Sandec: Department of Water and Sanitation in Developing Countries
Sandec Training Tool 1.0 – Module 3 Household Water Treatment and Safe Storage (HWTS) Summary
Summary The supply of safe drinking water qual- requisite to render the HWTS system ef- ity and quantity is important to prevent fective. Once safe for drinking, the water water and excreta-related diseases. Cur- will have to be protected from recontam- rently, 1.1 billion people still lack access ination. Appropriate vessels and correct to an improved water supply, and far handling of the stored water will ensure more rely on unsafe drinking water con- safe storage of drinking water. taining bacteria, viruses, parasites, and Not all the water used by a household also chemical pollutants. Contamination has to be of excellent quality, merely can occur at the source, during delivery the amount used for drinking or prepar- or through inaccurate handling and stor- ing food consumed uncooked should be age at household level. treated, i.e. generally less than five litres Water treatment at its point-of-use per person and day. Ready access to wa- – the household – is a significant and ter is essential as it leads not only to an highly effective instrument in reducing increased quantity of water used for hy- the global disease burden as it lowers giene purposes and improved health but the risk of recontamination and can be also to time saving – a factor benefiting rapidly deployed by vulnerable popula- mainly women and contributing to their tions. emancipation. This module presents the most im- To increase coverage and uptake of a portant and promising household wa- HWTS approach, all stakeholders have to ter treatment and safe storage (HWTS) be involved in a collaborative effort. Initi- technologies, including physical, chemi- atives must include community participa- cal and biological treatment processes: tion, education and behavioural change. • SODIS is an effective method mak- To achieve a sustainable application of ing use of solar radiation to disinfect a new HWTS system, a feasibility study small quantities of drinking water in should be conducted before starting the plastic bottles. project. • Different filtration systems, such as Though chlorination and SODIS slow sand, ceramic or defluoridation were found to be the most cost-effec- filters are used for water treatment. tive HWTS technologies, other systems Their removal efficiencies of different should not be neglected in the context of chemical or microbial contaminations further criteria. depend on the filter material. Publishing details • Boiling or pasteurisation of water is a Publisher: Eawag/Sandec (Department of Water and Sanitation in Developing simple – but expensive – method to Countries), P.O. 611, 8600 Dübendorf, reduce pathogen concentrations. Switzerland, Phone +41 (0)44 823 52 86, • Chemical disinfection with chlorine Fax +41 (0)44 823 53 99 leads to destruction and inactivation Editors: Regula Meierhofer and of pathogens, especially bacteria and Sylvie Peter viruses. Concept and Content: Melanie Savi and Karin Güdel Use of the most appropriate technolo- Layout: Melanie Savi gies is dependent on local criteria, such Copyright: Eawag/Sandec 2008 as water quality at the source or cultural Figure 1: Household water treatment and safe Eawag/Sandec compiled this material, preferences. A combination of the differ- storage (HWTS) in the context of water and however much of the text and figures are sanitation. ent systems may be necessary to entire- not Eawag/Sandec property and can be ob- tained from the internet. The modules of ly remove microbial and chemical con- the Sandec Training Tool are not commer- tamination. If the water is highly turbid, Not included in Module 3 cial products and may only be reproduced pretreatment, such as sedimentation, Ñ Water resource management freely for non-commercial purposes. The coagulation or filtration, is often a pre- Ñ Water sources, lifting and distribution user must always give credit in citations to the original author, source and copyright holder. These lecture notes and matching PowerPoint presentations are available on the CD of Sandec’s Training Tool. They can be ordered from: [email protected] Cover photo: Boy proudly presenting SODIS bottles in Vietnam. (Source: Eawag/ Sandec)
Sandec Training Tool: Module 3 Content
Content 1 – Definitions & Objectives 4 1.1 What is safe drinking water? 4 1.2 What is our focus? 5 1.3 What are the objectives of household water treatment and safe storage? 6
2 – Introduction 7 2.1 What is the global situation? 7 2.2 What are the disease-causing pathogens and how are they transmitted? 9 2.3 What are the contamination risks for drinking water? 10 Ñ Contamination at the source 10 Ñ Contamination through delivery 12 Ñ Recontamination through transport from source and handling at the household level 13 2.4 Which water treatment and safe storage systems are used at household level? 14 2.5 What are the advantages of household water treatment versus centralised treatment systems 15
3 – Systems and Technologies 16 3.1 What is SODIS (Solar Water Disinfection)? 16 3.2 What are slow sand filters? 19 3.3 What is ceramic and terracotta (clay) filtration? 20 3.4 What are household defluoridation filters? 22 3.5 What is water boiling and pasteurisation? 23 3.6 What is chemical disinfection? 24 3.7 What is flocculation and sedimentation? 26 3.8 What HWTS system should be chosen? 28 3.9 What is safe storage? 29
4 – Non-technical aspects 31 4.1 What are the quantitative water aspects? 31 4.2 What are the political and institutional aspects? 32 4.3 What are the socio-cultural aspects? 33 4.4 What are the financial and economic aspects? 34
5 – References and Links 36 Ñ References 36 Ñ Weblinks 37
Sandec Training Tool: Module 3 1 – Definitions & Objectives
1.1 What is safe drinking water?
Ñ Safe drinking water includes microbial, chemical and aesthetic aspects. Ñ The supply of safe drinking water quality and quantity is important to prevent water and excreta-related diseases.
According to the drinking water quality Pathogen Infectious dose • Other naturally occurring chemicals, guidelines of the World Health Organisa- Shigella 101-2 organisms including uranium and selenium, may tion (WHO), water is essential to sustain Campylobacter jejuni 102-5 organisms also give rise to health concern when life, and a satisfactory (adequate, safe Salmonella 105 organisms they are present in excess. and accessible) supply must be availa- • The presence of nitrate and nitrite Escherichia coli 108 organisms ble to all. Access to safe drinking water in water has been associated with 8 is the key to health. Every effort should Vibrio cholerae 10 organisms methaemoglobinaemia, especially in 2-5 be undertaken to achieve a drinking wa- Giarda lamblia 10 cysts bottle-fed infants. Nitrate may arise ter quality as safe as practicable. Infants, Entamoeba histolitica 102-5 cysts from the excessive application of fer- young children, people who are debili- Table 1: Infectious dose of enteric pathogens. tilisers or from leaching of wastewa- tated or living under unsanitary condi- (Mandell et al., 1995 in Meierhofer et al., ter or other organic waste into surface 2002, p. 29) tions and the elderly are at greatest water and groundwater. risk of water-related disease. The nature • Particularly in areas with aggressive and form of drinking water standards lised egg may already cause an infection. or acidic waters, the use of lead pipes may vary among countries and regions. While water can be a significant source and fittings or solder can result in There is no single, universally applicable of infectious organisms, many of the elevated lead levels in drinking wa- approach. (WHO, 2006a, p. 1) waterborne diseases can also be trans- ter, which cause adverse neurologi- mitted by other routes, including person- cal effects. Microbial safety to-person contact, droplets, aerosols, (WHO, 2006a, p. 6) The greatest microbial risks are associ- and food intake. (WHO, 2006a, p. 3) ated with ingestion of water contaminat- Aesthetic aspects ed by human or animal faeces. Faeces Chemical safety Water should be tasteless and odour- can be a source of pathogenic bacteria, Health concerns associated with chem- less. In assessing the quality of drink- viruses, protozoa, and helminths. Fae- ical constituents of drinking water ing water, consumers rely generally on cally derived pathogens are the prin- differ from those associated with mi- their senses. Since the microbial, chemi- cipal concerns in setting health-based crobial contamination. They arise prima- cal and physical water constituents may targets for microbial safety. Microbial rily from the ability of chemical constit- affect appearance, odour or taste of the water quality often varies rapidly and over uents to cause adverse health effects water, the consumer will assess the qual- a wide range. Short-term peaks in patho- after prolonged periods of exposure. ity and acceptability of the water on the gen concentration may increase disease Few chemical constituents of water can basis of these criteria. Although these risks considerably and trigger outbreaks lead to health problems after a single ex- substances may have no direct health ef- of waterborne diseases. Furthermore, by posure, except if the drinking water sup- fects, a highly turbid and coloured water the time microbial contamination is de- ply is subjected to a massive accidental of objectionable taste or odour may be tected, many people may have already contamination. Moreover, experience re- regarded as unsafe by consumers and been exposed. Drinking water contami- veals that in many of these incidents the therefore rejected. In extreme cases, nated by waterborne diseases should be water becomes undrinkable owing to un- consumers may avoid aesthetically unac- particularly avoided as it could lead to the acceptable taste, odour and appearance. ceptable but otherwise safe drinking wa- simultaneous infection of a large number Numerous chemicals may occur in drink- ter in favour of more pleasant but poten- of persons and affect a potentially high ing water, however, only a few are of tially unsafe sources. It is therefore wise proportion of the community. immediate health concern in any given to be aware of consumer perceptions. In addition to faecally-borne patho- circumstance, such as: (WHO, 2006a, p. 7) gens, other microbial hazards (e.g. guinea • Exposure to high levels of naturally oc- worm) may be of public health concern. curring fluoride can lead to mottling of Module 2 contains details on the health The infective stages of many helminths, teeth and, in severe cases, crippling aspects of drinking water. such as parasitic roundworms and flat- skeletal fluorosis. worms, can be transmitted to humans • Similarly, excess exposure to natural- through drinking water. These patho- ly occurring arsenic in drinking water gens should be absent from drinking wa- may lead to a significant risk of cancer ter, since a single mature larva or ferti- and skin lesion.
Sandec Training Tool: Module 3 1 – Definitions & Objectives
Quantitative aspects cleaning, or personal hygiene. The quan- Further questions Individual drinking water needs vary de- tity of water is also important to prevent Ñ Can the household members them- selves control the drinking water quality? pending on climate, physical activity water-related diseases, i.e. if a mother and culture. For high water consumers, has enough water available for hygienic Ñ Are the consumers aware of the type of contamination of their drinking water? about two litres per day are required for a purposes, like washing hands, she also (e.g. excess fluoride, helminth eggs or 60-kg person and one litre per day for a reduces the risk of diseases for herself other sources?) 10-kg child.
E. coli, Faecal coliforms 0 CFU / 100ml (CFU: Colony forming units) Additional info Turbidity 0.1 - 5 NTU (NTU: Nephelometric turbidity units) Ñ WHO (2006): Guidelines for drinking wa- ter quality [electronic resource]: incorpo- Colour 15 TCU (TCU: True colour units) rating first addendum. Vol. 1, Recommen- Iron Not of health concern at concentrations normally observed in dations. – 3rd ed. WHO, Geneva. www. drinking water who.int/water_sanitation_health/dwq/gd- Manganese 0.4 mg/litre wq0506begin.pdf (last accessed 30.07.08) Arsenic 0.01 mg/litre Download available on the CD of Sandec’s Training Tool and from the Internet. Fluoride 1.5 mg/litre (Volume of water consumed and intake from other sources should be considered) Nitrate 50 mg/litre (short-term exposure) 0.2 mg/litre (long-term exposure)
Table 2: Guideline values for different contaminants. (Compiled from WHO, 2006a)
1.2 What is our focus?
Ñ This module addresses the treatment of water at household level: potential systems and technologies, their operation as well as their advantages and limitations, including the safe storage of drinking water.
