How does chlorination work in wastewater treatment?
Nearly every wastewater treatment facility uses chlorination to disinfect wastewater before the water is sent back out into the environment. The primary goal of chlorination is to disinfect the wastewater and remove any harmful pathogens that are present in the water.
What type of chlorine is used in water treatment plants?
The two most common forms of chlorine used in the treatment plants are liquid chlorine stored under pressure in cylinders and sodium hypochlorite which is strong bleach. When liquid chlorine is used, it is added as a gas. Either the gas is taken from the top of the cylinder or the liquid is passed through a hot water bath to heat it to a gas.
What is chlorination and why is it important?
The primary goal of chlorination is to disinfect the wastewater and remove any harmful pathogens that are present in the water. Once the wastewater has been properly treated, it can flow naturally into rivers, streams, and oceans without issue.
What is chlorination equipment?
Equipment Chlorination equipment consists of various components. The gas system consists of equipment that allows for the safe removal of chlorine from a vessel, and transmission through a series of valves, piping and control devices, under vacuum to a point of application. A schematic of a typical gas feed system is shown in Figure 4.1.
What is chlorine used for in wastewater treatment?
Chlorine is the most widely used disinfectant for municipal wastewater because it destroys target organisms by oxidizing cellular material. Chlorine can be supplied in many forms, which include chlorine gas, hypochlorite solutions, and other chlorine compounds in solid or liquid form.
Why is chlorine added to waste water?
Chlorine is added to raw water to eliminate algae and other forms of aquatic life from the water so they won't cause problems in the later stages of water treatment.
Where is chlorine used in water treatment?
The most common use of chlorine in water treatment is to disinfect water. As a disinfectant, it has drawbacks, but it also has advantages. Other methods of disinfection such as ultraviolet and ozonation are effective disinfectants but they do not provide a residual to prevent pathogen regrowth as chlorination does.
Why does most wastewater treatment involve chlorination?
Chlorine is fed into the water to kill pathogenic bacteria, and to reduce odor. Done properly, chlorination will kill more than 99 percent of the harmful bacteria in an effluent.
What is the advantage 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.
Does chlorine reduce bod?
BOD reduction: Chlorine accomplishes BOD reduction by oxidation of organic compounds present in wastewaters. 4. Oxidation of metal ions: Metal ions which are in reduced state are oxidized by chlorine (e.g., ferrous to ferric ion and manganous to manganic ions).
How does chlorination purify water?
Chlorine kills pathogens such as bacteria and viruses by breaking the chemical bonds in their molecules. Disinfectants that are used for this purpose consist of chlorine compounds which can exchange atoms with other compounds, such as enzymes in bacteria and other cells.
How does chlorination system work?
Saltwater Chlorinators use an electrolytic cell to sanitise your swimming pool. By adding a small amount of salt (sodium chloride) to your pool water, the cell converts the chloride contained in the saltwater into chlorine. This is an extremely efficient and cost-effective method of sanitising your pool.
What do you mean by chlorination?
chlorinate. / (ˈklɔːrɪˌneɪt) / verb (tr) to combine or treat (a substance) with chlorine. to disinfect (water) with chlorine.
What is chlorination very short answer?
Chlorination is the process of adding chlorine to drinking water to disinfect it and kill germs. Different processes can be used to achieve safe levels of chlorine in drinking water. Chlorine is available as compressed elemental gas, sodium hypochlorite solution (NaOCl) or solid calcium hypochlorite (Ca(OCl)2.
Chlorination
The STP treats the wastewater coming from agriculture, sewage and industrial plants. The treatment process has four stages (pretreatment, primary, secondary and tertiary treatment).
Chlorine Compounds as Disinfectant
We can add chlorine into the tertiary system via chemical feed inlets. Three standard formulations of chlorine are available for chlorination:
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 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.
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 chlorine used for?
Chlorine is a powerful oxidizer that is commonly used in wastewater treatment for disinfection and odor control, bulking control, and other applications. When chlorine is added to a unit process, we want to ensure that a measured amount is added. Chlorine dose depends on two considerations - the chlorine demand and the desired chlorine residual.
How is chlorine dose determined?
It may be determined by adding excess chlorine to water and then by measuring the difference between the added amount of chlorine and the residual chlorine after a specified time period. The chlorine requirement, or chlorine dosage, is the sum of the chlorine demand and the desired chlorine residual.
What are the diseases that are associated with wastewater?
