simpler - no pumps or hoses, no squeezing, no batteries or bulbs! Only sip 5 to 8 times to get clean water.

Aquatabs 100 Pack - World's #1 Water Purification Tablets

Aquatabs 100 Pack - World's #1 Water Purification Tablets
BESTSELLER NO. 5 in 2021
  • Aquatabs are effervescent tablets which kill microorganisms in water to prevent cholera, typhoid, dysentery and other water borne diseases. Clean drinking water is ready in 30 mins.
  • In the past year over 1 billion Aquatabs have been used globally. Each package includes 100 individually sealed tablets with up to 5 year shelf life.
  • Aquatabs are used both in emergency situations and also for continuous use in households that do not have access to safe drinking water.
  • The only water purification tablet with NSF 60 certification and approved formula for routine use by the World Health Organization (WHO)
  • Maximize shelf-life with water-proof / light-proof standup pouch. Instructions included.

Aquatabs 200 Pack - World's #1 Water Purification Tablets

Aquatabs 200 Pack - World's #1 Water Purification Tablets
BESTSELLER NO. 6 in 2021
  • Aquatabs are effervescent tablets which kill microorganisms in water to prevent cholera, typhoid, dysentery and other water borne diseases. Clean drinking water is ready in 30 mins.
  • In the past year over 1 billion Aquatabs have been used globally. Each package includes 200 individually sealed tablets with up to 5 year shelf life.
  • Aquatabs are used both in emergency situations and also for continuous use in households that do not have access to safe drinking water.
  • The only water purification tablet with NSF 60 certification and approved formula for routine use by the World Health Organization (WHO)
  • Maximize shelf-life with water-proof / light-proof standup pouch. Instructions included.

Aquatabs AQT100 Water Purification Tablets (Pack of 100)

Aquatabs AQT100 Water Purification Tablets (Pack of 100)
BESTSELLER NO. 7 in 2021
  • Trusted for over 20 years for use in emergency situations
  • Hurricanes - tornados - earthquakes - floods
  • Over 3 billion gallons of water treated annually
  • Fast acting. Water is ready to drink 30 minutes after mixing
  • Not unpleasant taste. Great tasting water consistently

LifeStraw Personal Water Filter for Hiking Camping Travel & Emergency Preparedness (Pack of 2)

LifeStraw Personal Water Filter for Hiking Camping Travel & Emergency Preparedness (Pack of 2)
BESTSELLER NO. 8 in 2021
  • Each Life Straw personal water filter will provide 1, 000 gallons (4, 000 liters) of safe drinking water without using chemicals, iodine
  • Removes 99. 9999% of bacteria including Escherichia coli (e-coli), campylobacter, vibrio cholera, pseudomonas aeruginosa, shield, salmonella
  • Removes 99. 9% of protozoa including giardia lamblia (beaver fever), cryptosporidium parvum, entamoeba histolytica
  • Perfect for your family and friends to use during camping, hiking and backpacking or for your emergency kits at your home, car and office
  • Pack of two Life Straw personal filters. Requires no electrical power, batteries or replacement parts. BPA free, chemical free

GRAYL Geopress 24 oz Water Purifier for Global Travel, Backpacking, Hiking, and Survival (Coyote Amber)

GRAYL Geopress 24 oz Water Purifier for Global Travel, Backpacking, Hiking, and Survival (Coyote Amber)
BESTSELLER NO. 9 in 2021
  • ONEPRESS GLOBAL PROTECTION: Empowers international travelers and outdoor adventurers to make the world’s sketchiest water sources safe and clean to drink. Ideal for global travel and outdoor adventures (hiking, camping, backpacking, fishing, hunting) and survival scenarios
  • REMOVES ALL PATHOGENS: Viruses, bacteria and protozoa - from any freshwater source on Earth. Filters pesticides, chemicals, heavy metals, and microplastics; improves taste
  • UNRIVALED EASE & SPEED: Effortlessly purifies 24 oz (710ml) of water in as quick as eight seconds. Requires no setup time, pumps, hoses, sucking, batteries, chemicals, or prolonged waiting. Simply – Fill. Press. Drink.
  • MAKES WATER TREATMENT EASY: Use your body weight on the SoftPress Comfort Pads to power purification. Drink and share safe, clean water through the SimpleVent Cap
  • AWARD WINNING ONEPRESS VERSATILITY: No straw, pump or gravity bag can match. Effortlessly fill from any spigot, hotel sink, murky river, taco stand, lake, or well.