Health can be compromised when harm- er than it will take to design, install and ful bacteria, viruses or parasites contami- deliver piped community water supplies. nate drinking water either at the source, (Sobsey, 2002, p. iii) Terminology through seepage of contaminated run- While toxic chemicals in drinking wa- Household-level approaches to drinking water treatment and safe storage are also off water or within the piped distribution ter are an important public health con- commonly referred to as managing the wa- system. Moreover, unhygienic handling cern, it has been repeatedly demonstrat- ter at “point-of-use”. This term or its ab- of water during transport or within the ed and generally accepted that the most breviation “POU” typically describes the home can contaminate previously safe important and immediate risks to human same procedures as other abbreviations water. For these reasons, many with health of using contaminated drinking derived from household water treatment, like “HHWT” or “HWT” or “HWTS”. (The access to improved water supplies water are those from enteric microbes “S” in “HWTS” refers to safe storage.) through piped connections, protected of faecal origin or other sources. Hence, “Household water management” is also wells or other improved sources are, in this training tool module centres on sys- commonly used and can encompass both fact, exposed to contaminated water. tems and technologies for the protection treatment and storage. All these terms can Therefore, potentially billions of people and improvement of the microbiological refer to a variety of treatment procedures, for example, with chlorine or other chemi- can benefit from effective household wa- quality of household water as well as for cal disinfectants, sunlight or UV lamps, var- ter treatment and safe storage. (WHO, prevention and control of water-related ious filters or flocculation-disinfection 2007, p. 10) microbial diseases. However, some tech- formulations. (WHO, 2007, p. 10) Household treatment can often pro- nologies reduce both waterborne mi- vide the health benefits of safe water crobes and also certain toxic chemicals. to underserved populations much fast- (Sobsey, 2002, p. 1)
Sandec Training Tool: Module 3 1 – Definitions & Objectives
Focus of this module is on the treat- Further questions ment of water at household level. It Ñ How can the safety of a seemingly improved water source be determined? addresses the systems and technolo- Ñ Could water resource management and water supply influence the application of HWTS gies used to improve the microbiologi- systems? cal water quality, their operation, as well as their advantages and limitations. The Additional info Ñ WHO (2007): Combating waterborne disease at the household level. WHO/The Internation- question of safe storage of drinking wa- al Network to Promote Household Water Treatment and Safe Storage, Geneva. www.who.int/ ter is also discussed. Once the water is household_water/advocacy/combating_disease/en/index.html (last accessed 30.07.08) treated, how can it be protected from re- Download available on the CD of Sandec’s Training Tool and from the Internet. contamination? The aspects of water resource man- agement and water supply are not dis- cussed in detail in this Module.
1.3 What are the objectives of household water treatment and safe storage?
Ñ The objective of HWTS is not to replace the installation of water supply infrastructure but to complement the effort of providing safe drinking water to the consumers and, therewith, contribute to reducing water-related diseases.
Currently, 1.1 billion people lack access safety component of this target and Further questions to improved water sources (e.g. a house- would significantly contribute to meet- Ñ If investments and efforts are put into HWTS, can treatment at community level hold connection or a public standpipe, cf. ing the MDGs in situations where access be neglected? Or would it be safer to treat Chapter 2.3). However, many more are to water supplies is secure but house- the water twice as an additional supplied with water unsafe for consump- hold water quality is not ensured. (WHO, precautionary measure? tion. (WHO/UNICEF, 2000, p. 7) 2007, p. 13) Ñ Is HWTS a permanent solution or only The Millennium Development Goal 7, The availability of sufficient water is regarded as a temporary measure until an Target 10, calls for reducing by half the key to a consistent practice of hygiene improved water supply with safe water is proportion of people without sustain- behaviour. Therefore, the objective of installed? able access to safe drinking water by HWTS is not to replace the installa- 2015. Reaching this target implies tack- tion of water supply infrastructure but to Additional info ling both the quantity and quality dimen- complement the effort in providing safe Ñ WHO (2007): Combating waterborne disease at the household level. WHO / The sions to drinking water provision. How- drinking water to the consumers and, International Network to Promote House- ever, studies suggest that depending on therewith, contribute to reducing global hold Water Treatment and Safe Storage, local conditions, a significant proportion diarrhoea. Geneva. www.who.int/household_water/ of water from these sources may be con- advocacy/combating_disease/en/index. taminated. In the light of these findings, A HWTS must: html (last accessed 30.07.08) great efforts are required not only to ex- • Reduce the risk of disease transmis- Ñ WHO/UNICEF (2005): Water for Life - tend services to the unserved but also to sion through drinking water by supply- Making it happen. WHO/UNICEF, Gene- va. www.who.int/water_sanitation_health/ ensure these services are indeed supply- ing safe water achieved through: monitoring/jmp2005/en/index.html (last ac- ing safe water. (WHO, 2007, p. 13) – protection of the source cessed 30.07.08) A recently published study estimat- – treatment at the source Download available on the CD of Sandec’s ed that improvements in drinking water – safe delivery Training Tool and from the Internet. quality through household water treat- – treatment at household level ment leads to a reduction of diarrhoea – safe storage to prevent recontami- episodes by 39 %. (Fewtrell et al., 2005 nation in WHO/UNICEF, 2005, p. 13) • Be affordable to all Household-level interventions can • Be easy to operate and maintain make an immediate contribution to the • Be culturally acceptable
Sandec Training Tool: Module 3 2 – Introduction
2.1 What is the global situation?
Ñ 1.1 billion people have no access to an improved water supply, most of them in Asia. Ñ According to a recent review, household-based interventions are about twice as effective in preventing diarrhoeal disease than improved wells, boreholes and communal standpipes. Ñ HWTS is therefore an important instrument in reducing the global diarrhoea burden.
Globally, 1.1 billion people are without access to improved water supply or near- ly one fifth of the world population. (WHO / UNICEF, 2000, p. 7) Figure 2 illus- trates the global differences in improved drinking water use. Within one region, urban coverage is mostly higher than rural coverage, with the greatest differences between urban and rural water access in Africa and Oce- ania (cf. figure 3). In 1990, 77 % of the world popula- tion used improved drinking water sourc- es. Considerable progress was made Figure 2: Percentage of population using improved drinking water sources in 2004. (WHO/ between 1990 and 2002, with about UNICEF, 2006, p. 8) 1.1 billion people gaining access to im- proved water sources. Global coverage Rural Urban in 2002 reached 83 %, putting the world on track to achieve the MDG target. The region that made the greatest progress was South Asia, which increased cover- age from 71 – 84 % between 1990 and 2002. This jump was fuelled primarily by increased use of improved water sourc- Figure 3: Rural and urban water supply coverage by region. (WHO/UNICEF, 2000, p. 10) es in India, with a population of over 1 billion people. Progress in sub-Saha- ran Africa was also impressive: coverage increased from 49 – 58 % between 1990 and 2002. But this falls far short of the progress needed to achieve the MDG target to re- duce by half the proportion of people without sustainable access to safe drink- ing water by 2015. Obstacles to acceler- ating the rate of progress in sub-Saharan Africa include conflict and political insta- bility, high rates of population growth and low priority given to water and san- itation. What’s more, breakdown rates of water supply systems in rural Africa can be very high. Despite these obsta- cles, decentralising responsibility, own- ership and providing a choice of service levels to communities, based on their ability and willingness to pay, are among the approaches shown to be effective in speeding up progress. (WHO / UNICEF, Figure 4: Some regions are off track in reaching the Millen- 2004, p. 10) nium Development Goal of the water and sanitation target. A key target of MDG 7 is to reduce by half the number of people without sustainable access to safe drinking water by 2015. (UNDP, 2006, p. 57)
Sandec Training Tool: Module 3 2 – Introduction
infected water source is available, it is Further questions quite likely that the water is still contam- Ñ Why are Arab States and sub-Sahara Africa off track in reaching the goal of inated and needs further treatment at reducing by half the number of people household level. without sustainable access to safe drinking water by 2015 (MDG-7, cf. Fig. 4)? Health impact of household-based Ñ The urban water supply coverage is interventions comparatively higher than the rural. How- According to a systematic review of 15 ever, considering the high density of the intervention studies by the World Bank, population in urban areas, is this water unsafer for consumption? Figure 5: Percentage of water supply household-based water treatment and effectively disinfected (free residual chlorine safe storage was associated with a 39 % > 0.1mg/l), and percentage of drinking water quality test results violating national stand- reduction in diarrhoeal disease morbid- Additional info ards. (Source: WHO/UNICEF, 2000, p. 26) ity compared to a 25 % reduction by im- Ñ UNDP (2006): Human Development Re- port 2006. Beyond scarcity: Power, pover- proved water supply. (Fewtrell et al., ty and the global water crisis, New York. Drinking water quality 2005 in WHO/UNICEF, 2005, p. 13) http://hdr.undp.org/en/reports/global/ Not all assumingly safe water is actually A more recent and comprehensive hdr2006/ (last accessed 08.08.08) of good microbiological quality. Figure 5 Cochrane review covering more than Ñ WHO/UNICEF (2000): Global Water reveals the proportion of drinking water 38 randomized, controlled trials and Supply and Sanitation Assessment 2000 samples violating national standards as 53 000 people in 19 countries revealed Report. WHO/UNICEF. www.who.int/ regards microbiological, chemical, phys- that household-based interventions were water_sanitation_health/monitoring/glo- balassess/en/ (last accessed 30.07.08) ical or aesthetic characteristics. (WHO/ about twice as effective in preventing di- Download available on the CD of Sandec’s UNICEF, 2000, p. 26) arrhoeal disease (47 %) than improved Training Tool and from the Internet. These test results imply that although wells, boreholes and communal stand- access to an assumingly safe and dis- pipes (27 %). (UNICEF, 2008, p. 2)
Sandec Training Tool: Module 3 2 – Introduction
2.2 What are the disease-causing pathogens and how are they transmitted?
Ñ Water and excreta-related pathogens belong to the bacteria, virus and parasite groups (protozoa and helminths). Ñ Many of these pathogens have multiple transmission routes, such as through food, water, person-to-person contact, flies or via inadequate hygiene behaviour (e.g. not washing the hands). Application of HWTS systems reduces the risk of transmission through drinking water but not of the other transmission routes.