Wastewater contains many types of human enteric organisms that are associated with various waterborne diseases. Typhoid, cholera, paratyphoid, and bacillary dysentery are caused by bacteria, and amebic dysentery is caused by protozoa. Common viral diseases include poliomyelitis and infectious hepatitis. Disinfection refers to selective destruction of disease-causing organisms in the wastewater effluent. The term sterilization denotes the complete destruction of all organisms. Pasteurization is selective destruction of undesired organisms by heat.
Is chlorine a gas?
Chlorine is yellow-green in the gas form and amber colored in liquid form. It is 2.5 times heavier than air, non-flammable and a very strong oxidizing agent. The pressurized containers normally contain approximately 80% liquid chlorine and 20% gas. Although chlorine can be fed directly into the wastewater, most facilities dissolve the chlorine gas in water to reduce safety risks and facilitate movement to the point of application.
Is hypochlorite a substitute for chlorine?
Hypochlorite is less hazardous than chlorine; therefore, it is often used as a substitute chemical for elemental chlorine. Hypochlorite is similar to strong bleach and comes in two forms: dry calcium hypochlorite, often referred to as HTH, and liquid sodium hypochlorite. Calcium hypochlorite contains about 65% available chlorine; sodium hypochlorite contains about 12 to 15% available chlorine, in industrial strengths.
What is the purpose of chlorination in wastewater treatment?
Chlorination, which follows all other steps of treatment, reduces the population of organisms in the wastewater to levels low enough to ensure that pathogenic organisms will not be present in sufficient quantities to cause disease when the wastewater is discharged.
Why is dechlorination needed in wastewater?
Dechlorination. Chlorine needs to be put into wastewater to treat it and oxidize any contaminants it once held when in the sewage system. The chlorination wastewater treatment procedure creates byproducts in treated water. Dechlorination involves removing any chlorine-based byproducts to ensure the water is truly safe.
What is dechlorination in chemistry?
Dechlorination is the process of removing the free and combined chlorine residuals to reduce residual toxicity after chlorination and before discharge. Sulfur dioxide, sodium bisulfite, and sodium metabisulfite are the commonly used dechlorinating chemicals. Activated carbon has also been used.
What is the term for selective destruction of disease-causing organisms in the water supply or in wastewater effluent
Disinfection refers to selective destruction of disease-causing organisms in the water supply or in wastewater effluent. Wastewater, after secondary treatment to remove BOD and solids, may still contain large numbers of microorganisms.
What are the organisms that are in domestic wastewater?
The organisms of concern in domestic wastewater include enteric bacteria, viruses, and protozoan cysts. In response to these concerns, disinfection has become one of the primary mechanisms for the inactivation/destruction of pathogenic organisms.
What are the chemicals used in dechlorination?
Generally, the most common chemicals used for dechlorination are sulfur dioxide, sodium bisulfate, sodium sulfite, sodium thiosulfate and activated carbon. The chemical equivalents required for dechlorination can be calculated, however, laboratory experiments should be used to help to define the required dose.
What is wastewatr?
Control of Waterborne Diseases. As mentioned, wastewatr contains many types of human enteric organisms that are associated with various waterborne diseases. Typhoid, cholera, paratyphoid, and bacillary dysentery are caused by bacteria and amebic dysentery is caused by protozoa. Disinfection refers to selective destruction ...
Why is it important to remove chlorine from water?
It is important to remove chlorine because wastewater effluent is discharged into streams, rivers, and lakes, which provide habitat for wildlife and plant life. Without dechlorination, excess chlorine may kill the wildlife and plant life. Dechlorination of plant effluent flow may be accomplished by various processes.
Why do you need to dechlorinate after disinfection?
The effluent from a wastewater treatment plant may need to be dechlorinated after disinfection because of harmful affects the chlorine residual may have on fish, wildlife , and even human health.
What is the demand for chlorine?
The demand by inorganic and organic materials is referred to as the chlorine demand. It is the difference between the amount of chlorine applied to the wastewater and the amount of residual chlorine after a given contact time.
What is the most commonly used disinfection process for wastewater treatment?
Chlorine and its various forms are powerful oxidants that will kill or inactivate most pathogenic organism that are harmful to human and animal life. Chlorination is the most commonly used disinfection process for wastewater treatment.
What is chlorine residual?
It is the component of the applied chlorine that is available for disinfection. The residual is available in three forms:
How is chlorine dioxide generated?
Due to its instability, chlorine dioxide is generated on site and used within a short period of time after generation. Two systems are used to generate the chemical. In each, the process blends chlorinated water or hydrochloric acid with sodium chlorite in a mixing chamber to produce chlorine dioxide. The reactions are as follows:
How much chlorine is in a cylinder?
Elemental chlorine is provided in liquid form and delivered in 150-pound cylinders and 1-ton containers.