Travel Berkey Gravity-Fed Water Filter with 2 Black Berkey Purification Elements

Travel Berkey Gravity-Fed Water Filter with 2 Black Berkey Purification Elements
BESTSELLER NO. 10 in 2021
  • 1.5 GALLON CAPACITY- The portable Travel Berkey Purification System effortlessly purifies water for about 1-3 people each day. The system is just 18” tall and 7.5” in diameter.
  • POWERFUL PURIFICATION- Berkey systems equipped with Black Berkey Purification Elements purify water—not just filter it—by removing greater than 99.999% of viruses and greater than 99.9999% of pathogenic bacteria, while also removing or dramatically reducing protozoa (such as giardia and cryptosporidium), trihalomethanes, inorganic minerals, heavy metals (including arsenic, lead, mercury, chromium), pharmaceutical drugs (including caffeine, Acetaminophen, Ibuprofen, Progesterone, Triclosan),
  • ECONOMICAL, LONG-LASTING- A pair of Black Berkey Purification Elements lasts for up to 6,000 gallons before needing replacement. Black Berkey Purification Elements average just 2 cents per gallon of purified water.
  • INDEPENDENT TESTING- Berkey by NMCL uses several independent third-party labs to test a broad range of potential contaminants and conducts Extreme Testing for lead and PFCs in order to show the effectiveness of our Black Berkey Purification Elements.
  • DRINK CONFIDENTLY VIRTUALLY ANYWHERE- No electricity, tools or plumbing required. Travel the world, prepare for emergencies, and take control of your family’s everyday drinking water with your Berkey gravity-fed water filtration system with Black Berkey purification elements. Enjoy delicious, nourishing water from the leader in gravity-fed water solutions.

Water Treatment Process: Disinfection

Learn about how and why water is disinfected. To prevent contamination in the water supply, chlorine disinfection, reverse osmosis or other methods must be used. For professionals, this article covers the costs, by-products and benefits of each method.

Different Methods

Many different methods of water purification are used today. For physical solids, the water may be distilled or it may pass through a filtration or sedimentation device. Biological processes like active carbon and sand filters may also be used. Chemically, the water can be treated with ultraviolet light, chlorine or a process known as flocculation. Each of these methods is intended to reduce the algae, parasites, particles and bacteria in the water.

To choose which method of purification to use, the water is initially tested to see what metals, pathogens and bacteria reside within it. Typically, three main tests are performed to ensure that water does not contain Giardia, viruses or Coliform bacteria. Coliform is normally found within the bodies of warm-blooded animals. It can also be found within the earth, water or air. If Coliform is present in water, it is a sign that other bacteria could be present. Water sources must be completely disinfected to ensure that all of the microorganisms are gone. According to current standards, water must be 99.9 percent free of Giardia and 99.99 percent free of other viruses. Coliform standards allow 0 Coliforms in one hundred millimeters of water. If a facility tests 40 samples every month, only one sample can ever test positive for the bacteria. In treatment plants that take more than 40 samples, less than five percent are allowed to have the bacteria present.

Why is Water Purified?

It is impossible to tell if water is truly clean by just looking at it. Rain water and lake water is exposed to animals, fungi and bacteria constantly. Due to this reason, the government and international associations have set standards that limit the maximum amount of contaminants allowable in potable water. In the past, people considered natural spring water appropriate for drinking. Since that time, even this natural source of water must be analyzed chemically and microbiologically for contaminants.