Waterborne pathogens belong to the frequently observed in developing coun- bacteria, virus and parasite groups. Al- tries. The main factors influencing the though viruses are often not detected in health-related relevance of pathogens the water or host, they may account for transmitted through water are the path- the largest group of causative agents, ogens’ ability to survive in the envi- followed by parasites and bacteria. ronment and the number of pathogens Many common pathogens are not necessary to infect a (human) host. Well- only transmitted through water but also known and widely distributed pathogens follow other infectious pathways. Poor and their characteristics are listed in Ta- general hygiene practices are often a sig- ble 3. (Meierhofer et al., 2002, p. 3) nificant source of infection. Furthermore, The application of household water secondary contamination of drinking treatment systems, such as SODIS or water due to incorrect water handling is ceramic filters, improves the quality of Figure 6: The F-Diagram illustrates the typical transmission routes of pathogens and suggests possible interventions. (Adapted from DFID/WELL, 1998, p. 84) Health Persistence in Infective Pathogen Transmission Routes Signifcance Water Supplies Dose Bacteria drinking water and thus reduces the risk Camplobacter jejuni, C. High Moderate Moderate Coli of contracting a disease mainly trans- • Person-to-person Pathogenic E. Coli High Moderate High mitted by drinking water. Unfortunately, contact Salmonella typhii High Moderate High many of these so-called waterborne dis- • Domestic Other salmonellae High Long High eases have multiple transmission routes. contamination Shigella spp. High Short Moderate Consequently, diarrhoea-causing path- • Water Vibrio cholerae High Short High ogens can be transmitted to humans condtamination Yersinia enterocolitica High Long High through food, person-to-person contact, • Crop contamination Pseudomonas ae. Moderate May multiply High (?) and flies or through inadequate hygiene Aeromonas spp. Moderate May multiply High (?) behaviour (e.g. not washing the hands). Viruses Children are particularly exposed to many Adenovirus High ? Low different ways of becoming infected, as Polio Virus High ? Low illustrated in the “F-Diagram”: via fae- • Person-to-person ces, fingers, flies/insects, food, field/en- Hepatitis A Virus High contact ? Low Hepatitis Non-A Virus High ? Low vironment, and fluids/water. (Meierhofer • Domestic Enterovirus High contamination Long Low et al., 2002, p. 3) Norwalk Virus High • Water ? Low Norwalk-Like-Viruses Moderate contamination ? Low (?) Further questions (NLV) Ñ Where in the F-Diagram can water Rotavirus High ? Moderate quantity help interrupt the transmission Protozoa routes? Entamoeba hystolitica High • Person-to-person Moderate Low Ñ What activities or sites could lead to an contact increased infection risk for humans? Giarda spp. High • Domestic Moderate Low contamination Additional info • Contamination Ñ Module 2 of Sandec’s Training Tool: Cryptosporidium spp. High Long Low through animals Environmental Health Aspects of Water and Sanitation. Table 3: Health significance and transmission routes of water and excreta-related pathogens. (WHO, 1993 and Cairncross et al., 1993 in Meierhofer et al., 2002, p. 3)
Sandec Training Tool: Module 3 2 – Introduction
2.3 What are the contamination risks for drinking water?
Ñ Firstly, water can be already contaminated at the source (groundwater in a well or spring, rainwater, surface water etc.). However, groundwater is usually of good quality if the source is well protected. Ñ Secondly, it can be contaminated during delivery. Contamination occurs for example due to substandard water distribution systems, intermittent water pressure, illegal connections to the distribution system or during transport. Ñ Thirdly, there is a risk of recontamination via inappropriate transport, handling and storage at the household level.
Contamination at the source
Improved drinking water sources are de- Improved water sources Unimproved water sources fined in terms of technology types and levels of services more likely to provide • household connections • unprotected wells safe water than unimproved technolo- • public standpipes • unprotected springs gies. • boreholes • vendor-provided water Potential risks and hazardous situa- • protected dugwells • bottled water (unless water for tions associated with various non-piped • protected springs other uses is available from an water sources: • rainwater collections improved source) • tubewell fitted with a hand pump • tanker trucks providing water – ingress of contaminated surface water directly into borehole Table 4: Improved and unimproved sources of drinking water.
Some of the common drinking water Figure 7: Sanitary survey assessment. (Lloyd et al., 1991) sources are described hereafter. Number of Risk positive answers assessment
> 9 Very high
6, 7, 8 High
3, 4, 5 Moderate
0, 1, 2 Low Figure 8: Sanitary survey inspections points. Table 5: Evaluation of the survey. (Lloyd et al., 1991)
Sandec Training Tool: Module 3 10 2 – Introduction
Rooftop rainwater harvesting Three main components are neces- sary to collect rainwater for drinking purposes: • catchment surface • delivery system to transport the water from the roof to the storage reservoir (gutters and drainpipe) • reservoir to store the rainwater until it is used. The storage tank is fitted with an extraction device, such as a tap, rope, bucket or pump, depending on the location of the tank.
Groundwater catchment Groundwater is the water contained in subsurface rocks and soil, as well as the water accumulating in underground aquifers. Groundwater constitutes 97 % Photo 1: Rainwater harvesting. (Source: WEDC © Brian Skinner) of global freshwater and is an impor- tant source of drinking water in many re- gions of the world. It often requires little or no treatment to be suitable for drink- ing compared to surface water, which generally needs to be treated, often ex- tensively. (WHO, 2006b, p. 4)
Comparing the sources The best option is the use of high qual- ity source water. A change in source or use of a treatment process may alter the water taste, which will possibly be re- jected by the community. The risk of sur- face water contamination is very high. Groundwater is usually much purer than surface water but may be contaminated by natural chemicals or by anthropogen- ic activities (including the unhygienic use of a bucket and rope in a well). Rainwater harvested from roofs made of sheets or tiles is relatively pure, particularly if the first water after a dry period is allowed to Photo 2: Construction of a dugwell for groundwater use. (Source: Eawag/Sandec) run off to waste. (Skinner et al., 1998)
Source Advantages Disadvantages
Rainwater • Good microbiological quality • Contains few minerals • Easy use • Storage necessary
Groundwater • Good microbiological quality • Contamination possible: 2 (=shallow • Usually no treatment necessary dugwell) and 3 . • Easy use 3 (=spring) to difficult use 1 (=deep well)
Surface water • Easy access • Great risk of microbiological contamina- tion • High content of solids and algae • Treatment necessary
Table 6: Comparison of three drinking water sources.
Sandec Training Tool: Module 3 11 2 – Introduction
Contamination through delivery
Protection of the distribution system is system or via illegal or unauthorised increase risks to consumers, as a con- essential to provide safe drinking water. connections; centrated “slug” of contaminated water The nature of the distribution system, • through leaching of chemicals and can be expected to flow through the sys- which may include many kilometres of heavy metals from materials such as tem. Where household storage is used pipes, storage tanks, interconnections to pipes, solders/jointing compounds, to overcome intermittent supply, local- industrial users and the potential for tam- taps, and chemicals used in cleaning ised use of disinfectants to reduce mi- pering and vandalism, give rise to micro- and disinfection of distribution sys- crobial proliferation may be warranted. bial and chemical contamination oppor- tems; Drinking water entering the distribution tunities. Contamination can occur within • when petrol or oil diffuses through system may contain free-living amoe- the distribution system: plastic pipes. bae and environmental strains of various • when contaminated water in the sub- heterotrophic bacterial and fungal spe- surface material and especially from In each case, if the contaminated water cies. Under favourable conditions, amoe- nearby sewers surrounding the distri- contains pathogens or hazardous chemi- bae and heterotrophs, including strains bution system enters because of low cals, it is likely that consumers will be ex- of Citrobacter, Enterobacter and Kleb- internal pipe pressure or through the posed to them. Even where disinfectant siella may colonise distribution systems effect of a “pressure wave” within residuals are employed to limit microbi- and form biofilms. There is no evidence the system (infiltration/ingress); al occurrence, they may be inadequate of occurrence of most microorganisms • when contaminated water is drawn to overcome the contamination or may from biofilms (except, for example, into the distribution system or stor- be ineffective against some or all of the Legionella, which can colonise water age reservoir through backflow result- pathogen types introduced. As a result, systems in buildings) with adverse health ing from a reduction in line pressure pathogens may occur in concentrations effects to the general population through and a physical link between contami- that could lead to infection and illness. drinking water, with the possible excep- nated water and the storage or distri- Where water is supplied intermittently, tion of severely immuno-compromised bution system; the resulting low water pressure will al- people. Water temperatures and nutrient • through open or insecure water low the ingress of contaminated water concentrations are not generally elevat- storage reservoirs and aqueducts, into the system through breaks, cracks, ed enough within the distribution system which are potentially prone to surface joints, and pinholes. Intermittent sup- to support the growth of E. coli (or enter- runoff from the land and to faecal con- plies are not desirable but very common ic pathogenic bacteria) in biofilms. Thus, tamination from animals and water- in many countries and frequently asso- the presence of E. coli should be consid- fowl as well as to acts of vandalism ciated with contamination. The control ered as evidence of recent faecal con- and tampering; of water quality in intermittent supplies tamination. Natural disasters, including • through pipe bursts when existing presents a significant challenge as the flood, drought and earth tremors, may mains are repaired or replaced or risk of infiltration and backflow increases significantly affect piped water distribu- when new water mains are installed, significantly. The risks may be elevated tion systems. (WHO, 2006a, p. 62) potentially leading to the introduction seasonally as soil moisture conditions in- of contaminated soil or debris in the crease the likelihood of a pressure gradi- system; ent developing from the soil to the pipe. • through human error from unintention- Where contaminants enter the pipes in al cross-connection of wastewater or an intermittent supply, the charging of stormwater pipes to the distribution the system when supply is restored may
Sandec Training Tool: Module 3 12 2 – Introduction
Recontamination through transport from source and handling at the household level
Once the water has been treated and is Traditional Egyptian zir Plastic container used to sell vegetable oil in safe for drinking, the risk of recontami- Zambia nation through transport and handling at household level should be minimised, for example, by using containers with nar- row openings and dispensing devices, such as taps or spigots. Safe storage is a critical component of household water interventions. Re- gardless of whether or not collected household water is initially of acceptable microbiological quality, it often becomes contaminated with pathogens of faecal origin during transport and storage. Stud- ies show that use of containers with nar- Traditional cantero from El Salvador Sorai used in an intervention trial in India row openings for filling and dispensing devices, such as spouts or taps/spigots, protect the collected water during stor- age and household use. Improved con- tainers protect stored household water from the introduction of microbial con- taminants via contact with hands, dip- pers, other faecally contaminated vehi- cles or the intrusion of vectors.
Further questions Ñ What are the contamination risks of Tin bucket used in an intervention trial in Plastic container meeting the design criteria delivery systems other than piped water Malawi of the Centres for Disease Control and Pre- (e.g. transport by water vendors)? vention/Pan American Health Organisation and Ñ Why do people sometimes resort to the used in an intervention trial in Bolivia. use of surface water despite the qualita- tively better groundwater and rainwater?
Additional info Ñ WHO (2006): Guidelines for drinking wa- ter quality [electronic resource]: incorpo- rating first addendum. Vol. 1, Recommen- dations. – 3rd ed. WHO, Geneva. www. who.int/water_sanitation_health/dwq/gd- wq0506begin.pdf (last accessed 30.07.08) Download available on the CD of Sandec’s Figure 9: Some examples of traditional and modified water storage vessels to reduce Training Tool and from the Internet. contamination during storage. (Mintz et al., 1995)
Sandec Training Tool: Module 3 13 2 – Introduction
2.4 Which water treatment and safe storage systems are used at household level?
Ñ The available technologies comprise physical, chemical and biological treatment processes. Ñ For highly turbid water, pretreatment is often necessary for the technologies to function efficiently. Ñ For safe drinking water storage, both traditional and modern vessels can be used under certain conditions.
Of the 83 % of the world population us- waterborne diseases include a number Many traditional water collection and ing “improved” water sources, some of physical, chemical and biological treat- storage vessels of various materials and nonetheless drink water that has been ment processes. sizes are used today in developing coun- contaminated either at source, during tries. But also newer materials, such as transport or at home. The unserved 17 % The physical processes include: aluminium and plastic, have come into have little choice but to carry home • boiling widespread use. water from unsafe sources. Simple tech- • heating (fuel and solar) niques for treating water at home and • settling storing it in safe containers could save • filtering a large number of lives each year. Since • exposing to solar UV radiation cheap treatment techniques are availa- • disinfecting with UV lamps ble, and the impact of improving water quality can be dramatic, household water The chemical processes include: Further questions treatment and safe storage could yield • coagulation / flocculation and Ñ How do we know if a HWTS technology considerable health and economic bene- precipitation is actually producing safe water? fits. (WHO/UNICEF, 2005, p. 28) • adsorption If the water at source is highly turbid, • ion exchange Additional info pretreatment may be necessary prior to • chemical disinfection with germicidal Ñ WHO/UNICEF (2005): Water for Life - the actual treatment. agents (primarily chlorine) Making it happen. WHO/UNICEF, Gene- A variety of candidate technologies va. www.who.int/water_sanitation_health/ for treatment of household water have A biological process: monitoring/jmp2005/en/index.html (last ac- cessed 30.07.08) been described and many are widely • Biologically active layer in slow sand Download available on the CD of Sandec’s used in different parts of the world. The filters Training Tool and from the Internet. technologies to improve the microbial (Sobsey, 2002, p. v) quality of household water and reduce
Sandec Training Tool: Module 3 14 2 – Introduction
2.5 What are the advantages of household water treatment versus centralised treatment systems
Ñ High efficiency, reduced risk of recontamination and independence from centralised systems are among the most important advantages of water treatment at household level.
