EHP Library Hygiene Bulletin
|No. 14, September 26, 2002|
In This Issue
Managing Water in the Home: Accelerated Health Gains from Improved Water Supply, 2002. WHO, 2002.
The final version of this report is now available in html and pdf formats. Click on the title above to link to the report.
The purpose of this report is to critically review the various candidate technologies and systems for providing microbiologically improved household water and to identify the most promising ones based on their technical characteristics and performance criteria. The characteristics and performance criteria for these are: effectiveness in improving and maintaining microbial water quality, reducing waterborne infectious disease, technical difficulty or simplicity, accessibility, cost, socio-cultural acceptability, sustainability and potential for dissemination.
This critical review considers methods and systems to protect water during storage, collection and use that improve microbial quality and thereby reduce pathogen exposure and risks of diarrheal and other waterborne diseases. Because it has been repeatedly demonstrated and is generally accepted that the most important and immediate risks to human health from using contaminated drinking water are those from enteric microbes of fecal origin or other sources, this review focuses on strategies and systems to protect and improve the microbiological quality of household water to prevent and control waterborne microbial diseases.
Systems for Household Storage of Collected Water to Protect Microbiological Quality
A review of the existing literature on collection and storage of household water revealed that such water often comes from fecally contaminated sources and therefore poses infectious disease risks to consumers. Furthermore, regardless of whether or not collected household water is initially of acceptable microbiological quality, it often becomes contaminated with pathogens of fecal origin during transport and storage due to unhygienic storage and handling practices.
Studies show that the use of containers with narrow openings for filling, and dispensing devices such as spouts or taps/spigots, protect the collected water during storage and household use. Many container designs also have handles, are lightweight, are made from durable, UV-resistant plastic and are affixed with a label containing informational/educational on their cleaning and use. Other appropriate containers for safe storage are those in which water can be directly treated by the physical method of solar radiation and then directly stored and dispensed for household use. These improved containers protect stored household water from the introduction of microbial contaminants via contact with hands, dippers, other fecally contaminated vehicles or the intrusion of vectors.
Treatment Technologies to Improve the Microbiological Quality of Household Water
A variety of candidate technologies for treatment of household water have been described and many are widely used in different parts of the world. The technologies to improve the microbial quality of household water and reduce waterborne disease include a number of physical and chemical treatment methods. The physical methods, include boiling, heating (fuel and solar), settling, filtering, exposing to the UV radiation in sunlight, and UV disinfection with lamps. The chemical methods include coagulation-flocculation and precipitation, adsorption, ion exchange and chemical disinfection with germicidal agents (primarily chlorine). Some water treatment and storage systems use chemicals and other media and materials that can not be easily obtained locally at reasonable cost and require relatively complex and expensive systems and procedures to treat the water. Such systems may be too inaccessible, complex and expensive to employ for treatment and storage of household water in some places and settings.
The efficacy of some treatment methods to physically remove particles (turbidity) and microbes or to inactivate microbes in household water has been documented, primarily for indicator bacteria. Some treatment methods, such as boiling, solar disinfection, UV disinfection with lamps, chlorination and the combined treatments of chemical coagulation-filtration and chlorination have been evaluated for reductions of bacteria, viruses and in some cases protozoans. However, the ability of some of these methods to remove or inactivate a wide range of known waterborne pathogens has been inadequately investigated and documented. The differences in the technologies of candidate treatment and water storage systems as well as the differences in the types, sizes and other properties of waterborne microbes that need to be removed or inactivated, have contributed to a lack of documentation of the efficacy of these methods for household treatment and storage of water.
With exception of chlorination and storage in a safe container and solar disinfection "SODIS" UV plus heat), most technologies for household water treatment and storage have not been studied for their ability to reduce diarrheal and other waterborne disease in household use. Such epidemiological studies of an intervention are essential in establishing the performance of the technology as well as its acceptance and sustainability by users.
Several candidate technologies for household water treatment and storage appear to be accessible, simple and economical for use in both the developed and developing countries. Some of these systems have been characterized for microbial efficacy and reduction of waterborne disease, and for community acceptance sustainability and cost recovery. Of the systems now available, the following appear to be the most widespread and promising for further development, characterization, implementation and dissemination:
The performance characteristics, advantages, disadvantages and estimated costs of these most promising technologies for household water treatment to improve microbial quality and reduce diarrheal disease are presented in the report.