In 2020, the World Health Organization issued a report that stated that 1.1 billion people lacked access to potable water. Roughly 88 percent of the 4 billion cases each year of diarrhea occur due to inadequate water sanitation. Out of these cases, 1.8 million people die from the preventable contamination. Even simple at-home methods like boiling water or filtering it could significantly reduce the deaths from waterborne diseases.

Waterborne diseases are easily spread through water supplies that are not treated. In the past, people easily became infected with pathogens like Anthrax, Salmonella and Escherichia coli. Unclean water produced illnesses like cholera, tuberculosis, giardiasis, polio, Hepatitis A and cryptosporidiosis. To prevent the spread of disease, water must be treated to make sure that it is safe to drink. Since it is difficult to stop water from becoming filled with pathogens, most water treatment plants seek to purify water that is intended to be consumed. Overall, pathogens can be taken out of the water using a physical or chemical method. If water is stored with a chemical agent like chlorine, it can be held for longer periods of time without bacteria or viruses multiplying in it.

Before humans can consume safe drinking water, a water treatment plant must disinfect it. The goal of treatment facilities is not to sterilize water. Sterilization removes any organism in the water and is typically not necessary. The cheaper alternative of disinfecting water is an effective enough alternative.

Membrane Filtration

One of the most common ways to filter drinking water and sewage waste is to use a membrane filter. Any particle larger than 0.2 um can be filtered out so bacteria like giardia and cryptosporidium can easily be removed. This method is also effective for industry since it makes the water reusable, but not drinkable. Unfortunately, this method will not remove substances like nitrates or heavy metal from the water.

Removing Ions

When substances like heavy metal are dissolved in water, they must be removed by an ultra-filtration membrane. These are polymer membranes with tiny pores that filter out microscopic particles in the water. The water pressure required for ultra-filtration membranes depends entirely upon the kind of membrane media that is used. Ion exchange systems can also be used to remove unwanted ions and to replace them with benign Na+ or K+ ions. These alternative ions are more soap-friendly and help soften the water. Ion exchange is often used to remove lead, arsenic, nitrate and mercury from water.
Another common water cleaning method is known as precipitative softening. Hard water is treated with chemicals like calcium oxide or sodium carbonate. Once this treatment is done, any calcium carbonate in the water is removed.

To remove ions, the water may also be passed through a positive and negative electrode. Known as electro-deionization, this method causes ions with the opposite charge to move toward the appropriate electrode. Once this is done, it produces water that is only slightly less pure than ion exchange treatment. To completely remove ions, the water is typically treated with reverse osmosis and later deionized with electrodialysis.

Disinfecting Water

Many sources of water contain pathogens like Shigella, protozoa, giardia, cholera and salmonella. For people to drink water, these pathogens must be killed or filtered out. Since filtration can only remove larger pathogens, the liquid must also be treated with some type of chemical disinfecting agent. While the treatment process is going on, it is held in a contact tank or some type of temporary storage.
One of the most common ways to disinfect water is to treat it with chlorine. This method uses chlorine, chloramine or chlorine dioxide. As a strong oxidant, chlorine kills any pathogens extremely quickly. Unfortunately, chlorine gas is extremely toxic. Chlorine disinfection must be carefully supervised to prevent the gas from seeping into the environment. Sodium hypochlorite solutions can also be used to release free chlorine and make it safer. The solid form of chlorine, known as calcium hypochlorite, can immediately release the chemical into water. This method is not typically used because it requires a person to open bags and pour it into the water. With gas or bleach, the process can be automated and reduces the risk of human error.