In the past, governments in developing countries have invested much effort in installing sophisticated water treatment plants and public water supply systems, especially in urban areas. However, the conventional water treatment plants often fail to produce water safe for con- sumption. Lack of trained operators, a reliable supply of chemicals and spare parts, as well as financial constraints of- ten hinder reliable operation and mainte- nance of the centralised systems. Water shortages frequently lead to water sup- ply interruptions, and leaky distribution systems worsen the situation. Moreover, the rapid population growth in urban are- as puts an excessive stress on the exist- Photo 3: Water treatment plant. (Source: Courtesy of WEDC, © Sam Godfrey) ing water and sanitation infrastructures and creates enormous problems in plan- ning and constructing new infrastruc- tures. Thus, the inhabitants of many ur- ban centres and the rural population in developing countries only have access to poor water quality. The individual house- hold therefore has to assume the respon- sibility for turning contaminated water into safe drinking water. (Meierhofer et al., 2002, p. 2)
HWTS has numerous advantages: • Treatment can be performed directly at the point of use – the risk of recon- tamination is reduced. • Each family is responsible for es- tablishing and maintaining its own Photo 4: Water treatment at household level in Cambodia. (Source: Eawag/Sandec) safe water, thus resulting in a better control. • A household water treatment is of- • is among the most effective water, Further questions ten far more rapidly established than sanitation and health interventions Ñ Do HWTS also have drawbacks over centralised systems? Which are the building a community-based system • is highly cost-effective drawbacks? (this can be especially important in • can be rapidly deployed and taken up “disaster-related” situations, such as by vulnerable populations Additional info after an earthquake or in a refugee (WHO, 2007, p. 10) Ñ WHO (2007): Combating waterborne dis- camp). ease at the household level. WHO/The In- Though household water treatment is an ternational Network to Promote Household A growing body of researchers also sug- effective and useful approach applicable Water Treatment and Safe Storage, Gene- gest HWTS as it: in many circumstances, questions about va. www.who.int/household_water/advoca- cy/combating_disease/en/index.html (last • dramatically improves the microbial acceptability and long-term use have yet accessed 30.07.08) water quality to be addressed. (WHO/UNICEF, 2005, Download available on the CD of Sandec’s • significantly reduces diarrhoea p. 28) Training Tool and from the Internet.
Sandec Training Tool: Module 3 15 3 – Systems and Technologies
3.1 What is SODIS (Solar Water Disinfection)?
Ñ SODIS is a method using solar radiation to disinfect small quantities of drinking water in plastic bottles. Ñ SODIS is most appropriate in areas with high solar radiation, availability of bottles, community motivation, and training of users in the correct and consistent application of SODIS.
Method Synergetic effect. SODIS uses two after a few minutes at temperatures Contaminated water is filled into trans- sunlight components for water disinfec- above 60 °C (cf. “What is water boiling parent plastic bottles, preferably PET tion, i.e. UV-A radiation with its germi- and pasteurisation?” Chapter 3.5). (Mei- bottles, and exposed to full sunlight for cidal effect and infrared radiation with its erhofer et al., 2002, p. 11) five hours. During exposure, sunlight pasteurisation effect and water tempera- destroys the pathogenic bacteria and ture increase. The combined use of both Weather and climate. Efficiency of viruses. A solar radiation intensity of at UV-A radiation and heat produces a syn- the SODIS process is dependent on the least 500 W/m2 is required for five hours ergetic effect that enhances the efficien- amount of available sunlight. Solar ra- for SODIS to be efficient. This is equiva- cy of the process (cf. Fig. 13). diation is, however, unevenly distribut- lent to five hours mid-latitude sunshine Solar radiation can be divided into ed and varies in intensity from one geo- in summer. A synergetic effect of UV-A three wavelength ranges: UV radiation, graphical location to another, depending radiation and temperature occurs if the visible light and infrared radiation. UV on latitude, season and time of day. The water temperature rises above 50 °C. radiation cannot be perceived by the most favourable regions for SODIS are The disinfection process then only re- human eye. It is a very aggressive radi- located between latitude 15 °N and 35 °N quires a third of the solar radiation inten- ation that can cause severe damage to (as well as 15 °S and 35 °S). These semi- sity. The water is safe for consumption the skin and eyes and destroy living cells. arid regions are characterised by the after one hour of solar exposure at 50 °C. Luckily, most of the UV-C and UV-B light highest amount of solar radiation. Over
by the ozone (O3) layer in the atmos- direct radiation due to the limited cloud phere, which protects the earth from ra- cover and rainfall (less than 250 mm rain diation. Only a higher fraction of UV-A and usually more than 3000 hours of radiation in the 320 – 400 nm wavelength sunshine annually). The second most fa- range, near the visible violet light, reach- vourable region lies between the equa- es the surface of the earth. UV-A light tor and latitudes 15 °N and 15 °S. Due to has a lethal effect on human pathogens high humidity and frequent cloud cover, present in water. These pathogens are the amount of scattered radiation in this not well adapted to aggressive environ- region is high (about 2500 hours of sun- mental conditions as they find their spe- shine annually). It is important to note cific living conditions in the human gas- that the majority of developing countries Figure 10: Instruction for SODIS use. trointestinal tract. Therefore, they are are located between latitudes 35 °N and more sensitive to sunlight than organ- 35 °S. They can therefore rely on solar isms commonly abundant in the envi- radiation as an energy source for solar Origin of SODIS ronment. UV-A radiation, which direct- disinfection of drinking water. (Meierhof- In 1991, Eawag (Swiss Federal Institute ly interacts with the DNA, nucleic acids er et al., 2002, p. 14) of Environmental Science and Technolo- and enzymes of the living cells, chang- Solar UV-A intensity shows both sea- gy) and Sandec (Eawag’s Department of Water and Sanitation in Developing Coun- es the molecular structure and leads to sonal and daily variations. The season- tries) conducted extensive laboratory and cell death. UV radiation also reacts with al variation depends on the latitude and field experiments to develop and test the the oxygen dissolved in water and pro- is mainly responsible for the climate Solar Water Disinfection Process (SODIS). duces highly reactive forms of oxygen in that region. Regions near the equa- Both the laboratory tests and practical ex- (oxygen free radicals and hydrogen per- tor encounter lower variance of light in- perience acquired during field application revealed that SODIS is a simple, low-cost oxides). These reactive molecules also tensity during the year than regions in technology with a great potential to im- interfere with cell structures and kill the prove the health of those still lacking pathogens. access to safe drinking water. Another aspect of sunlight is its long- Since 1995, the SODIS Reference Centre wave radiation, the so-called infrared. based at Eawag/Sandec is engaged in pro- Also this radiation cannot be seen by the viding information, technical support and human eye, but the heat produced by advice to local institutions in developing countries for worldwide promotion and dis- light of the wavelength beyond 700 nm semination of the Solar Water Disinfection can be felt. The infrared radiation ab- Process. More than two million people in sorbed by the water is responsible for about 30 countries currently use SODIS. heating it up. Microorganisms are sen-
Sandec Training Tool: Module 3 16 3 – Systems and Technologies
Recommendations and technical user information the northern or southern hemisphere. In Ñ Cloudiness. SODIS efficiency is dependent on the amount of available solar energy. Beirut for example (latitude: 33 °N), the – Expose the bottle to the sun for one day if the sky is cloudless or up to 50 % cloudy (a UV-A radiation intensity reaches a peak five-hour exposure time is technically sufficient, however, since users may not wear a watch, a one-day exposure is recommended to be on the safe side). level of 18 W/m2 in June and decreases – Expose the bottle to the sun for two consecutive days if the sky is more than 50 % to 5 W/m2 in December. The seasonal cloudy. differences of solar radiation are impor- – One hour exposure time is sufficient at a water temperature of at least 50 °C. tant factors for solar water disinfection. – During days of continuous rainfall, SODIS does not perform satisfactorily. Rainwater har- vesting or boiling is recommended during these days. Seasonal radiation intensities need to be Ñ Turbidity. SODIS requires relatively clear raw water of less than 30 NTU (= Nephelometric assessed prior to SODIS implementation Turbidity Units). in a specific area. The solar radiation in- Water turbidity test tensity is also subject to daily variations. Place the water-filled bottle upright on the Less radiation energy is available with in- SODIS logo on top of a table in the shade. creasing cloudiness. During completely Look through the bottle opening to the bot- overcast days, the UV-A radiation inten- tom of the bottle. Water turbidity is less than 30 NTU if you can read the letters of sity is reduced to one third of the intensi- the SODIS logo through the water. If you ty recorded during a cloudless day. (Mei- can still see the sunrays of the logo, turbid- erhofer et al., 2002, p. 14) ity is less than 20 NTU. Figure 12: SODIS logo and instructions for Effectiveness and health impact turbidity test. At a water temperature of 30 °C and a Ñ Oxygen. SODIS works more efficiently if water contains high levels of oxygen: sunlight fluence of 555 W*h/m2 (350 – 450 nm, a produces highly reactive forms of oxygen (oxygen free radicals and hydrogen peroxides) in the water. These molecules react with cell structures and kill the pathogens. dose of solar radiation corresponding to approximately five hours of mid-latitude, Ñ Bottle material. Various types of transparent plastic materials are good transmitters of light in the UV-A and visible range of the solar spectrum. Plastic bottles are made of either midday summer sunshine) is required PET (polyethylene terephthalate) or PVC (polyvinyl chloride). Both materials contain addi- to achieve at least a 3-log (99.9 %) re- tives like UV-stabilisers to increase their stability or to protect them and their content from duction of faecal coliforms. Under these oxidation and UV radiation. Use of bottles made of PET instead of PVC is recommended as conditions, only the effect of UV-A ra- PET contains much less additives than PVC bottles. diation is present. However, the die-off Transmission of UV radiation through glass is determined by its iron oxide content. Since ordinary window glass of 2-mm thickness transmits almost no UV-A light, it cannot be used rate of faecal coliforms exposed to sun- for SODIS. However, glass bottles can be used for SODIS. Specific glass types (Pyrex, Co- light increases significantly when two rex, Vycor, Quartz) transmit significantly more UV-light than the ordinary window glass. stress factors, UV-A radiation and in- Ñ Shape of containers. UV radiation is reduced with increasing water depth. At a creased water temperature, are present, water depth of 10 cm and moderate turbidity of 26 NTU, UV-A radiation is reduced by 50 %. thus causing the so-called synergetic Therefore, the containers used for SODIS should not exceed a water depth of 10 cm. effect (cf. Fig. 13). (Meierhofer et al., Ñ Replacement of bottles. Ageing plastic bottles leads to a reduction of UV transmittance 2002, p. 11) that can, in turn, result in a less efficient inactivation of microorganisms. Transmittance SODIS is highly effective in improv- losses may be due to mechanical scratches or photoproducts. Heavily scratched, old or blind bottles should be replaced. ing the microbiological water quality at (Meierhofer et al., 2002) household level. However, it cannot al- ways guarantee a 100 % reduction of bacteria and viruses as SODIS efficiency also depends on climatic conditions and user’s handling practice. (cf. Table 7).
