__NOTOC__[[Image:Icon boiling1.png|right|80px|]][[Image:boiling water.jpg|thumb|right|200px|Boiling water for purification. <br>Photo: [https://kopernik.info/ Kopernick]]] Boiling is considered the world’s oldest, most common, and one of the most effective methods for treating water. If done properly, boiling kills or deactivates all bacteria, viruses, protozoa (including cysts) and helminths that cause diarrheal disease. Pathogens are killed when the temperature reaches 100 degrees Celsius. In high-lying areas, where the boiling temperature of water can be as low as 80 degrees Celcius, a longer boiling time is necessary to kill all pathogens. Organizations recommend boiling both for water treatment in developing countries and to provide safe drinking water in emergency situations throughout the world. Although boiling time recommendations vary significantly, from 0-20 minutes, to make water safe for consumption the water simply must reach the boiling point of 100°C. However, studies in developing countries have documented incomplete inactivation of bacteria in boiled water. This disparity between the laboratory and field results is attributed to users not heating the water to the boiling point and/or recontamination of boiled water in storage. To date, there have been no peer reviewed studies assessing the health impact associated with boiling water, although some case-control studies in cholera outbreaks have noted boiling as being protective against cholera. ===Suitable conditions===Boiling is applicable in area with a good fuel supply, a cultural tradition of boiling, and where water is stored safely after boiling. {| border="1" cellpadding="5" cellspacing="0" align="center"|-! width="50%" style="background:#efefef;" | Advantages! style="background:#f0f8ff;" | Disadvantages|-| valign="top" | - Simple <br>- Uses common knowledge <br>- Gernerally uses locally available materials <br>- Proven inactivation of all bacteria, viruses and protozoa, even in turbid or contaminated water<br>- Socio-cultural acceptance of boiling for water treatment, particularly in tea-consuming cultures<br>- Easy and very effective<br>| valign="top" | - Inefficient <br>- Requires a considerable amount of energy (wood, charcoal, fuel) <br>- Time consuming<br>- Does not remove suspended or dissolved compounds <br>- Lack of residual protection against contamination<br>- Potential for burn injuries<br>- Potentially high cost of carbon-based fuel source (with concurrent deforestation risk) and the opportunity cost of collecting fuel<br>- Potential user taste objections<br>- Potential for incomplete water treatment if users do not bring water to full boiling temperature<br>- Indoor pollution: increased risk of respiratory infections from indoor stoves or fires<br>- After boiling, water needs cooling down (cannot be consumed immediately)<br>- Deforestation (approx. 1 kg wood/1 litre water)<br>- CO2 emission<br>|}
{{Potential_Treatment_Capacity_table
- Helminths<br>
| somewhat=
- Ca,
- Mg
| not=
- TurbidityTSS<br>- Taste, odour, colourTDS<br>- Dissolved Chemicals| process=DesinfectionThermal disinfection
| watcrit=Any water can be boiled
}}
===Construction, operations and maintenance===
[[Image:CAWST_Biosandvillage boiling.pngjpg|thumb|right|150px200px| Cross-section through a concrete biosand filterSeveral solar cookers at work boiling water to make it safe to drink. Photo: [http://climate.nasa.gov/kids/games/solaroven/index.cfm Nasa.gov]]]
==What is boiling?==Boiling is considered the world’s oldest, most common, and one of the most effective methods for treating water. If done properly, boiling kills or deactivates all bacteria, viruses, protozoa (including cysts) and helminths that cause diarrheal disease. Operation====
==How Does It Remove Contamination?==Pathogens are killed when the temperature reaches 100 degrees CelsiusWater is heated over a fire or stove until it boils. In high-lying areas, where the boiling temperature of water Different fuel sources can be used depending on local availability and cost (e.g. wood, charcoal, biomass, biogas, kerosene, propane, solar panels, electricity). Water bubbling as low as 80 degrees Celcius, it boils provides an easy to recognize visual indicator and does not need a longer boiling time is necessary to kill all pathogenstemperature gauge.
==Operation==Water is Recommended boiling times vary between organizations. The World Health Organization recommends that water be heated over a fire or stove until it boils. Different fuel sources can be used depending on local availability and cost reaches the boiling point (eWHO<ref>[[#WHO|WHO]]</ref>).g. woodIf the boiling point is reached, charcoalboiling is effective at inactivating all the bacteria, biomassviruses, biogasand protozoa that cause diarrheal disease. The Centers for Disease Control and Prevention, kerosenerecommends a rolling boil of 1 minute, propane, solar panelsto ensure that users do not stop heating the water before the true boiling point is reached (CDC, electricity2009).
CAWST<ref>[http://www.cawst.org Centre for Affordable Water bubbling as it boils provides an easy to recognize visual indicator and does not need a temperature gaugeSanitation Technology]</ref> recommends boiling water for 1 minute and adding 1 minute per 1000 metres of elevation.