Chlorine contains one large drawback compared to other purification methods. If there are certain organic compounds in the water, chlorine can have a negative chemical reaction that produces carcinogens. To prevent this, government authorities in the United Kingdom and the United States have both issued regulations limiting the amount of carcinogenic by-products in water. The last limitation of chlorine is that it is only minimally effective against protozoa like cryptosporidium and giardia. To reduce the risk of these protozoa entering the water supply, other methods of purification must be used in conjunction with chlorine disinfection.

In recent years, many cities have switched from using chlorine to chloramine. Although chloramine is easier to use, it seems to be a corrosive agent. It can cause pipes and materials in older systems to corrode. Afterward, lead leaches out into the city's water supply. As a neurotoxin, consumption of lead should be avoided in water supplies.

Pre-chlorination and Post-chlorination

Chlorine can be added either before the treatment process or after the primary treatment has occurred. These two uses are known as pre-chlorination and post-chlorination. Many treatments will use just post-chlorination or a mixture of the two options. With pre-chlorination, the chemical is added to water before it has been treated. This works well throughout the treatment process because some residual chlorine remains. It helps prevent algae growth at plant, limit mudballs and improve coagulation. Since it lasts for an extended period of time, chlorination can help improve the safety of badly contaminated water. One of the problems with pre-chlorination is that it gives the chlorine more time to create reactions with other substances. This can produce a known carcinogen known as trihalomethanes. By the 1970s, an increase in knowledge about this reaction led pre-chlorination to be used less in the United States. If it is used, the chlorine will normally be placed in the water supplying before flash mixing.

With post-chlorination, chlorine is added after the water is treated. This is one of the last steps before the water will enter a distribution system. It is intended to destroy any remaining pathogens. Since this final step is one of the most effective ways to provide chlorine residual to the supply, it is often used with every water treatment method. Post-chlorination is typically added after water exits the filter. It is then pumped into a clear well so that the chlorine has time to purify the water. At this point, the water can be placed in a storage container or sent to residential homes.

Chlorine Dioxide

For a faster-acting disinfecting, chlorine dioxide works well. It is not used very often because it can create chlorite which is only allowed in very small amounts in the United States. If it is used to disinfect water, it can spontaneously detonate.

Chlorine dioxide does not use chloramines, hypochlorous acid or breakpoint chlorination. The chemical symbol for chlorine dioxide is ClO2. This chemical is capable of killing viruses, bacteria, Giardia and Cryptosporidium. As chlorine dioxide is added to the water, it causes a process known as oxidization. This basically transforms organic matter into water and carbon dioxide. It does not create trihalomethanes and will not react with ammonia. This process is often beneficial because it does not produce unpleasant tastes or smells. Unlike other methods, chlorine dioxide can effectively work in high pH levels.

Despite its benefits, chlorine dioxide is not frequently used because it must be created onsite. This can be very expensive and require a large amount of technical knowledge. It also happens to be extremely combustible which can cause problems when workers handle the chemical.


In the last few years, chloramine has been increasingly used as a disinfection agent. It is not a particularly strong oxidant, but it lasts longer than free chlorine. Chloramine can be made by adding ammonia to water after chlorine is added. When the two chemicals react, it creates chloramine. Some distribution systems that use this method have to deal with nitrification. The presence of ammonia allows bacteria to grow and nitrates are produced.

Ozone Disinfection

Ozone is extremely toxic to the majority of waterborne organisms. It is an unstable molecule that is often used in Europe to destroy protozoa and other pathogens. To make ozone, oxygen is sent through an ultraviolet light. It must be created on-site and put into the water using bubble contact. Unlike chlorine, ozone does not contain any taste or odor. It also has fewer by-products than chlorination. One of the only by-products created using ozone is bromate. This suspected carcinogen is found in levels of more than 10 ppb in ozone disinfected water. After ozone is used, there is no residual disinfectant left in the water and it is recognized as safe by the United States Food and Drug Administration.