Treating turbid water: a special concern
For the most promising household water treatment systems of chlorination with an improved storage vessel, solar disinfection with UV plus heat in clear bottles for sunlight penetration (SODIS), and UV irradiation with lamps, effective treatment of turbid water remains a challenge. This is because microbial reductions are decreased or prevented by turbidity particles that reduce access to target microbes or otherwise protect them from inactivation by other mechanisms. Suspended matter in water reduces the microbiocidal efficacy of chlorine and other chemical disinfectants, and it physically shields microbes from the UV radiation that is present in sunlight and emitted from mercury arc lamps and responsible for much of its disinfection activity. There is a need to investigate, characterize and implement physical and physical-chemical technologies for practical and low cost pre-treatment of treatment of household water prior to chlorination, solar disinfection with UV plus heat and UV disinfection with lamps. Appropriate physical and physical-chemical methods for effective pre-treatment for household water needed to be established, taking into consideration turbid waters of different quality with respect to particle characteristics and their removal efficiencies. In principle, some physical or physical-chemical methods may be highly effective for treatment of stored household water on their own. Pre-treatment technologies for removal of turbidity (suspended matter) from water suitable for such applications potentially include:
These methods will vary in their ability to remove interfering turbidity from water, depending on the nature of the turbidity particles. Especially important in this regard is their size and density. Of the listed methods, slow sand filtration is the least likely to be implementable and sustainable at the household level. This is because the preferred filter designs and installations often are larger and capable of treating more water than needed by individual households and because they require technical skills for maintenance and operation that may not be accepted by individual users.
Need for behavioral, motivational, and economic support
The use of technologies to treat and safely store household water is best accomplished if it is accompanied by or supported with economic incentives and other cost recovery methods and with programs designed to support community participation, education and other efforts to achieve acceptance and sustainability. Where such additional socio-cultural, behavioral and economic components of household water treatment and storage technologies are absent or lacking, successful implementation and sustained use are unlikely to be achieved. The importance of economic analyses and community participation, education and responsibility for household water treatment and safe storage can not be over stressed in future efforts to establish and disseminate this intervention for water sanitation.
Numerous studies have clearly shown that improving the microbiological quality of household water by on-site or point-of-use treatment and safe storage in improved vessels reduces diarrheal and other waterborne diseases in communities and households of developing as well as developed countries. The extent to which improving drinking water quality at the household level reduces diarrheal disease probably depends on a variety of technology-related as well as site-specific environmental and demographic factors that require further investigation, characterization and analyses. Reductions in household diarrheal diseases of 6-90% have been observed, depending on the technology and the exposed population and local conditions.
Further development, refinement, implementation, evaluation and comparison of household water treatment and safe storage technologies is both justified and encouraged.
Greater efforts to disseminate information about household water treatment and storage technologies and their benefits and advantages are merited.
The most promising and accessible of the technologies for household water treatment are filtration with ceramic filters, chlorination with storage in an improved vessel, solar disinfection in clear bottles by the combined action of UV radiation and heat, thermal disinfection (pasteurization) in opaque vessels with sunlight from solar cookers or reflectors and combination systems employing chemical coagulation-flocculation, sedimentation, filtration and chlorination. All of these systems have been shown to dramatically improve the microbiological quality of water. At least two of them, solar disinfection in clear plastic bottles (heat plus UV radiation) and chlorination plus storage in an improved vessel, have been shown in epidemiological studies of the intervention type to significantly reduce diarrheal and other infectious diseases, including cholera. These household water treatment and storage systems are considered the most promising and effective, based on their documented ability to improve the microbiological water and reduce waterborne infectious disease risks.
All of the household water treatment technologies described here have been tested independently and so far none have been tested in combination. Historically and with renewed recent interest, water treatment technology and practice have focused on the use of two or more treatment technologies as a multiple barrier approach. There is considerable interest and potential merit in the use of two or more treatment systems in succession for improved treatment and the creation of multiple barriers. In particular those treatments that provide no residual disinfectant, such as boiling, solar treatment, UV disinfection with lamps and filtration could be followed by chlorination and storage in a protected or improved vessel to prove a multibarrier approach that would result in appreciable microbial reduction, continued protection with a disinfectant residual and storage that is less prone to post-treatment contamination. Research and demonstration of such multibarrier treatment and storage approaches deserve consideration and are recommended as next steps in the development, evaluation and implementation of improved treatment and storage of water at the household level.
The introduction of improved water treatment and storage at the household level, if done effectively, is likely to increase personal and community knowledge and awareness of the importance of water hygiene and sanitation and the benefits to be derived therefrom. It is likely that involvement in preparing and using safe water at the household level results in increased knowledge of water hygiene and sanitation, recognition and appreciation of its contribution to infectious disease prevention and control and improved health. Such awareness of the role of safe drinking water in health promotion and diseased prevention support and facilitate the ultimate goal of providing all of the world's population with community piped water that is accessible, safe and affordable.
Links to Other Online Documents
Trop Med Int Health 2002 Sep;7(9):750-756
Diarrhoea and effects of different water sources, sanitation and hygiene behaviour in East Africa.
Tumwine JK, Thompson J, Katua-Katua M, Mujwajuzi M, Johnstone N, Porras I.
Department of Paediatrics and Child Health, Makerere University Medical School, Kampala, Uganda International Institute of Environment and Development, London, UK Community Management and Training Services, Nairobi, Kenya Institute of Resource Assessment, University of Dar-es-Salaam, Tanzania National Policies Division, Organisation for Economic Cooperation and Development, France.