Inactivation rate of faecal coliforms (log/Wh/m2)
Figure 13: Synergetic effect of heat and radiation. (Meierhofer et al., 2002, p. 12)
Table 7: Microorganisms eliminated by SODIS. (Meierhofer et al., 2002, p. 12)
Sandec Training Tool: Module 3 17 3 – Systems and Technologies
SODIS is also effective in eliminating In four randomized, controlled trials, Advantages of SODIS Giardia and Cryptosporidium, but a high- SODIS reduced diarrhoeal disease inci- • Simple application er radiation intensity is required to de- dence among users from 9 – 86 %. (Con- • Recontamination is unlikely as water is stroy cysts of cryptosporidium. Cysts of roy et al., 2001, 1999 and 1996, Rose et served directly from the small, narrow- necked and capped bottles in which it amoeba only need a water temperature al., 2006, Hobbins, 2003,
Further questions Ñ Is it possible to increase the effect of SODIS? Ñ Up to which contamination level with faecal coliforms does SODIS work? Ñ Can slightly coloured bottles be used for SODIS? Ñ How should old and damaged SODIS bottles be dealt with?
Additional info Ñ Meierhofer, R. and Wegelin, M. (2002): Solar water disinfection - a guide for the application of SODIS. Eawag/Sandec, Dübendorf. www.sodis.ch/Text2002/T- EducationMaterials.htm (last accessed 28.07.08) Download available on the CD of Sandec’s Photos 5: Two Indonesia girls using SODIS as children (left), and the same girls as teenagers Training Tool and from the Internet. (right). (Source: Eawag/Sandec)
Sandec Training Tool: Module 3 18 3 – Systems and Technologies
3.2 What are slow sand filters?
Ñ If properly constructed, operated and maintained, slow sand filters are capable of removing up to 99 % enteric pathogens. Ñ A biological layer on top of the sand, the so-called “Schmutzdecke”, eliminates bacteria and other pathogens. Ñ A minor removal of arsenic, iron or manganese through adsorption and filtration also occurs.
Filtration in general biological activity both in the biological BioSand Filter A number of processes occur during fil- layer called “Schmutzdecke” and further The BioSand Filter (BSF) is a slow sand fil- ter suited for home use. The most widely tration, including mechanical straining, down in the filter bed. Appropriate slow used version of the BSF is a concrete con- absorption of suspended matter and sand filters can produce a good drinking tainer approximately 0.9 metres tall and chemicals and, particularly in slow sand water quality. (Skinner et al., 1999) 0.3 metres square filled with sand. The wa- filters, biochemical processes. Depend- ter level is maintained at 5 – 6 centime- ing on the size, type and depth of the Four processes remove pathogens and tres above the sand layer by adjusting the height of the outlet pipe. This shallow wa- filter media as well as on the flow rate other contaminants: ter layer allows a bioactive layer to grow on and physical properties of the raw wa- 1. Mechanical trapping: Sediments, top of the sand that helps reduce disease- ter, filters can remove suspended solids, cysts and worms are removed from causing organisms. A perforated plate is pathogens, certain chemicals, tastes, the water by becoming trapped in placed on top of the sand to prevent and odours. Straining and settlement are the spaces between the sand grains. disruption of the bioactive layer when water is added to the system. To use the treatment methods, which usefully pre- The spaces become smaller over system, users simply pour water into the cede filtration to reduce the amount of time, enabling the filter to trap small- BSF and collect the filtered water from the suspended solids entering the filtration er particles sooner in the sand bed. outlet pipe in a bucket. (Lantagne et al., stage. This extends the operating period The filter can remove some inorganic 2005, p. 24). of a filter prior to cleaning. Larger patho- compounds and metals if they are at- Compared to slow sand filters, BioSand Fil- ters have an intermittent water flow and a gens (e.g. parasite worm eggs) are more tached to other materials or to each higher flow rate. readily removed by filtration than small- other. Advantages: er pathogens (e.g. viruses). (Skinner et 2. Adsorption or attachment: Viruses are • Proven removal of protozoa and al., 1999) adsorbed or become attached to the approximately 90 % bacteria sand grains. Once attached, they are • One-time installation with few Method metabolised by the cells or inactivat- maintenance requirements In slow sand filtration, the water pass- ed by antiviral chemicals produced by • Long life es slowly (flow velocity of 100 – the organisms in the filter. Certain or- • High user acceptability due to ease of 2 200 l/m /h) downwards through a bed of ganic compounds are also adsorbed use, including improved look and taste fine sand. For the filter to perform well, in the sand and thus removed from of water sudden changes in the flow rate should the water. • High flow rate – up to 36 litres per hour be avoided and the water should not 3. Predation: The microorganisms with- (0.6 L per minute) be very turbid (cloudy with suspended in the “Schmutzdecke” or biologi- • Durable and robust solids), otherwise the filter will quickly cal layer consume bacteria and other • Removes turbidity, some iron, manga- clog. The raw water should contain a fair pathogens found in the water, there- nese, and arsenic amount of oxygen to promote the useful by providing highly effective water • Water quality improves with time treatment. • Sells for US$ 10 – 30 4. Natural death: Food scarcity, less • Opportunity for local businesses than optimal temperatures and a rela- (Lantagne et al., 2005,
Sandec Training Tool: Module 3 19 3 – Systems and Technologies
the sand, the biological performance of Advantages of slow sand filters Further questions the filter will again be reduced for some • Use of locally available material for filter Ñ Considering the high reproduction rate construction of bacteria in tropical climates, is a 90% re- days. This also occurs if some substanc- • No material needed for operation moval of bacteria sufficient? Is it possible es in the raw water kill the organisms in to store the treated water or should it be • Improves physical, chemical and the biological layer. (UNICEF, 2008, p. 4) consumed directly after treatment? bacteriological parameters Ñ Considering the laborious and compli- Effectiveness and health impact cated construction and maintenance of the Slow sand filters, which remove sus- Drawbacks of slow sand filters slow sand filter, is this technology appro- pended solids and microbes by means • Maintenance is crucial for removal priate for use at household level or should efficiency and delivery rate: owners of it better be used at community level? of a slime layer (Schmutzdecke) that such filters need to be motivated to develops within the top few centime- operate the filters, to carefully and Additional info tres of sand, are capable of removing correctly clean them and to carry out the Ñ Lantagne, D., Quick, R. and Mintz, E. up to 99 % enteric pathogens if proper- time-consuming and periodic task of (2005): Household water treatment and ly constructed, operated and maintained. renewing the sand bed. (Skinner et al., safe storage options in developing coun- 1999) (UNICEF, 2008, p. 4) tries: A review of current implementation Other studies reveal the following re- • Requires raw water of low turbidity practises. www.irc.nl/page/37316 (last ac- (water of > 100 NTU will cause the cessed 15.09.08) moval efficiencies: filter to clog and thus require more Download available on the CD of Sandec’s • 83 % E. coli reduction in 83 filter sam- maintenance) Training Tool and from the Internet. ples • Reduced efficiency until build up of the Ñ CAWST. Centre for Affordable Water • 96 % faecal coliforms biological layer (biological layer takes and Sanitation Technology.
3.3 What is ceramic and terracotta (clay) filtration?
Ñ This filtration method is suitable for removal of solid particles and some pathogens (depending on pore size of the filter). Ñ Ceramic filtration is most appropriate in areas where quality ceramic filter production is available, including a distribution network for replacement of broken parts and training of users on correct filter maintenance and use.
Method ogens trapped in the pores. Some filters the water storage receptacle.
Sandec Training Tool: Module 3 20 3 – Systems and Technologies
Figure 15: Design option for candle filters. Manufactured filter units as illustrated in (a) are available but costly. If filter candles are available, they can be fitted into earthenware pots (b); an alternative arrangement to avoid watertight connections through the jars is the use of a siphon pipe (c); open porous-clay jars (d) can also be used. (Skinner et al., 1999)
Effectiveness and health impact Advantages of ceramic and The effectiveness of ceramic filters at terracotta filters • Long life if the filter remains unbroken removing bacteria, viruses and proto- zoa depends on the production quality • Proven reduction of bacteria and protozoa of the ceramic filter. Most ceramic filters • Proven reduction of diarrhoeal disease are effective at removing the majority of incidence in users the larger protozoal and bacterial organ-
Sandec Training Tool: Module 3 21 3 – Systems and Technologies
3.4 What are household defluoridation filters?
Ñ A filter consisting of bone char can be used for fluoride removal. A combined filter has been developed for additional elimination of heavy metals and microorganisms. Ñ Before purchasing a combined filter, the fluoride concentration of the raw water should be measured to assess the treatment requirements and lifespan of the filter
Method tivated carbon adsorbs chemical impuri- The aim of these filters is to decrease ties, such as dissolved organic material the fluoride concentration in water at and/or heavy metals. household level. Fluoride in groundwa- The water then flows first top-down, ter and surface water is mostly of geo- then bottom-up through a PVC pipe logical origin, and elevated concentra- filled with bone char (6 L). The treated tions can lead to health effects, such as water spills over to the 20-L water buck- dental and skeletal problems (cf. Module et, where it is stored and ready for with- 2). Defluoridation filters remove fluoride drawal. from the water. The filters are designed Before purchasing the combined filter, to supply a household (5 – 12 persons) the fluoride concentration of the raw wa- with water for drinking and cooking. Two ter is measured to determine the treat- types of defluoridation filters are used ment requirements and lifespan of the at household level: a simple defluorida- filter. After purchasing the filter, the first tion bucket which removes only fluoride few litres of treated water have to be dis- from drinking water and a combined fil- carded due to elevated turbidity and col- ter, which also eliminates heavy metals our. Thereafter, the treated water is col- and microorganisms from the water. The ourless and tasteless. The upper bucket latter is presented hereafter. is refilled with raw water. The users can The combined filter consists of two withdraw treated water at any time as filter processes within the same system. contact time in the bone char filter is Since the upper bucket for raw water regulated by the flow around the candle storage is transparent, the water level is filter. The surface of the ceramic filter visible without opening the lid. The raw needs to be washed regularly as soon as water passes through a ceramic candle the flow rate decreases. Washing should filter containing silver nitrate and activat- be carried out with clean water and a ed carbon. Two different processes lead soft cloth. If the fluoride concentration in to the removal of microorganisms: filtra- the outlet exceeds 1.5 mg/L the saturat- tion through the ceramic candle and tox- ed filter medium has to be replaced. ic silver nitrate kills the microorganisms flowing through the filter. Moreover, ac- Effectiveness and health impact Studies on fluoride removal efficiency of defluoridation filters of CDN WQ (Catho- lic Diocese of Nakuru, Water Quality sec- tion) conducted by Mavura et al. (2002) in Kenya exhibited very high F remov- al efficiencies ranging between 97.4 % and 99.8 % (in general > 99 %). Accord- ing to CDN WQ’s laboratory research, about 200 bedvolumes of water contain- ing 6 mg F/L can be treated at a flow rate of 10 bedvolumes/day before the F con- centration in the treated water exceeds the national Kenyan standard of 1.5 mg F/L. As fluoride is invisible, tasteless and odourless, regular sampling and analy- ses in the laboratory or on-site are nec- essary to ensure fluoride removal. Moni- toring studies of households carried out Photos 7: A combined defluoridation filter Figure 16: Schematic illustration of a com- in October 2006 revealed that saturated (above and middle) and the ceramic candle (below). (Source: CDN et al., 2007) bined defluoridation filter. (CDN et al., 2007) bone char is often not properly regener-
Sandec Training Tool: Module 3 22 3 – Systems and Technologies
Advantages of defluoridation filters ated either for lack of knowledge or fi- • Bone char is a suitable filter medium with a high fluoride removal efficiency. The raw nances. (CDN et al., 2007) material required is locally available and production costs are low. Due mainly to the chronic nature of • The candle filter regulates the flow through the bone char filter (users do not have to be fluorosis, studies on the health impact of concerned about the required contact time). defluoridation treatment are still lacking. • Optimal use of the adsorption capacity of the bone char due to column design. Such studies are important but challeng- • The filter medium never dries up as water flows bottom-up into the inner bucket ing, as several years are required to ob- containing bone char. tain satisfactory data. • The combined filter removes fluoride as well as microorganisms and heavy metals (no additional treatment required). Further questions (CDN et al., 2007) Ñ Is it more effective to use a combined filter or to combine two different methods Drawbacks of defluoridation filters (e.g. SODIS + simple defluoridation bucket) • Maintenance of the candle filter requires regular washing to obtain safe drinking water? • Ceramic candles may break if not handled carefully Ñ Is it realistic to expect users to regularly • Raw water with elevated turbidity cannot be treated with this filter design due to clogging control and replace their filters? of the candle filter • If treated water is not withdrawn and only raw water is added, the water may overflow Additional info from the defluoridation bucket Ñ CDN and Müller, K. (2007): CDN’s de- • The combined filter is more expensive than a simple defluoridation bucket fluoridation experiences on a household (CDN et al., 2007) scale. Catholic diocese of Nakuru, Water quality/EAWAG. www.eawag.ch/organisa- tion/abteilungen/sandec/publikationen/pub- lications_ws/downloads_ws/ws_house- hold_scale.pdf (last accessed 15.09.08) Download available on the CD of Sandec’s Training Tool and from the Internet.