Recommended boiling times vary between organizationsRecontamination of boiled water is a major problem. The World Health Organization recommends that water Water is often transferred from the pot into dirty storage containers which then make it unsafe to drink. Water should be heated until stored in the same container in which it reaches the boiling point (WHO<ref>[[#WHO|WHO]]</ref>). The Centers for Disease Control and Preventionwas boiled, recommends a rolling boil of 1 minutehandled carefully, and consumed within 24 hours to ensure that users do not stop heating the water before the true boiling point is reached (CDC, 2009)prevent recontamination.
CAWST<ref>[http://wwwSome people believe that boiled water tastes flat.cawstThis is caused by dissolved oxygen escaping from the water as it boils.org Centre for Affordable Water and Sanitation Technology]</ref> recommends boiling This can be reduced by vigorously stirring or shaking cooled water for 1 minute and adding 1 minute per 1000 metres of elevationto increase its dissolved oxygen content.
Recontamination of boiled water is a major problem. Water is often transferred from Almost all households have the pot into dirty storage containers which then make it unsafe to drink. It is recommended equipment required to store boiled boil water in its pot with a lid to reduce the risk of recontamination.
Some people believe that boiled water tastes flat====Manufacturing====Needed materials are fuel (e. This g. wood, charcoal, biomass, biogas, kerosene, propane, solar panels, electricity, a pot and a lid. Labour is caused by dissolved oxygen escaping from needed for the water as it boilsregular collection of some fuels (e.g. This can be reduced by vigorously stirring or shaking cooled water to increase its dissolved oxygen contentwood, charcoal, biomass).
There is potential for burn injuries; caution should be maintained around stoves and fires and when handling hot water. Cause of respiratory infections associated with poor indoor air quality; improved stoves can be used to reduce illness and death from indoor fires and stoves.
====Treatment efficiencyEfficiency====
{{Treatment_Efficiency
|lab:bacteria=Up to 100%
}}
==Operating criteria==Pathogens are killed when the temperature reaches 100 degrees Celsius. Boil water for 1 minute and add 1 minute per 1000 metres of elevation. Boiled water should be kept in the pot covered with a lid until it is consumed. ==Robustness==Almost all households have the equipment required to boil water. Boiling requires fuel supply and takes time. Users may not consistently boil water to conserve fuel and save time. Maintenance==Estimated lifespan==On-going requirement for fuel. Pots used for boiling need may need replacement. =====Materials and facilities=====Needed materials are fuel (e.g. wood, charcoal, biomass, biogas, kerosene, propane, solar panels, electricity, a pot and a lid. =====Labour=====Regular collection of some fuels (e.gto be replaced. wood, charcoal, biomass)
===Costs==Hazards=====* Potential for burn injuries; caution should be maintained around stoves and fires and when handling hot water* Cause of respiratory infections associated with poor indoor air quality; improved stoves can be used to reduce illness and death from indoor fires and stoves
==Cost==
{{Treatment_Cost
|CapCost=US$ 0*
Note: Program, transportation and education costs are not included.
==External =Manuals, videos, and links===* [http://www.cawst.org/assets/File/HWTS_Fact_Sheet_Boiling.pdf Household Water Treatment and Safe Storage, Fact Sheet 4.1: BOILING]. Provided by: [http://www.cawst.org CAWST (Centre for Affordable Water and Sanitation Technology)]
==Footnotes=References===
<references/>
==References=Acknowledgements===*<cite>Centers This article is based on a factsheet from [http://www.cawst.org/ Centre for Disease Control Affordable Water and Prevention Sanitation Technology (2009CAWST)], which is gratefully acknowledged. * Household Water Treatment Options in Developing Countries: Boiling. Centers for Disease Control and Prevention (2009). Atlanta, USA.</cite>
*<cite id=clasen07>Clasen, T. (2007)[http://citeseerx.ist.psu. edu/viewdoc/download?doi=10.1.1.485.2145&rep=rep1&type=pdf Microbiological effectiveness Effectiveness and cost Cost of boiling to disinfect drinking water: Case studies from Vietnam and Disinfecting Water by Boiling in Semi-urban India]. (Presentation) London School of Hygiene and Tropical Medicine, 2008.</cite>
*<cite id=clasenetal07>Clasen, T., Thao, D., Boisson, S., and Shipin, Oet al. [http://www.ncbi.nlm.nih. (2008) gov/pubmed/18605541 Microbiological effectiveness and cost of boiling to disinfect drinking water in rural Vietnam]. Environmental Science and Technology; 42(12): 42:55.</cite>2008.
*<cite id=WHO>World Health Organization. [http://www.who.int/entity/household_water/resources/emergencies.pdf Household Water Treatment and Safe Storage Following Emergencies and Disasters: South Asia Earthquake and Tsunami]. Available at: [wwwWorld Health Organization.who.int/household_water/en/]</cite>