Ultraviolet light can be used to inactivate cysts as long as the water is still. In higher turbidity, ultraviolet light becomes less effective due to absorption problems. One of the issues with this disinfecting method is that there is no residual disinfectant left. After ultraviolet disinfection is used, other disinfectants must be added to ensure that the water remains pure.

Portable Methods

For remote locations or emergency situations, a portable method of disinfecting water can be used. Since these are only intended for emergencies, the taste or odor of the water may vary. There may also be some remaining chemical contamination in the water. Since the safety of the drinking water is not assured, these methods should only be used temporarily for short time periods.

Traditional methods of killing bacteria revolved around boiling water on a fire or oven. Since these two
methods add carbon dioxide to the environment, a low-cost alternative is solar water disinfection. It has a low impact on the environment and can be used in remote locations. The water has to be heated by sunlight. Once it is transferred to a dark storage area, Salmonella will start to multiply in the water. This can be prevented by adding ten parts per million of hydrogen peroxide.

Other Techniques

If water is heated to high enough levels, it will inactivate many of the micro-organisms in the water. At sea level, water must be boiled for at least one minute. When the water is heated at higher altitudes, it should be boiled for at least three minutes. In hard water locations, boiled water will cause calcium carbonate to build up on the kettle or boiling pot. If there are heavier metals in the water, boiling will not help. Any substance that has a higher boiling point than water will remain in the kettle. Since water vapor leaves during the boiling process, the boiled water will actually have a higher concentration of heavy metals. Since no residual disinfectant is used, the water will begin to harbor contaminants if it is stored for any amount of time.

Granular activated carbon filtering is used to absorb toxic substances. As water moves through the filter, the substances are drawn out. This method is typically used with water filters and fish tanks to remove organic contamination or unusual tastes. Some households will use carbon filtering or silver to improve the taste and odor of the water. When water is left in the carbon filter for long periods of time, micro-organisms can begin to grow. To prevent this, silver nanoparticles can be added to halt bacteria growth.

Another process used to treat water is distillation. When water is boiled, a vapor is produced. Once the vapor hits a cold surface, it condenses. The condensation can be collected and consumed since the harmful substances do not boil out of the water. Unfortunately, the distilled water may still not be completely pure because some substances have a lower boiling point than water. Like carbon filtering, distillation does not use a residual disinfectant so it cannot be stored before it is consumed. If it is consumed immediately after it is distilled, the water will be about 99.9 percent pure.

Reverse Osmosis

Reverse osmosis involves using pressure to push water through a semi-permeable membrane. This strains out any bacteria or substances and produces drinkable water. In theory, reverse osmosis is the most effective method to purify water on a large scale. Since a perfect membrane is difficult and potentially impossible to fashion, it cannot achieve its theoretical potential in practice.

Another type of membrane is used in direct contact membrane distillation. This uses a hydrophobic polymer to send water vapor from a warmer side to the cooler side. The temperature differences between the two sides works as a kind of vacuum to push the water vapor through the membrane.
Desalination is another method of producing pure water, but it is seldom because of its high cost. Salt water is distilled and sent through a semi-permeable membrane to remove impurities and salt. For desert areas, the method can effectively produce drinking water. It is far more expensive than other water sources and is rarely used on a large scale. In dry regions, desalination is only used for drinking water and select industrial uses due to its high cost.

Debates over Demineralized Water

When water is distilled, all of the natural minerals in the water are filtered out. This produces a less than ideal drinking water. Since 1980, the World Health Organization has looked into problems with demineralized water. Demineralized water leads to deficiencies in blood serum potassium as well as electrolytes. Reverse osmosis and nanofiltration cause the risk of toxic materials to increase because harmful elements are easily leached from piping. In infants, demineralized water has been linked to lead poisoning. According to the United States Environmental Protection Agency, water should contain at least 10 mg/L of magnesium and 20 mg/L of potassium.