3.5 What is water boiling and pasteurisation?
Ñ The boiling of water is a simple method for sterilisation of small quantities of drinking water. Even heating to pasteurisation temperatures (60 °C) for a few minutes will kill or deactivate most pathogens. Ñ The cost and time required to procure fuel, the increased risk of fire, indoor air pollution, and questions related to the environmental sustainability of boiling are all realistic drawbacks.
Methods Microbiologically contaminated water is filled in a heat-resistant vessel (cook- ing pot, steel drum) and brought to boil. At sea level, the boiling point is at 100 °C. As a rule of thumb, water should be kept boiling for one minute at sea level, and one minute boiling time added for eve- ry 1000 metres of elevation. Ideally, the water is cooled and stored in the same vessel in order to minimise the risk of re- contamination. Boiling or heat treatment of water with fuel is effective against the full range of microbial pathogens and can be employed irrespective of water turbid- ity or dissolved constituents in the wa- ter. While WHO and others recommend bringing water to a rolling boil for one Table 8: Effect of heat on selected pathogens. (Adapted from Feachem et al., 1983)
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Chulli minute, it is mainly intended as a visu- Advantages of water boiling and To pasteurise water, a simple flow-through al indication that a high temperature has pasteurisation system has been developed, which makes • Common technology been achieved; even heating to pasteur- use of waste heat generated in tradition- isation temperatures (60 ºC) for a few • Complete disinfection (if applied with al clay ovens or “chullis” in Bangladesh. A sufficient temperature and time) hollow aluminium coil is fitted into the clay minutes will kill or deactivate most path- • Can be combined with cooking and tea chulli and water is passed through the coil ogens. However, the cost and time used boiling during normal cooking events. By adjust- in procuring fuel, the potential aggrava- ing the flow rate, effluent temperature can tion of indoor air quality and associated be maintained at approximately 70 °C. Lab- Drawbacks of water boiling and oratory testing, along with over 400 field respiratory infections, the increased risk pasteurisation tests on chulli systems deployed in six pi- of fire, and questions associated with the • Boiled water has a flat taste lot villages, showed that the treatment environmental sustainability of boiling • Operation might be expensive (fuel, fire completely inactivated thermotolerant col- have led to other alternatives. (UNICEF, wood, gas etc.) iforms. The chulli system produces up to 2008, p. 4) • Method is time consuming (physical 90 litres of treated water per day at the presence needed during the heating household level without any additional time process, long cooling down time) or fuel requirement. The technology, which Effectiveness and health impact was developed to provide an alternative Table 8 lists temperatures and exposure • Chemicals are not removed source of safe drinking water in arsenic- times required to eliminate microorgan- • Water boiling is often not performed in contaminated areas, may also be widely isms. As shown, water does not have to practice because: applied wherever people consume micro- – energy is scarce and expensive be boiled in order to kill 99.9 % of the mi- biologically contaminated water. However, – electricity and kerosene are it does not remove arsenic but allows the croorganisms. Heating the water up to frequently not available use of microbiologically contaminated but 50 – 60 °C for one hour has the same ef- – firewood is generally used for arsenic-free surface water sources. fect. (Meierhofer et al., 2002, p. 11) cooking only (Fakhrul Islam et al., 2006, p. 356)
Further questions Ñ Gas stoves currently often replace traditional ovens. Could these also be used in the same way as the chullis for water pasteurisation? Ñ How could people learn about the exact time and temperature needed for pasteurisation? How can they control it to render the water treatment process as energy saving as possible?
Additional info Ñ Meierhofer, R. and Wegelin, M. (2002): Solar water disinfection - a guide for the application of SODIS. Eawag/Sandec, Dübendorf. www.sodis.ch/Text2002/T-EducationMaterials.htm (last accessed 28.07.08) Download available on the CD of Sandec’s Training Tool and from the Internet. Photo 8: Construction of a flow-through system in a traditional Bangladeshi clay oven. (Source: Richard Johnston, UNICEF in Fakhrul Islam et al., 2006)
3.6 What is chemical disinfection?
Ñ Chemical disinfection of water leads to the destruction and inactivation of pathogens, especially bacteria and viruses. The effect on parasites is limited. Ñ It is most appropriate in areas with an available and consistent supply of hypochlorite solution, with water of relatively low turbidity as well as in urban, rural and emergency situations, where educational messages promoting the correct and consistent use of the hypochlorite solution can reach users.
Method that helps to prevent recontamination. • Iodine (iodine and bromine are not rec- The disinfecting substance, such as chlo- Commonly used disinfectants are: ommended for long-term application) rine, is added to the contaminated wa- • Sodium hypochlorite (liquid bleach, • Silver in different chemical forms ter, often as sodium hypochlorite (liquid Javel water) bleach, Javel) or calcium hypochlorite • Calcium hypochlorite (chlorinated All of the above agents are commercial- (bleaching powder). The pathogens are lime, bleaching powder) ly available in different strengths. Dos- destroyed after a defined reaction time. • High test hypochlorite (HTH) ing has to be adjusted according to wa- If applied in the right amount, the sub- • Potassium permanganate ter quality and strength of a solution (or stances provide a disinfecting residual • Bromine in different chemical forms powder). In turbid water, chlorine is ab-
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sorbed by organic and inorganic matter to destroy all the pathogens but not so ing protozoa, such as cryptosporidium and no longer available for disinfection. much that taste is adversely affected. and amoeba. Numerous studies have This leads to dosing difficulties if the raw Appropriate dosage leads to a concen- shown complete removal of bacterial water source is subject to turbidity vari- tration of 0.5 mg/L free chlorine in the pathogens in hypochlorite-treated wa- ations. (Turbidity is the amount of organ- water (WHO, 2006a). In addition to so- ter in developing countries. In seven ic and inorganic substances dissolved in dium hypochlorite solution packaged in randomized control trials, the SWS re- the water). bottles, the tablets formed from dichlor- duced diarrhoeal disease incidence in Apart from boiling, chlorination is the oisocyanurate (NaDCC), a leading emer- users from 22 – 84 %. These studies, most widely practised means of treat- gency treatment of drinking water, and conducted in rural and urban areas, in- ing water at community level. Chlorine novel systems for on-site generation of clude adults, children, poor, HIV positive, must be added in sufficient quantities oxidants, such as chlorine dioxide, also and/or people using highly turbid water. play a role in household water treatment.
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3.7 What is flocculation and sedimentation?
Ñ Method used for the treatment of turbid water. Ñ Should be followed by one of the aforementioned treatment systems to eliminate microbial or chemical contamination.
Turbidity ed before being exposed. Larger parti- Moringa. Using natural materials to clar- Turbidity in drinking water is caused by cles and solids can be eliminated by stor- ify water is a long-standing technique. inadequately filtered particulate matter ing the raw water for one day, letting the Of all the materials used, seed powder present in source water or from resus- particles settle to the bottom prior to de- of the Moringa tree seems the most ef- pended sediments in the distribution canting the water. system. It may also be caused by inor- Advantages of Moringa ganic particulate matter present in some Methods • Moringa oleifera trees are hardy and groundwaters or due to sloughing of the Turbidity can be reduced by: drought-resistant, fast growing and a biofilm within the distribution system. • Coagulation / flocculation / sedimenta- source of large numbers of seeds. Water with less than 5 NTU is usually tion (e.g. using aluminium sulphate or • Moringa oleifera seeds are non-toxic and effective coagulants useful for removing acceptable to consumers; however, this crushed Moringa oleifera seeds) turbidity and bacteria from water. may vary according to the local context. • Filtration (e.g. using a sand layer or a • The cost of seed treatment is very low, (WHO, 2006a, p. 219) cloth) in most cases negligible. High turbidity is a particular challenge (Meierhofer et al., 2002, p. 15)
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PŪR fective. With a 60 % protein content, the Several systems include both a chemical coagulation step for particle removal (floccula- seed pressed cake left over from crush- tion) and a chlorination step for disinfection. This dual approach produces high-quality water. ing seeds to obtain oil can be used as A HWTS option, the so-called PŪR (Purifier of Water), was developed for sale to users and NGOs at production cost. The small sachet containing ferrous sulphate (a flocculant) and soil fertiliser, fuel for cooking and to calcium hypochlorite (a disinfectant) powder has a dual effect of particle removal and clear dirty water. The Moringa seeds are disinfectant. (Lantagne et al., 2005, p. 29) crushed and mixed with the water, as a Effectiveness and health impact natural coagulant to remove water tur- The flocculant/disinfectant powder PŪR proved its ability to remove most bacteria, viruses bidity. and protozoa, even in highly turbid waters. PŪR has also been documented to reduce diarrhoeal disease from 16 to over 90 % incidence in five randomized controlled health inter- Storage and settlement. Storing wa- vention studies. Moreover, PŪR eliminates heavy metals from water, such as arsenic, and ter for just one day can result in the die- chemical contaminants, such as pesticides. Studies on the efficiency of PŪR have been con- ducted in the laboratory, in developing countries, in rural and urban areas as well as in refugee off of more than 50 percent of most bac- camps, with poor adults and children using highly turbid water.
Photos 10: Use of PŪR: open the sachet, add the contents to an open bucket containing 10 litres of water, stir for five minutes, let the solids settle to the bottom of the bucket, strain the water through a cotton cloth into a second container, and wait 20 minutes for the hypochlorite to inactivate the microorganisms. (Lantagne et al., 2005, p. 29). (Source: UNICEF, 2008)
Further questions Additional info Ñ How can the need for water pretreat- Ñ CDC (2008): Environmental Health - Bibliography on Point-of-Use Water Disinfection 2008 ment be determined? Is there a simple CDC Fact Sheets and Other Documents on Household Water Treatment. www.ehproject.org/ turbidity test valid for all HWTS systems? ehkm/pou_bib2.html, (last accessed 21.4.2008) Ñ Is there a risk for water contamination Ñ Lantagne, D., Quick, R. and Mintz, E. (2005): Household water treatment and safe storage through turbidity treatment if, for example, options in developing countries: A review of current implementation practises. www.irc.nl/ the cloth used as filter is not clean or the page/37316 (last accessed 15.09.08) Moringa seeds contain pathogens on their Download available on the CD of Sandec’s Training Tool and from the Internet. surface? Ñ Clearinghouse Clearinghouse for low-cost household water treatment technologies.