Apart from Drawers of Water (DOW I) published in 1972, there have been only a handful of publishedstudies on domestic water use and environmental health in East Africa, based on direct observations or other reliable research methods. The objective of this study was to carry out a repeat analysis of domestic water use and environmental health in East Africa based on DOW I. The study was conducted in the same sites as DOW I. Field assistants spent at least 1 day in each household observing and conducting semi-structured interviews. They measured the amount of water collected, recorded the amount of water used in the home, and noted household socio-demographic characteristics, prevalence of diarrhoea, state and use of latrines, sources of water and conditions of use. We surveyed 1015 households in 33 sites in Uganda, Tanzania and Kenya in 1997. From 1967 to 1997, the prevalence of diarrhoea, in the week preceding the survey, increased from 6% to 18% in Kenya and from 16% to 21% in Uganda; it declined slightly in Tanzania (11-8%). Determinants of diarrhoea morbidity included poor hygiene (unsafe disposal of faeces and wastewater), education level of household head, obtaining water from surface sources or wells and per capita water used for cleaning. Hygiene practices are an important complement to improved water and sanitation in reducing diarrhoea morbidity.
Acta Trop 2002 Sep;83(3):223
Ascaris lumbricoides among children in rural communities in the Northern Area, Pakistan: prevalence, intensity, and associated socio-cultural and behavioral risk factors.
Nishiura H, Imai H, Nakao H, Tsukino H, Changazi M, Hussain G, Kuroda Y, Katoh T.
Department of Public Health, School of Medicine, Miyazaki Medical College, 5200 Kihara, Kiyotake, Prefecture 889-1692, Miyazaki, Japan
The prevalence and intensity of Ascaris lumbricoides in 492 children from five rural villages in the Northern Area of Pakistan was examined. The overall prevalence of A. lumbricoides was 91% (95%CI 88.6-93.6) with geometric mean (GM) egg count intensities of 3985 eggs per g (epg). The most intense A. lumbricoides infections were found in children aged 5-8 years. We also investigated selected socio-cultural and behavioral variables for A. lumbricoides infections that might be relevant for the design of appropriate prevention and control programs. Univariate analysis associated A. lumbricoides intensity with age (P=0.004), location of household (P<0.01), defecation practices (P=0.02), soil eating habit (P<0.01), hand washing after defecation (P<0.01), and living with children under 5 years old (P=0.02). Multivariate analysis identified the children's age 5-8 (P<0.01), location of household in Surngo, Askole, and Stakchun where the pilot health care model activities were not done (P<0.01), and living with children under 5 years old (P=0.03) as variables statistically associated with the intensity of A. lumbricoides. The results indicated that there were certain clear risk factors in A. lumbricoides transmission, and that its intensity was influenced by age-related behavioral and environmental factors that contribute to exposure.
J Public Health Med 2002 Jun;24(2):85-7 Related Articles, Links
Standards in school toilets--a questionnaire survey.
Barnes PM, Maddocks A.
Department of Child Health, Swansea NHS Trust, Central Clinic.
BACKGROUND: Children often say they have problems with their toilets in school. Educationalists and health workers need to be aware of potential difficulties, to try and improve these facilities for school children. The objective of this study was to assess the perception children have of the toilet facilities in their schools and whether or not this influences their use of them. METHODS: An interviewer-administered questionnaire was given to children attending community audiology clinics and their parents. RESULTS: Eighty-seven children from 65 schools were surveyed. Poorly maintained and unhygienic facilities were described to which access was restricted. A significant proportion of children were bullied or teased. Forty per cent would never open their bowels using the toilets in school. CONCLUSION: The same standards for toilet facilities in the workplace should apply to schools. Substandard facilities may contribute to the suppression of the 'call to stool', leading to chronic constipation. Infectious illnesses may be more easily spread.
Arch Dis Child 2002 Jul;87(1):30-5
Factors associated with different hygiene practices in the homes of 15 month old infants.
Sherriff A, Golding J; The Alspac Study Team.
Unit of Paediatric and Perinatal Epidemiology, Department of Child
Health, University of Bristol, UK.
BACKGROUND: Improved hygiene in Westernised regions of the world may be partly responsible for the increased prevalence of diseases of the immune system, such as asthma and atopy. There is a paucity of data on cleanliness norms in young children in the UK and there has been no attempt to identify factors that influence the adoption of particular hygiene practices in the home. AIMS: To examine levels of hygiene in a contemporary cohort of children and identify social and lifestyle factors influencing hygiene practices in the home. METHODS: The sample under study are participants in the Avon Longitudinal Study of Parents and Children (ALSPAC). Parental self completion questionnaires provided data on hygiene levels in children at 15 months of age, and a hygiene score was derived from these responses. Multivariable logistic regression models investigated associations between high hygiene scores (top quintile) and a number of perinatal, maternal, social, and environmental factors. RESULTS: Maternal smoking during pregnancy, low maternal educational achievement, and living in local authority housing were factors independently associated with high hygiene scores, as was increased use of chemical household products. High hygiene scores were inversely related to living in damp housing and attendance at day care. There were no gender or ethnic differences in hygiene score. CONCLUSION: Important data on cleanliness norms for infants have been presented. The adoption of hygiene practices is influenced to some degree by social, lifestyle, and environmental factors-with higher hygiene scores occurring in more socially disadvantaged groups. Increased use of chemical household products in the more socially disadvantaged groups within ALSPAC has emerged as an important confounder in any study of hygiene and ill health.