What are the benefits and risks of water chlorination?
Nov 27, 2016 · Chlorination is one of many methods that can be used to disinfect water. This method was first used over a century ago, and is still used today. It is a chemical disinfection method that uses various types of chlorine or chlorine-containing substances for the oxidation and disinfection of what will be the potable water source.
Why is chlorine added during water treatment?
Chlorination is the process of adding chlorine to drinking water to kill parasites, bacteria, and viruses. Different processes can be used to achieve safe levels of chlorine in drinking water. Using or drinking water with small amounts of chlorine does not cause harmful health effects and provides protection against waterborne disease outbreaks.
Why is chloramine used for water treatment?
Water chlorination, also known as disinfection, is the process of adding chlorine or chlorine compounds such as sodium hypochlorite to water. This method is used to kill bacteria, viruses, and other microbes in water. In particular, chlorination is used to prevent the spread of waterborne diseases such as cholera, dysentery, and typhoid.
Is chloramination an alternative to chlorination?
Chlorination is one of many methods that can be used to disinfect water. This method was first used over a century ago, and is still used today. It is a chemical disinfection method that uses various types of chlorine or chlorine-containing substances for the oxidation and disinfection of what will be the potable water source.
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Chlorination is a method of disinfecting water using a chlorine based chemical, or another substance containing chlorine to treat the water source. The history of water chlorination The idea of water chlorination was first proposed in Sweden during the 1740s.
What are the method of chlorination?
The different types of chlorine disinfection are batch disinfection, simple chlorination, super-chlorination followed by dechlorination, and shock chlorination. They vary in the amount of chlorine used. Batch disinfection treats water in batches when the chlorine demand fluctuates.Aug 23, 2019
What is meant by chlorination?
verb (tr) to combine or treat (a substance) with chlorine. to disinfect (water) with chlorine.
How is water chlorination done?
Many impurities in the water require a large amount of chlorine to react with all the impurities present. The chlorine added must first react with all the impurities in the water before a chlorine residual is present. The amount of chlorine that is required to satisfy all the impurities is termed the 'chlorine demand.Jan 23, 2017
What is chlorination and ozonation in water treatment?
Chlorination and ozonation are two types of drinking water purification processes. The key difference between chlorination and ozonation is that chlorination is the process of disinfecting drinking water with chlorine, whereas ozonation is the process of disinfecting drinking water with ozone.Feb 24, 2020
What type of reaction is chlorination?
Chlorination reaction, a halogenation reaction using chlorine.
What is chlorination why it is important?
CHLORINE FOR WATER “Chlorine is used to destroy disease-causing organisms in water, an essential step in delivering safe drinking water and protecting public health. Chlorine is by far the most commonly used disinfectant in all regions of the world.”Jun 28, 2010
Is chlorination of water safe?
Is chlorinated water safe to drink? Yes. The U.S. Environmental Protection Agency (EPA) limits the amount of chlorine in drinking water to levels that are safe for human consumption. The levels of chlorine used for drinking water disinfection are unlikely to cause long-term health effects.Apr 4, 2019
What are the advantages of chlorination?
The benefits of chlorination are: Proven reduction of most bacteria and viruses in water. Residual protection against recontamination. Ease-of-use and acceptability. Proven reduction of diarrheal disease incidence.
What is the process of adding chloramine to drinking water to disinfect it and kill germs?
Chloramination is the process of adding chloramine to drinking water to disinfect it and kill germs. It is sometimes used as an alternative to chlorination. Chloramines are a group of chemical compounds that contain chlorine and ammonia.
When was chlorine first used?
Chlorine was first used in the United States as a major disinfectant in 1908 in Jersey City, New Jersey. Chlorine use became more and more common in the following decades, and by 1995 about 64% of all community water systems in the United States used chlorine to disinfect their water.
What is the best disinfectant for drinking water?
Several major U.S. cities such as Philadelphia, San Francisco, Tampa Bay, and Washington, D.C. use chloramine to disinfect drinking water. Chloramine is recognized as a safe disinfectant and a good alternative to chlorine.
What is the EPA's water treatment system?
The U.S. Environmental Protection Agency (EPA) allows drinking water treatment plants to use chloramine and chlorine to disinfect drinking water. Water system pipes develop a layer of biofilm (slime) that makes killing germs more difficult.
What is the EPA's hotline for chloramine?
EPA provides guidance for local water authorities switching to chloramine on how to minimize lead and copper levels. If you are concerned about lead or copper levels in your household water, call EPA’s Safe Drinking Water Hotline at 800-426-4791 for testing information.
Where is chloramine used?
Chloramine has been used as a drinking water disinfectant in the United States in places like Cleveland, Ohio, Springfield, Illinois, and Lansing, Michigan since 1929. In 1998, an EPA survey estimated 68 million Americans were drinking water disinfected with chloramine.
What is the purpose of water in dialysis?