Chlorination must be performed to remove manganese and iron. Since some water treatment processes can alter the taste of water, chlorination can effectively improve the smell or taste. It also effectively gets rid of gases like ammonia or hydrogen sulfide. Presently, this method is the most common way to disinfect water.

How Chlorination Chemistry Works

Chlorination is more than just adding chemicals to water. Once chlorine is added, it begins a mix of chemical processes with any substances in the water as well as the water itself. Chlorine residual is caused by some of these reactions and the resulting chemical destroys pathogens and organisms in the water.

As soon as chlorine is in the water, it starts to react with other compounds. Any organic compounds mixed with chlorine will cause the creation of trihalomethanes which are carcinogens. Hydrogen sulfides, nitrite, manganese and iron will also react. With hydrogen sulfide, the chlorine may react in two different ways.

It can either form H2S + Cl2 + O2- → S + H2O + 2Cl- or H2S + 4Cl2 + 4 H2O → H2SO4 + 8 HCl. In the first reaction, chlorine and oxygen react with hydrogen sulfide and chloride, water and sulfur is produced. The second possibility involves the chlorine and water reacting with hydrogen sulfide. This produces hydrochloric acid and sulfuric acid. In each of the two reactions, all of the chlorine is used up. The amount of chlorine that is used up is known as the chlorine demand. More chlorine must be added for the microorganisms in the water to be killed.

Chlorine Gas and Water Reactions

While chlorine reacts with other compounds, part of the chlorine will react with the water. Depending on the kind of chlorine, the type of reaction may vary. Chlorine gas, chlorine dioxide or hypochlorite can be added to the water. Every type of chlorine will kills viruses, bacteria and protozoans in the water, but a different form must be used depending on safety and efficacy.

The gaseous form of chlorine must be compressed into metal cylinders. It is exceptionally hard to handle because of its corrosive and toxic properties. If the concentration is high enough, it can even be fatal. Once chlorine gas is added to the water, it creates this reaction: Cl2 + H2O → HOCl + HCl. This results in hydrochloric acid and hypochlorous acid. Hypochlorous acid may break down in the right pH level into a hydrogen ion and a hypochlorite ion. This process can also be reversed to form hypochlorous acid again.

When the pH level of the water is higher, more ions are formed and less hypochlorous acid. Lower pH levels allow more hypochlorous acid in the water. This is extremely important because hypochlorous acid is a type of chlorine residual. Chlorine residual is the amount of chlorine leftover in the water that ensures that no pathogens can grow. For water to be stored and to remain pathogen free, some chlorine residual must be present.

Benefits and Drawbacks of Using Chlorine

Disinfecting with chlorine is commonly done because it is cheaper and inactivates pathogens in the water. With chlorine, water treatment facilities can prevent the growth of algae and remove iron from the water. In addition to removing manganese, it can destroy hydrogen sulfide and bleach organic colors. For large distribution systems, chlorine works great to control slime growth and restore pipeline capacity. It leaves a residual that can be easily controlled and has been successfully used for years. The only safety issues associated with using chlorine disinfectants is typically due to the difficulty of handling it. If more than 2,500 pounds of chlorine gas is stored, the facility must be monitored by the Occupational Safety and Health Organization as well as the United States Environmental Protection Agency. Among other negatives, chlorine may react with compounds to create undesirable by-products. If it is used in high amounts, it can produce an unpleasant taste or smell.

An Alternative to Gas: Hypochlorites

Rather than use chlorine gas, some water treatment facilities use hypochlorite. This form of chlorine is known to most laymen as bleach. Since it is less pure than chlorine gas, it is easier for facilities to safely handle the chemical. Unfortunately, hypochlorite tends to lose effectiveness if it is kept in storage for long periods of time. Any energy, heat or light can cause hypochlorites to break down while they are in storage.

