__NOTOC__[[Image:safe_water_systems_icon.png|right|80px]][[Image:chlorine disinfection.jpg|thumb|right|200px|A women using chlorine to disinfect water]]Sodium hypochlorite is one form of chlorine used for water disinfection. It can be manufactured in most locations since it can be obtained through the electrolysis of salt water. Bottles can be purchased for household water treatment from many manufacturers in various sizes. Chlorine concentrations range from 0.5 to 10% and each product should have its own instructions for correct dosing of contaminated water. Liquid household bleach also contains sodium hypochlorite, and is widely available. Chlorine forms hydrochloric acid when added to water which causes chemical reactions which deactivate contaminants and reacts through oxidization with micro-organisms, organic matter, manganese, iron and hydrogen sulphide. '''Three things can happen when chlorine is added to water:''' #Some chlorine reacts through oxidization with organic matter and the pathogens in the water and kills them. This portion is called consumed chlorine.#Some chlorine reacts with other organic matter and forms new chlorine compounds. This portion is called combined chlorine.#Excess chlorine that is not consumed or combined remains in the water. This portion is called free residual chlorine (FRC). The FRC helps prevent recontamination of the treated water. Chlorine began to be widely used as a disinfectant in the early 1900’s. It revolutionized drinking water treatment and dramatically reduced the incidence of waterborne diseases. Chlorine remains the most widely used chemical for water disinfection in the United States. ===Suitable conditions===Unlimited amounts of water can be processed at a time, depending on the amount of active chlorine. Some users complain about the taste and odour that chlorine may cause in water. Chlorine reacts with organic matter naturally present in water to form by-products such as trihalomethanes (THMs), which are potentially cancer-causing. Lantagne et al. (2008)<ref>[[#lantagne08|Lantagne et al. (2008)]]</ref> indicate that THM levels produced during household chlorination may fall below World Health Organization (WHO) guideline values. The use of household bleach products for household water treatment is not recommended in the absence of ongoing quality control testing, due to poor quality control of most sodium hypochlorite bleaches. If household bleach is used, the concentration should be regularly tested and an appropriate dosage strategy (2 mg/l for waters of turbidity 0-10 NTU, 4 mg/L for water of turbidity 10-100 NTU) should be developed by the recommending organization. {| border="1" cellpadding="5" cellspacing="0" align="center"|-! width="50%" style="background:#efefef;" | Advantages! style="background:#f0f8ff;" | Disadvantages|-| valign="top" | - Inexpensive <br>- Kills bacteria nad viruses effectively <br>- Residual chlorine protects water from recontamination <br>- Acceptability to users because of ease-of-use <br>- Proven health impact <br>- Scalability <br>- Low cost <br>- Plenty of testing and field assessments <br>- Local familiarity with product <br>| valign="top" | - Lower disinfection effectiveness in turbid waters contaminated with organic and some inorganic compounds <br>- May not be effective at killing parasites <br>- Taste and odor are unacceptable to some <br>- Chlorine forms complex compounds with organic material which may be detrimental to health over time. <br>- Chlorine degrades over time. <br>- Contact time is required. <br> - Most users cannot determine the dosing quantity themselves; proper use requires simple instructions from the manufacturer <br>- Chemical dosage required varies with water quality<br>- Chlorine needs to be purchased continuously <br>- Chlorine can be hazardous if used improperly. Requires quality control process to ensure product reliability - Chlorine fumes and contact with skin are hazardous <br>- Concern about the potential long-term carcinogenic effects chlorination by-products <br>- Relatively short shelf life <br>- Uncertain concentration and shelf life, susceptibility to gaps in supply chain, high transportation costs, and difficulty in dispensing precise quantities <br>|}
{{Potential_Treatment_Capacity_table
- Viruses<br>
- Most Protozoa<br>
- Helminths<br>- Ammonium <br>
| not=
- Cryptosporidium oocysts<br>
- Chemicals<br>
- Taste, odour, color
| process=DisinfectionChemical disinfection
| watcrit=
Low Turbidity<br>
}}
==What is a Sodium hypochlorite?=Construction, operations and maintenance===Chlorine began There are several different brands of chlorine products that have been manufactured specifically for household water treatment. Each product should have its own instructions for correct dosing and contact time. Liquid household bleach products are also commonly used to disinfect drinking water. The strength of the product must be widely used as known to calculate how much bleach is needed to disinfect a disinfectant in given amount of water. Commercial bleach from the early 1900’sUnited States requires users to add 3-5 drops to 5 gallons of water. It revolutionized drinking Some bleach bottles come with a top that dispenses by drops The effectiveness of chlorine is affected by turbidity, organic matter, temperature and pH. For high turbidity levels, the water treatment should first be strained through a cloth or sedimented before adding chlorine. These processes will remove some of the suspended particles and dramatically reduced improve the incidence of waterborne diseasesreaction between the chlorine and pathogens. Chlorine remains the most widely used chemical The manufacturer’s instructions for specific sodium hypochlorite products need to be followed. The required dose and contact time varies with water disinfection in the United Statesquality (e.g. turbidity, pH, temperature).