During dialysis, large amounts of water are used to clean waste products out of a patient’s blood. Dialysis centers must treat the water to remove all chemical disinfectants, including chlorine and chloramine, before the water can be used for dialysis.
What is chlorination in water?
Chlorination is a water treatment process that is used to eliminate certain pathogens, particularly in drinking water, such as dysentery and typhoid. Water treatment processes such as coagulation, filtration and sedimentation are used to battle waterborne diseases. For over a century, however, chlorination has been used to create water ...
When is chlorination performed?
Chlorination can also be performed during any part of the water treatment process, including: Pre-chlorination – almost immediately after water enters the treatment facility. After sedimentation and prior to filtration. During the disinfection stage of the water treatment process – most of the time, chlorination occurs at this stage.
What is the role of calcium hypochlorite in food?
Calcium hypochlorite also plays a major role in industrial food processing, killing germs and keeping our food supplies safe. For example, if you have water stored in a large tank, adding the right about of calcium hypochlorite with the help of a chlorination system will help disinfect the water.
What is the most common compound used in water treatment?
Calcium hypochlorite: Chlorine hypochlorite is the most common compound of chlorine used in residential water treatment. Calcium hypochlorite increases the pH of the water it is being used to treat and can be sold as calcium hypochlorite pellets or granules. Calcium hypochlorite should also be handled with care as it is capable ...
What is chlorine used for?
Chlorine is most commonly used in water treatment for as a disinfectant, though seldom in its pure form. Chlorine gas, sodium hypochlorite and calcium hypochlorite are the three most common chlorine compounds used in water treatment.
What happens during the disinfection stage of water treatment?
During the disinfection stage of the water treatment process – most of the time, chlorination occurs at this stage. Coagulation: untreated water enters the treatment plant and liquid aluminium sulphate is added, causing tiny dirt particles in the water to stick together.
When was chlorine first used in water?
The use of chlorine in water treatment has been around since 1893 and permanent water chlorination began in 1905. Hamburg, Germany was the first to attempt chlorinating drinking water, shortly followed by Maidstone, England, as a way to make water completely germ-free.
What is the chemical that is added to water during the treatment process?
Any type of chlorine that is added to water during the treatment process will result in the formation of hypochlorous acid (HOCl) and hypochlorite ions (OCl-), which are the main disinfecting compounds in chlorinated water. More detail is provided later on in this fact sheet.
When was chlorine first used?
Chlorine was first discovered in Sweden in 1744. At that time, people believed that odours from the water were responsible for transmitting diseases. In 1835, chlorine was used to remove odours from the water, but it wasn't until 1890 that chlorine was found to be an effective tool for disinfecting; a way to reduce the amount of disease transmitted through water. With this new find, chlorination began in Great Britain and then expanded to the United States in 1908 and Canada by 1917. Today, chlorination is the most popular method of disinfection and is used for water treatment all over the world.
What are the by-products of disinfection?
number of different by-products can be produced from the reactions in the disinfection process. By-products created from the reactions between inorganic compounds and chlorine are harmless and can be easily removed from the water by filtration. Other by-products, such as chloramines, are beneficial to the disinfection process because they also have disinfecting properties. However, there are undesired compounds that may be produced from chlorine reacting with organic matter. The compounds of most concern right now are trihalomethanes (THMs) and haloacetic acids (HAAs). THMs and HAAs are formed by reactions between chlorine and organic material such as humic acids and fulvic acids (both generated from the decay of organic matter) to create halogenated organics. A greater level of THM formation has been found in surface water or groundwater influenced by surface water.
What happens when bromine is in water?
Bromine in the water can result in the production of undesired compounds. Bromine ions can react with hypochlorous acid to create hypobromous acid. Hypobromous acid also has disinfectant properties and is more reactive than hypochlorous acid. Hypochlorous acid or hypobromous acid will react with organic material in the water and create halogenated by-products, such as trihalomethanes.
What is sodium hypochlorite?
Sodium hypochlorite (NaOCl) is made up of the sodium salts of hypochlorous acid and is a chlorine-containing compound that can be used as a disinfectant. It is produced when chlorine gas is dissolved into a sodium hydroxide solution. It is in liquid form, clear with a light yellow color, and has a strong chlorine smell. Sodium hypochlorite is extremely corrosive and must be stored in a cool, dark, and dry place. Sodium hypochlorite will naturally decompose; therefore it cannot be stored for more than one month at a time. Of all the different types of chlorine available for use, this is the easiest to handle.
What pH is used to disinfect water?
Because hydrogen ions are produced, the water will become more acidic (the pH of the water will decrease). The amount of dissociation depends on the original pH of the water. If the pH of the water is below a 6.5, nearly no dissociation will occur and the hypochlorous acid will dominate. A pH above 8.5 will see a complete dissociation of chlorine, and hypochlorite ions will dominate. A pH between 6.5 and 8.5 will see both hypochlorous acid and hypochlorite ions present in the water. Together, the hypochlorous acid and the hypochlorite ions are referred to as free chlorine. Hypchlorous acid is the more effective disinfectant, and therefore, a lower pH is preferred for disinfection.