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3.8 What HWTS system should be chosen?
Ñ There is no “best” HWTS system. The choice depends on local criteria, such as water quality at the source, cultural preferences or financial possibilities. Ñ To entirely remove microbiological and chemical contamination as well as turbidity, a combination of different systems might be necessary.
Choice of the best HWTS option in a giv- Sometimes the choice of a HWTS intervention is not systematic en area is a challenge for implementers. “We examined a BioSand Filter installation operating in a peri-urban slum with access to piped and processed municipal water – and intervention, which is not the most cost-appropri- Important criteria to consider when se- ate or effective for this setting. An investigation of source water quality prior to implementa- lecting a HWTS option include: tion would have revealed that a potentially more appropriate intervention, such as improving • Community or user specific needs and the local water supply, educating users on safe water storage to prevent recontamination or preferences. For example, if turbidi- using chlorination alone, should have been implemented.” (Lantagne et al., 2005, p. 31) ty of the source water is high, users should pretreat water by filtration or coagulation prior to disinfection and safe storage or, if users prefer a cur- rent practice, such as storing water in ceramic pots, the project should include this practice; • Mechanisms to prevent recontamina- tion of the treated water: a number of HWTS options include some form of residual protection (SWS, SODIS, PŪR). Safe storage or other mecha- nisms to prevent post-treatment con- tamination should form part of every HWTS project; and • Mechanisms (financial or other) pro- viding sustained availability: long- term access to the HWTS option re- quires not only activation of some type of supply chain but also ensur- ing that once activated, access is un- interrupted. Table 9: Different HWTS options and their performance criteria. (Adapted from Lantagne et al., (Lantagne et al., 2005) 2005, p. 19)
Combining the treatment methods Further questions Many HWTS systems require pretreat- Ñ Who decides on the appropriate combination of methods? ment as they function only with water Ñ Should a community or family concentrate on one HWTS system or should different of low turbidity. Furthermore, methods systems be available to react to possibly rapid water quality changes? used to remove chemicals do not nec- Ñ What is the health impact of routine versus sporadic use of HWTS options in the home? (Lantagne et al., 2005) essarily also remove pathogens or vice versa. Therefore, a combination of two Ñ Which HWTS system is the most appropriate for disaster situations? water treatment methods might be nec- Additional info essary to produce microbiologically and Ñ Lantagne, D., Quick, R. and Mintz, E. (2005): Household water treatment and safe storage chemically safe drinking water. options in developing countries: A review of current implementation practises. www.irc.nl/ page/37316 (last accessed 15.09.08) Download available on the CD of Sandec’s Training Tool and from the Internet.
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3.9 What is safe storage?
Ñ Safe storage of drinking water includes appropriate vessels and correct handling of the stored water. Ñ The properties of household water collection, treatment and storage vessels must be compatible with the intended uses (collection, treatment and storage), meet the daily water volume needs of the household, be practical and manageable for the users (women, men or children), and be socio-culturally acceptable.
Water from potable sources or water Since ancient times, water for house- Some of the key factors influencing turned potable by boiling, chemical treat- hold use is collected by a variety of the impact of storage vessels and condi- ment or solar disinfection remains sus- methods and stored in a variety of con- tions on household water quality are: ceptible to the introduction of contam- tainers. In developing countries, many • Handling and ease of use based on ca- inants during collection, transport and of the traditional types of water storage pacity, size, shape, weight, presence storage. The risk of diarrhoea from con- methods employing vessels of various of handles; tamination of drinking water during materials and sizes are still widely used • Durability, weight and other properties household storage, first noted in the today. These include traditional pots or related to resistance and longevity; 1960s, has since then been repeated- urns fashioned from natural materials • Presence of a coverable (preferably ly observed. Safe water storage vessels (e.g. gourds or wood) or fabricated from screw-cap) opening for filling and with tight-fitting lids and narrow mouths, clay, copper, brass, and other impervi- cleaning access but small enough to allowing users to remove water by pour- ous materials, as well as flexible bags or reduce the potential for recontamina- ing or through spigots but not by dipping, other vessels made of animal hides, oth- tion by contaminated hands, dipping have been included in both chemical and er animal parts or fabrics treated to seal utensils and other vehicles (e.g. air- solar water treatment programmes. The and prevent leakage. Today, metals, such borne dust), vectors or other sources; great challenge is to create water stor- as aluminium, steel and iron, as well as • Ability to withdraw water in a sani- age vessels that correspond to tradi- other materials, primarily plastics, have tary manner, such as via a tap, spigot, tional cultural standards and still meet come into widespread use for water col- spout or other narrow orifice; and the requirements of adequately protect- lection and storage in the form of buck- • Presence and accessibility of docu- ing treated water from recontamination. ets, jerry cans, picnic coolers, and oth- mentation on the proper use of the (Mintz et al., 2001, p. 1568) er vessel types and shapes. (Sobsey, container for water treatment and 2002, p. 8) sanitary storage. (Sobsey, 2002, p. 8)
A properly designed safe storage system should meet the following requirements: • The storage vessels must be afford- able. Locally available buckets, pots, urns, jerry cans, barrels, used bev- erage containers, flexible bags, and flagons are usually of low cost and readily available. • Beside storage, the vessel should be suitable for water collection and trans- port. • The vessel should be compatible with household water treatment meth- ods. Multiple containers are need- ed in some household water treat- ment systems. For example, one for raw, untreated water and another for treated water. The vessel materials must be compatible with the physi- cal and chemical agents used for wa- ter treatment. In case of chemical use, such as disinfectants (e.g. chlo- rine), the vessel material must not Figure 17: Some examples of good and bad storage containers.
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in chemical reactions leading to high • Fitted with a durable, protected and ter, primarily through contact with their concentrations of toxic disinfection easily closed spigot or spout for dis- hands. One fourth of the households by-products. In case of solar or heat pensing water; and were supplied with the improved water treatments, the vessel must be ca- • Provided with pictorial and/or written collection container. Analysis revealed pable of withstanding high tempera- instructions for use affixed perma- a 69 % reduction in faecal coliform lev- tures, and depending on the type of nently to the container, as well as an els in household water and 31 % less di- solar treatment, they must allow pen- affixed certificate of approval or au- arrhoeal disease among children under etration of UV radiation and/or ab- thenticity. the age of five in the group using the im- sorption of heat energy. (Sobsey, 2002, p. 9) proved bucket. (Roberts et al., 2001) (Sobsey, 2002, p. 9) Effectiveness and health impact The most appropriate water storage ves- By simply replacing unsafe with safe wa- sels for many household treatment and ter storage vessels resulted in lowering storage options are: the rates of cholera transmission in Cal- Further questions • Between 10 – 25 litres capacity, rec- cutta’s households. (Mintz et al., 2001, Ñ Which is the best storage vessel overall? tangular or cylindrical with one or p. 1567) more handles and flat bottoms for A study was conducted among a Ma- Ñ How long should water be stored? Is there a time limit for water use? Or, handling and ease of storage; lawi refugee population, which experi- regarding water quality as a function of • Made of lightweight, oxidation-resist- enced repeated outbreaks of cholera and storage time, is there a maximum water ant plastic, such as high-density poly- diarrhoea, and where water contamina- quality peak? ethylene or polypropylene for durabil- tion in the homes was found to be a sig- ity and shock resistance; nificant cause of cholera. The water in Additional info • Fitted with a 6 – 9-cm screw-cap the source wells had little or no micro- Ñ CAWST. Centre for Affordable Water opening to facilitate cleaning, but bial contamination, however, the water and Sanitation Technology.
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4.1 What are the quantitative water aspects? Ñ In developing countries, 20 litres are used on average for household purposes, compared to 150 litres in industrialised countries. Ñ Not all of this water has to be of excellent quality, merely the amount used for drinking or preparing food consumed uncooked should be treated, i.e. generally less than five litres per person and day. Ñ Ready access to water is essential as it leads both to an increased quantity of water used for hygiene purposes and improved health. (The amount of water used per person and day depends on the distance to the source). Ñ Furthermore, ready access to water results in time saving: typically half an hour to an hour per day and household. The time saved benefits mainly women and is a significant contribution to their emancipation.
The drinking water needs is estimated people with access to a house or yard at about two litres per day for a 60-kg connection or to a well inside the prop- person and one litre per day for a 10-kg erty will use larger quantities of water child.
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4.2 What are the political and institutional aspects? Ñ To increase coverage and uptake of a HWTS approach, all stakeholders have to be engaged in a collaborative effort. Ñ To design a pilot project, it is necessary to perform a feasibility study, to create awareness and change behaviour.
Scaling up HWTS expand access and coverage. Like most istries of health and water resources), Successful scaling up requires leveraging other household-based water interven- national and international NGOs, pri- existing commercial structures, donor tions, however, the provision of facilities/ vate sector, and other stakeholders to funding for campaigns (but not product products must be accompanied by an ex- organise a national stakeholders’ fo- subsidies), Ministry of Health support, tensive behavioural change programme rum/advocacy meeting on household community-based approaches, and col- to stimulate adoption and continued uti- water management to advocate for laboration by all partners. Most impor- lisation by householders. Effective and national support for HWTS. Involve all tantly, HWTS is not about products and robust implementation strategies for roll- stakeholders in a collaborative effort technologies but community mobilisa- ing out the adopted HWTS approach are to increase coverage and uptake. tion, social marketing and behavioural very important for successful scaling up. • Join and engage in the Home Water change. It is therefore important to have (UNICEF, 2008, p. 5) Treatment and Safe Storage Network a rigorous communication plan in place, The following are some suggested ac- (www.who.int/household_water). involving all partners and channels of tions to scale up HWTS in a country pro- • If applicable, carry out a pilot project communication. A recent report (Clasen, gramme: with partners identified above. 2008) identified some of the challenges • Find out about existing initiatives and • Identify and leverage existing com- of scaling up HWTS and emphasised the experience in your country or in neigh- mercial structures, donor funding for need to engage all stakeholders in a col- bouring countries. campaigns (but not product subsi- laborative effort to increase coverage and • Organise a learning and planning sem- dies). uptake. It also identified some of the op- inar on how the country office will roll • Promote partnerships with social mar- portunities for scaling up HWTS, includ- out HWTS with support from the re- keting organisations and the private ing government commitment to promote gional WASH (water, sanitation and sector, even if they are partners with awareness and generate demand; the hygiene) campaign adviser, profes- whom you have not worked before. use of schools, clinics and NGOs to en- sional institutions and/or NGOs expe- (UNICEF, 2008, p. 7) courage uptake and behavioural change; rienced in social marketing. and partnerships with social marketing • Work with the WHO office in the Design of a pilot project organisations and the private sector to country, government ministries (min- 1. Feasibility study for a sustaina- ble application. Before a sustained in- troduction and establishment of HWTS Community training in Uzbekistan methods in a household, a feasibility Since good health depends both on access to clean drinking water and on the right hygiene study should be performed in a commu- behaviour, the SODIS team in Uzbekistan provided the promoters with two complete infor- nity or a region to determine the follow- mation outlines for training sessions: one for SODIS and one for hygiene. Each team was ex- pected to adapt these outlines to the particular conditions in their village. During communi- ing points: ty meetings, the promoters introduced the SODIS method by explaining the effect of sunrays • Is water treatment needed? (Diar- and pointing out how diarrhoea is transmitted. In some cases, hygiene rules were taught rhoea incidence, quality of water at along with the SODIS method. During the agricultural peak season (cotton harvest in autumn), the source, what water treatment it was not possible to organise community meetings as the villagers were busy in the fields. methods are already practised). The community village leaders were first contacted and the promotion teams were introduced to the interested families. Through the village health posts, the promoters were informed • Are needed resources available? about families whose members had recently suffered from diarrhoea and those with small (Which methods can be practised children. These families are the ones most interested in learning and applying the with the available resources). SODIS method. The promoters were able to build a good relationship with many of the • Is the method applicable? interested households. They visited them once a week to answer their questions and find • Is the method socially acceptable? solutions to their problems. Project evaluation revealed that these people applied SODIS most consistently. • Is the method economically feasible? About 20 – 40 adults and often a substantial number of children attended the meetings. The villagers followed the meetings with interest and were even willing to participate. For exam- 2. Create awareness and achieve be- ple, after the promoters had presented the SODIS method with the help of pictures, someone havioural change. Secondly, aware- from the audience was asked to repeat the preparation of a SODIS bottle. As a reward for his ness about the importance of safe drink- participation, he was given a painted SODIS bottle. Villagers who were already applying SO- ing water for family or community health DIS shared their experiences and encouraged the audience to follow their example. The tech- should be created. Thus, promotion of nical resource persons in Uzbekistan put emphasis on participatory teaching methods, includ- ing role games. The promoters, however, rejected the latter and explained that this would systems and technologies has to be ac- make SODIS look ridiculous. Instead, the promoters decided to design their own posters with companied by education programmes hygiene rules. aiming at changing behaviour. For a suc- (Meierhofer et al., 2002, p. 42) cessful introduction of HWTS methods, choice of the right trainers is of key im-
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portance, including the relationship be- Information campaign: tween trainer and community to estab- • promotion through mass media Further questions lish behavioural change. • public exhibitions and demonstrations Ñ Who should initiate a HWTS project? (health centres) Wouldn’t it be more promising for the Training of users: • street plays, songs, puppet plays project if the initial effort originated from a • training through promoters (health • public display of posters and prompts community, an NGO or the government? workers, NGO staff, community vol- Ñ What are the most sustainable and cost- effective approaches of reaching rural and unteers) Advocacy: remote areas? (Lantagne et al., 2005, p. 33) • awareness building (participatory • involving and convincing opinion lead- methods) ers • locally adapted training materials • exchange with local authorities Additional info (posters, flyers, calendars) • involve stakeholders (NGOs, health, Ñ WHO. WHO Network for the promotion of household water treatment & safe stor- • training during group and community education and water supply sector) age.