Sodium hypochlorite Use a 30 minute minimum contact time. If the pH is one form above 7.5, a higher FRC concentration of chlorine used for water disinfection0. It can 6 mg/litre should be manufactured in most locations since it can be obtained through used and the electrolysis of salt water. Bottles can contact time should be purchased for household water treatment from many manufacturers in various sizes. Chlorine concentrations range from 0.5 extended to 10% and each product should have its own instructions for correct dosing of contaminated water. Liquid household bleach also contains sodium hypochlorite, and is widely available1 hour.
==How Does The contact time should be increased to 1 hour when the temperature is between 10˚ and 18˚C. It Remove Contamination?==should be increased to two or more hours when the temperature falls below 10˚C.<!--See CAWST’s Technical Brief on Chlorine forms hydrochloric acid when added Disinfection of Drinking Water for information on how to water which reacts through oxidization with micro-organisms determine the chlorine dose and kills themcontact time using household bleach. -->
Three things Metering pumps as [[Dosatron]] can happen when chlorine is added to water:be used for proportional dosing .
#Some chlorine reacts through oxidization with organic matter and the pathogens in the water and kills them. This portion is called consumed chlorine.#Some chlorine reacts with other organic matter and forms new chlorine compounds. This portion is called combined chlorine.====Manufacturing====#Excess chlorine that is not consumed or combined remains It can be manufactured in most locations since it can be obtained through the waterelectrolysis of brine. This portion is called free residual chlorine (FRC). The FRC helps prevent recontamination of the treated Bottles can be purchased for household water.treatment from many manufacturers in various sizes
==Operation==There are several different brands of chlorine products that have been manufactured specifically Hypochlorite solution for household water treatmentcan be manufactured in four ways, in order of decreasing quality control: 1) chlorine gas injection into a stream of water, 2) dilution of higher concentration sodium hypochlorite solution, 3) dilution of calcium hypochlorite powder; and, 4) electrolytic generation of sodium hypochlorite from salt, water, and electricity. Each product In all cases: 1) distilled or deionized water should have its own instructions be used for correct dosing manufacturing; 2) the solution should be stabilized to pH over 11,9 to ensure adequate shelf- life of a minimum of 12 months; and, 3) each batch should be tested for chlorine concentration and contact timepH. For national scale programs, it is recommended to work with a local company to manufacture the solution using high-quality processes
Liquid household bleach products are also commonly Skin and eye protection should be used to disinfect drinking waterwhen handling chlorine solutions. The strength of the product must Work should be known to calculate how much bleach is needed to disinfect conducted in a given amount of waterwell ventilated area or in the open air. <!--See CAWST’s Technical Brief on Chlorine Disinfection of Drinking Water for information on how Trained workers needed to determine produce and test the chlorine dose and contact time using household bleachsodium hypochlorite.-->
The effectiveness ====Treatment Efficiency====With the appropriate dose, disinfection with chlorine will kill 100% of chlorine bacteria and viruses, but is affected by turbidity, organic matternot efficient enough to inactivate pathogenic parasites (e.g. Giardia, temperature Cryptosporidium and pHhelminths eggs).
For high turbidity levels, A recent meta-analysis showed that chlorine reduces the water should first be strained through a cloth or sedimented before adding chlorine. These processes will remove some risk of the suspended particles and improve the reaction between the chlorine and pathogens.child diarrhea by 29%
==Treatment efficiency=={| border="1" cellpadding="5" cellspacing="0" align="centernone"
|-
! style="background:#efefef;" |
| valign="top" | moderate<ref name=cdcp07/>
| valign="top" | high<ref name=cdcp07/>
| valign="top" | not availablehigh
|}
Toxoplasma oocysts and cryptosporidium oocysts are highly resistant to chlorine disinfection <ref name=cdcp07/>). Chlorine alone should not be expected to inactivate these pathogens in drinking water.
==Operating criteria==Maintenance====*'''Flow rate:''' Not applicable*'''Batch volume:''' Unlimited*'''Daily water supply:''' Unlimited The manufacturer’s instructions for specific sodium hypochlorite products need to be followedFree residual chlorine protects against recontamination. The required dose and contact time varies with water quality (e.g. turbidity, pH, temperature). Use a 30 minute minimum contact time. If Most users cannot determine the pH is above 7.5, a higher FRC concentration of 0.6 mg/litre should be used and dosing quantity themselves; proper use requires simple instructions from the contact time should be extended to 1 hourmanufacturer. The contact time should be increased to 1 hour when Users often use less than the temperature is between 10˚ and 18˚C. It should be increased recommended dose to two or more hours when the temperature falls below 10˚C. <!--See CAWST’s Technical Brief on Chlorine Disinfection of Drinking Water for information on how to determine the chlorine dose and contact time using household bleachsave money. -->
==Robustness==Free residual chlorine protects against recontaminationChlorine requires a supply chain, market availability and regular purchase. Most users cannot determine the dosing quantity themselves; proper use It also requires simple instructions from the manufacturerquality control process to ensure product reliability. Users often use less than the recommended dose Sourcing suitable plastic containers to save moneymanufacture chlorine solutions can sometimes be a challenge.