How is calcium hypochlorite made?
Calcium hypochlorite (CaOCl) is made up of the calcium salts of hypochlorous acid. It is produced by dissolving chlorine gas (Cl2) into a solution of calcium oxide (CaO) and sodium hydroxide (NaOH). Calcium hypochlorite is a white, corrosive solid that comes either in tablet form or as a granular powder. Calcium hypochlorite is very stable, and when packaged properly, large amounts can be purchased and stored until needed. The chemical is very corrosive however, and thus requires proper handling when being used to treat water. Calcium hypochlorite needs to be stored in a dry area and kept away from organic materials. It cannot be stored near wood, cloth or petrol because the combination of calcium hypochlorite and organic material can create enough heat for an explosion. It must also be kept away from moisture because the tablets/granular powder readily adsorb moisture and will form (toxic) chlorine gas as a result. Calcium hypochlorite has a very strong chlorine odour – something that should be kept in mind when placing them in storage.
Why is chlorination important?
Another benefit of chlorination is that it can be carried out at any point in the water treatment process. Separate doses of chlorine might be added at many different stages through the process to ensure the water is treated effectively.
Why add chlorine to water?
Adding chlorine at this stage gets rid of any algae or other living organisms in the water so that this doesn’t cause issues at later stage. If water is pre-chlorinated at this stage it can stop smells and strange tastes in the water.
What is the process of disinfecting water?
The chlorination of water is a tried and tested treatment technique that has been around for over a century and it’s still commonly used today. Chlorination is a method of disinfecting water using a chlorine based chemical, or another substance containing chlorine to treat the water source.
How much chlorine is needed to reach breakpoint?
Anything between 10 and 15 times more chlorine than ammonium is needed to reach breakpoint. A common issue with smaller water treatment plants is not adding enough chlorine in proportion to ammonium, resulting in ineffective disinfection which can have serious consequences.
Which is more effective, chlorine or hypochlorous acid?
The more effective of the two compounds is hypochlorous acid. The levels of both types of compound is largely determined by the acidity or alkalinity of the water before the chlorine is added. If the water pH tends towards the acidic range, then there will be more hypochlorous acid available.
What is pre chlorineation?
Pre-chlorination refers to the process of adding chlorine to water as soon as it enters the treatment plant. Chlorine is usually added straight into the raw water or into a mixing vessel, which makes sure that the chlorine is evenly spread throughout the body of water being treated.
How does chlorine work?
Chlorine works by damaging the cell membrane which surrounds a microorganism. When the membrane is damaged, the chlorine then gets into the cell and stops both respiration and DNA activity. Without both of these processes, the cell is unable to survive and so dies off.
When is chlorine added to water?
During pre-chlorination, chlorine is usually added to raw water after screening and before flash mixing. Post-chlorination, in contrast, is often the last stage in the treatment process. After flowing through the filter, water is chlorinated and stored in the clear water reservoir to allow a sufficient contact time for the chlorine to act.
What is chlorine used for?
But the chlorination can also be used for taste and odor control, iron and manganese removal, and to remove some gases such as ammonia and hydrogen sulfide. Chlorination is currently the most frequently used form of disinfection in the water treatment field. However, other disinfection processes have been developed. Like several other water treatment processes, chlorination can be used as a pretreatment process (pre-chlorination) or as the final treatment of water (post -chlorination).
What is the term for adding chlorine to water after the break point?
The addition of chlorine beyond break point is called break point chlorination . The residual of free chlorine, appearing after break point, is not usually removed except by sun light and therefore, it takes care of the future recontamination of water.
What is pre chlorine?
Pre-chlorination is the addition of chlorine to the raw water prior to treatment to produce residual chlorine after meeting chlorine demand. The residual chlorine is useful in several stages of the reatment process – aiding in coagulation, controlling algae problems in sedimentation basins, reducing odor problems, and controlling mud-ball formation in filters. In addition, the chlorine has a much longer contact time when added at the beginning of the treatment process, so prechlorination increases safety in disinfecting heavily contaminated water.
What is post chlorination?
Post chlorination is the normal process of applying chlorine in the end, when all other treatments are completed but before the water reaches the distribution system. At this stage, chlorination is meant to kill pathogens and to provide a chlorine residual in the distribution system.
What does de chlorine mean?
De-chlorination means removing the chlorine from the water. This is generally required when super-chlorination has been practiced. The de-chlorination process may either be carried out to such an extent that sufficient residual chlorine of 0.1 to 0.2 mg/L only remains in water after de-chlorination.
Why is pre chlorination always followed by post chlorination?
The pre-chlorination is always followed by post chlorination, so as to ensure final safety of water. Until the middle of the 1970s, water treatment plants typically used both pre-chlorination and post-chlorination.
