Fecal pathogens in the environment can contaminate water through multiple pathways, including fingers, flies, fomites, and drainage. When anyone drinks contaminated water or uses it to prepare food or complete other household tasks, it can cause intestinal infections, inflammation of the gut, or micronutrient deficiencies by reducing micronutrient absorption. While using a safely managed source of drinking water makes contamination less likely, the type of infrastructure used as a water source and the water’s microbiological safety do not correlate perfectly. Unless the drinking water source is under an effective water quality surveillance and regulatory regime, the water may need additional treatment measures to make it microbiologically safe for consumption. Water quality typically declines from the source to consumption, due to multiple opportunities for contamination during collection, transport, storage, and use in the household. Therefore, consider the entire chain of water quality—from source to safe storage. Contamination of water is likely during transport, handling, and storage within households, and it calls for point-of-use water treatment.
Evidence-based drinking water treatment options include—
- filtration through a certified filter (ceramic, membrane, or biosand) that has been tested for pathogen removal efficiency; filters will clarify turbid water but, typically, do not remove 100 percent of the pathogens; it requires a second step of disinfection—usually filtration plus chlorination—to ensure safe drinking water
- chemical disinfection—typically with chlorine or iodine
- boiling to disinfect, combined with a strong behavioral component to prevent recontamination of the treated water
- thermal treatment with solar radiation
- solar treatment by ultraviolet and thermal effects
- lamps to disinfect
- alum and iron coagulation
- charcoal and activated carbon adsorption
- iron exchange to disinfect
- combination of flocculation and disinfection (e.g., purifier of water) (Agrawal and Bhalwar 2009).
The best treatment option depends on the cultural context, organoleptic (taste and smell) expectations, as well as the efficacy; but all also require safe management, including safe storage in a narrow-mouthed container with a lid and a tap to prevent recontamination.
Measurement and data sources
Multiple options are available for measuring water treatment (WHO 2012), including reported use of a treatment option, observation of the correct use of the treatment method in the household, or conducting water quality tests to compare treated and untreated water—by looking at reductions in bacteria—or to test for the presence of chlorine.
Surveys generally report the percentage of households (or household members) using an appropriate treatment method; some surveys specify that the treatment must take place prior to drinking. Generally, households participating in a survey or data collection activity are asked to describe what they do to make their water safe to drink. “Appropriate method” in standard survey reports includes boiling, adding bleach or chlorine, filtering, and solar disinfecting.
Surveys that collect information related to water treatment methods include—
- Demographic and Health Surveys
- Multiple Indicator Cluster Surveys
- National Micronutrient Surveys
- Knowledge, Practice, and Coverage Surveys
- other research or evaluation activities.
The WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation maintains a database of information on coverage of water, sanitation, and hygiene programs.
- Collecting data by observing household treatment practices, or conducting water quality tests, is expensive, may be impractical, and may change the behavior of the people being observed.
- Some reports or surveys may restrict questions or findings on water treatment to households that do not report using a basic water source; verify which populations are included in the data you collect.
- Some surveys include options that do not have an evidence base for reducing diarrhea in children under 5, for example “filtering water through a cloth.” Ensure that any analysis includes only the evidence-based treatment methods listed above.
Agrawal, COL, and Brig Bhalwar. 2009. “Household Water Purification: Low-Cost Interventions.” Medical Journal Armed Forces India 65: 260–63.
Dodos, Jovana. 2017. “WASH’Nutrition: A Practical Guidebook on Increasing Nutritional Impact through Integration of WASH and Nutrition Programmes.” Paris; France: ACF International. http://www.actioncontrelafaim.org/fr/content/wash-nutrition-practical-gu....
Sobsey, Mark D. 2002. Managing Water in the Home: Accelerated Health Gains from Improved Water Supply. Geneva, Switzerland: WHO.
WHO. 2012. A Toolkit for Monitoring and Evaluating Household Water Treatment and Safe Storage Programmes. Geneva: World Health Organization.
———. 2015. Improving Nutrition Outcomes with Better Water, Sanitation and Hygiene. Geneva, Switzerland: WHO.