Chlorine requires should be stored in a supply chaincool, market availability and regular purchase. It also requires quality control process to ensure product reliability. Sourcing suitable plastic containers to manufacture chlorine solutions can sometimes be dark place in a challengeclosed container.
====Estimated lifespanLifespan====
Chlorine deteriorates over time, especially in liquid form. Liquid chlorine products should be used within 3 months of being manufactured.
==Manufacturing requirements== =====Worldwide producers=Suppliers====There are many producers of chlorine solutions all around the world. <!--See CAWST’s Sodium Hypochlorite Product Sheets for further details.--> =====Local production=====Can be made locally using salt water solution and electrolysis equipment. =====Materials and facilities=====* Generator with electrolysis equipment* Plastic bottles and labelling equipment* Salt* Water =====Fabrication Facilities=====Workshop space is required for chlorine production and bottling. Good ventilation required in the workshop space.
===Costs==Labour=====Trained workers needed to produce and test the sodium hypochlorite. =====Hazards=====Chlorine fumes and contact with skin are hazardous. Skin and eye protection should be used when handling chlorine solutions. Work should be conducted in a well ventilated area or in the open air. ==Maintenance requirements==Chlorine should be stored in a cool, dark place in a closed container. ==Cost==
{{Treatment_Cost
|CapCost=US$ 0
Note: Program, transportation and education costs are not included.
==Other=Field Experiences===Some users complain about the taste and odour that The following project(s) utilize chlorine may cause in water. Chlorine reacts with organic matter naturally present in water to form by<br>{|style="border: 2px solid #e0e0e0; width: 20%; text-align: justify; background-color: #e9f5fd;" cellpadding="2"|- style="vertical-align: top"|[[Image:akvorsr logo_lite.png|center|60px|link=http://akvo.org/products such as trihalomethanes (THMs), which are potentially cancer/rsr/]]|- style="vertical-causingalign: bottom"|[[Image:project 810. Lantagne et al. (2008)png |thumb|center|140px|<font size="2"><refcenter>[[#lantagne08|Lantagne et alhttp://wash-liberia.akvoapp. (2008)]org/en/project/810/ RSR Project 810]<br>Improved Water Sanitation and Hygiene</center></reffont> indicate that THM levels produced during household chlorination may fall below World Health Organization (WHO) guideline values|link=http://wash-liberia.akvoapp. org/en/project/810/ ]] |}
==Movies==<br>
==External =Manuals, videos, and links===* [http://fieldresearch.msf.org/msf/bitstream/10144/618835/1/FRC+Op+Guidance+Briefing+Note+%28Nov+2016%29.pdf Operational Guidance Briefing Note: Evidence-based Free Residual Chlorine (FRC) Targets]
*[http://www.cawst.org CAWST (Centre for Affordable Water and Sanitation Technology)]
*[http://www.enpho.org/drinking_water_quality.htm Drinking water quality information from Environment and Public Health Organization (ENPHO)]*[httphttps://www.cdc.gov/safewater/publications_pages/pubs_chlorinechlorination.htm html Centers for Disease Control and Prevention]
*[http://www.psi.org/child-survival Population Services International (PSI)]
*[[Solution_of_the_week_3|Akvo water solution of the week 3]]
===References===<references/> ===Acknowledgements===
This article is based on a factsheet from [http://www.cawst.org/ Centre for Affordable Water and Sanitation Technology (CAWST)], which is gratefully acknowledged.
==Footnotes==
<references/>
==References==
* <cite id=CDCP07>Centers for Disease Control and Prevention (CDC 2007). Effect of Chlorination on Inactivating Selected Pathogens. Available at:www.cdc.gov/safewater/about_pages/chlorinationtable.htm </cite>
* <cite id=Lantagne08>Lantagne, D.S., Blount, B. C., Cardinali, F., and R. Quick (2008). Disinfection by-product formation and mitigation strategies in point-of-use chlorination of turbid and non-turbid waters in western Kenya. Journal of Water and Health, 06.1, 2008.</cite>
* <cite id=luby01>Luby, S., Agboatwalla, M., Razz, A. and J. Sobel (2001). A Low-Cost Intervention for Cleaner Drinking Water in Karachi, Pakistan. International Journal of Infectious Diseases; 5(3): 144-150.</cite>Cambodia.</cite>