There are three basic kinds of hypochlorites: bleach, sodium hypochlorite and calcium hypochlorite. Calcium chlorite is a solid that must be mixed with water to create a solution. It is 65 to 70 percent concentrate. Sodium hypochlorite is formed with 12 percent chlorine and is a liquid. Commercial bleach is occasionally used and it is basically the same product that consumers can purchase at a store. Different brands contain a variety of concentration levels that range from 3.5 to 5 percent. All bleaches and hypochlorites work the same way that chlorine gas does to disinfect water. The primary difference between the different disinfectants is due to how they are handled and added to water.

The Science Behind Chloramines

Instead of hypochlorous, some water treatment facilities use chloramine. To create chloramines, chlorine gas or some hypochlorite must be placed in the water to create hypochlorous acid. Afterward, ammonia must be added. The ammonia reacts with hypochlorous acid and becomes chloramine.

Altogether, there are three different kinds of chloramines that can be created in water. These three types are trichloramine, monochloramine and dichloramine. To form monochloramine, hypochlorous acid must react with water. Afterward, the monochloramine reacts with additional hypochlorous acid to create dichloramine. To create the last form of chloramine, the monochloramine must combine and react with hypochlorous acid to create trichloramine. Scientifically, these three processes would be written like this:
Monochloramine- NH3 + HOCl → NH2Cl + H2O Dichloramine- NH2Cl + HOCl → NHCl2 + H2O Trichloramine- NHCl2 + HOCl → NCl3 + H2O

To modify the number of reactions, the pH of the water has to be changed. No matter what, monochloramines and dichloramines will be created and can be used as disinfecting agents. Together, these are known as combined chlorine residual because it is mixed with nitrogen. This type of chlorine residual is different than the free chlorine residual that is created in other kinds of chlorination.
Chloramine is more stable than chlorine and also weaker. It is typically used in distribution lines because it effectively kills bacteria and protozoans. Unfortunately, they break down due to light heat or bacteria and are also not effective at destroying viruses.

Breakpoint Chlorination

When dealing with water treatment plants, it is very important to understand the concept of breakpoint chlorination. As chlorine is added to water, it forms a series of reactions. The breakpoint chlorination level is reached when no more reactions can occur and some residual chlorine remains. First, water and reducing compounds react. This uses up the entire amount of chlorine. When more chlorine is added, it reacts with ammonia and organic matter that is in the water. This creates a chlorine residual known as chloramines. If chloramine is the disinfecting chemical used, additional ammonia must be used. At this point, chloramine is almost at the breakpoint. The benefit of chloramine is that it creates minimal amounts of trihalomethane, but it can change the odor of the water.

If hypochlorous acid is used, then chlorine must be added past this point. The chlorine will gradually cause the chloramine to break down and will decrease the level of chlorine residual. At this time, the water is finally at the breakpoint. This moment in time is when all of the chlorine demand has been fulfilled. Each ammonia and reducing agent has reacted with the disinfecting agent. Any chlorine input at this point will push the water past the breakpoint. Chlorine will cause a reaction that creates hypochlorous acid. Altogether, this process is known as breakpoint chlorination and is the most frequently used kind of chlorination. Only enough chlorine is used to push the water over the breakpoint and allow it to have free chlorine residual.

Controlling Disinfection By-Products

Different disinfection processes will create a variety of by-products and amounts. The concentration of chlorine, dosage and temperature of the water can impact the creation of by-products. In addition, the pH level of the water and amount of organic compounds can change the amount of by-products formed. There are several ways to limit halogenated byproducts. According to the Environmental Protection Agency, by-products must be removed as soon as they are formed. This is expensive and difficult, so the two other methods are often used. Some water treatment facilities use different disinfectants that do not make by-products. Alternative disinfectants are overall cheaper than removing disinfectants that have already been formed. The last way to limit by-products is to eliminate or reduce the amount of organics in the water. Since chlorination and oxidation react with organic matter, limiting the amount of organic matter can reduce any negative by-products.


EPA Water Regulations Guide
Wisconsin State Laboratory of Hygiene

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