4.3 What are the socio-cultural aspects?
Ñ Initiatives in HWTS must include community participation, education and behavioural change.
A number of studies and considerable sustainable without the inclusion of the ties within the community. Therefore, field experiences have revealed that the socio-cultural aspects of the communi- initiatives in water, hygiene and sanita- introduction of a water treatment tech- ty and without behavioural, motivation- tion must include community participa- nology is unlikely to be successful or al, educational, and participatory activi- tion, education and behavioural changes. A number of systems have been devel- oped and successfully implemented for Positive messages for hygiene education this purpose. (Sobsey, 2002, p. 50) An hour before the SODIS presentation in Viña Perdida, Doña Ricarda was already present in Some previous efforts to introduce the community room and said “I have just enough time to get water for my pigs before the presentation starts,“ “Can I accompany you?” I asked. “Of course”. Doña Ricarda brought and promote similar practices of house- a large and two smaller jerry cans as well as a cloth for carrying the load. Together we went hold water chlorination and safe stor- down to the irrigation canal running through Viña Perdida. The water was clear and cool. age in an improved vessel have possi- Downstream I saw people washing their clothes and children playing in the water. In the bly failed or achieved poor results due meantime, Doña Ricarda had filled her jerry cans with water. She gave me the large jerry can to inadequate participatory education, of 25 litres and took the two small ones. With an effort, I placed the jerry can on my back and followed Doña Ricarda who was already on her way to her house on top of the hill. I had dif- behavioural modification, motivational ficulties following her fast steps and started to work up a sweat. As we arrived, I asked Doña communication, social marketing, other Ricarda if she usually carries all this water by herself. “Of course”, she said “Every day, I car- community-based participation, and re- ry the big jerry can on my back and the two small ones in each hand. If the weather is very sponsibility. (Sobsey, 2002, p. 50) hot, I even go twice. I do not want the pigs to go to the irrigation canal and make everything dirty there. You have seen women do their laundry there and also fetch water for the kitchen from the canal”. Shortly afterwards, my local partners started introducing SODIS to the people of Viña Perdi- Further questions da now gathered in the community room. The first topic addressed were hygiene practices in Ñ Do programmes promoting HWTS the village. When answering the question on the kind of hygiene practices common in Viña systems exist that include community Perdida, only negative answers were given: “We drink dirty water from the canal, we have participation, education and behavioural no latrines, we do not wash our hands, we live together with animals, we are altogether un- change? hygienic”. The general atmosphere in the room following this discussion was not really bad Ñ What motivates users to purchase and but rather strange. This prompted me to tell the people the experience I just had with Doña use a HWTS option? (Lantagne et al., Ricarda. The steps Doña Ricarda takes to water her pigs are nothing else than hygiene prac- 2005) tice. Every day she carries about 40 litres of water uphill to prevent the pigs from messing around in the irrigation canal and dirtying the water others use further downstream for wash- ing and cooking. Doña Ricarda is making an enormous effort every day to prevent the water Additional info from being contaminated and to protect her neighbours and their children from possible diar- Ñ Wood, S., Sawyer, R. and Simpson- rhoea illnesses. “We have to be grateful to Doña Ricarda for her attitude, and I am convinced Hébert, M. (1998): PHAST step-by-step that every day all of you take many similar hygienic measures, maybe even without being guide: a participatory approach for the con- aware”. Doña Ricarda was visibly touched when I told her story to the community gathering, trol of diarrhoeal disease. WHO. www. and the atmosphere in the room changed all of a sudden. I had learned that traditional hygiene who.int/water_sanitation_health/hygiene/ is practiced everywhere. When discussing and praising these positive behaviours, people are envsan/phastep/en/index.html (last ac- far more motivated to learn and adopt new strategies. cessed 15.09.08) (Stephan Indergand-Echeverria, STI, in Meierhofer et al., 2002, p. 47) Download available from the Internet.
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4.4 What are the financial and economic aspects?
Ñ Chlorination and SODIS were found to be the most cost-effective HWTS technologies. Ñ However, other HWTS technologies should not be neglected as the context of other criteria must also be considered.
Costs / benefit effects of different 2004). However, disinfection at point-of- HWTS options use (the only HWTS option considered Cost is a critical factor in any devel- in the analysis) had the lowest cost per opment programme. Costs are highly person when compared to all non-HWTS programme-specific, they vary accord- interventions to provide improved water ing to location, implementation strategy, supply or sanitation. This initial work indi- desired endpoint, and cannot be gener- cates that HWTS options are cost-effec- alised. Programme planners must eval- tive mechanisms for providing improved uate both the costs and treatment re- water to households. (Lantagne et al., quirements of a community to determine 2005, p. 32) the most cost-effective and appropri- The point estimate for household- ate intervention. When reviewing cost based interventions in Figure 19 repre- data, it is important to compare them to sents the best available estimate of the the costs of other water and sanitation true annual cost per person covered by improvements. According to a recent the intervention, while the range reflects Figure 19: Annual cost per person and range cost-benefit evaluation, all the water and certain variations in such cost. (Clasen et of annual cost (narrow bars) for household- based interventions to improve water quality. sanitation improvements analysed were al., 2008, p. 16) (Clasen et al., 2008, p. 17) cost-beneficial in all regions of the world, Among all water quality interventions with returns of US$ 1.92 – 15.02 on each to prevent diarrhoea, chlorination is the US$ 1 invested, depending on region most cost-effective. Solar disinfection is its almost identical cost but lower over- and type of improvement (Hutton et al., only slightly less cost-effective owing to all effectiveness. Ceramic filters repre- sent an opportunity to avert higher lev- els of DALYs with additional investment. Social marketing in Zambia This represents additional costs and ben- The NGO Population Services International (PSI) is the largest social marketing NGO in the efits beyond household-based chlorina- world, with offices in more than 70 countries. PSI designs a brand name and logo for health products, sells them at low prices, distributes them through wholesale and retail commercial tion, and reflects a potential debate over networks; and generates demand for the products through behavioural change, communica- the resources that individual household- tion, such as radio and TV spots, mobile video units, point-of-sale materials, theatre perform- ers or the public sector may want to de- ances, and person-to-person communication. In October 1998, PSI launched its Zambian SWS ploy in order to achieve health returns. product, a bottle of sodium hypochlorite solution branded as “Clorin”. This programme is one Combined flocculation / disinfection was of the oldest PSI/CDC collaborations. Sales steadily increased from 732 bottles per month in October 1998 to 132,000 bottles per month in November 2003. A cholera epidemic in 1999 strongly dominated by all other interven- increased demand for Clorin; while sustained social marketing and promotion in health cen- tions, except under an assumption in tres and door-to-door visits stimulated further sales. A population-based, cross-sectional study which it can be implemented at its mini- conducted by an independent agency reported that 42 % of households said they were cur- mum cost. (Clasen et al., 2008, p. 24) rently using Clorin and 22 % reported using it in the past. However, only 13 % of households had residual chlorine in their water at the time of the unannounced visit, indicating a discrep- ancy between reported and actual use. The study did not find a lower rate of reported diar- Cost-effectiveness in the context of rhoea among users of Clorin as compared to non-users. However, using large cross-sectional other criteria studies to assess the efficacy of household water treatment options requires further refine- Cost and cost-effectiveness, though im- ment. The limitations of this study, which was the first large cross-sectional population study portant for setting health priorities, must (as opposed to a randomized study with a controlled population), impacted the results. The be considered in the context of other Clorin product is subsidised by USAID; the full cost of the 250-millilitre bottle, including pro- duction, marketing, distribution, and overhead, – amounts to US$ 0.34, and the retail price economic and non-economic criteria, es- is set at US$ 0.12. The total programme cost per person/month of protection from diarrhoea pecially if the goal is to achieve a sustain- is US$ 0.045. Increasing the price to recover full costs could have a negative impact on de- able solution by having some or all of the mand, particularly in a country like Zambia, which ranks 164th out of 177 on the Human De- cost of safe drinking water borne by the velopment Index. The programme, which needs studies on the price elasticity of demand for beneficiaries. Affordability and perceived this product, is currently implementing options to significantly lower costs. The PSI of Zam- bia project is an example of a successful social marketing intervention that creates demand value are among the other economic for a product and makes it widely available through the commercial sector. Interested NGOs criteria. A point-of-use water treatment can readily incorporate Clorin into their own programme. The two major challenges this pro- product, which may improve water qual- gramme faces are achieving financial self-sufficiency while maintaining access to the product ity at a lower cost per unit (person, and increasing demand among the highest-risk populations. With its wide Clorin use and dis- household, day, litre etc.) than some al- tribution, Zambia is an ideal location for future research on programme effectiveness in dis- ease prevention, cost-effectiveness and interventions to reduce economic and behavioural ternative product, may be important to barriers to utilisation. (Lantagne et al., 2005, p. 21) government planners, donors and policy- makers. But to consumers asked to pay
Sandec Training Tool: Module 3 34 4 – Non-technical aspects
for the product, the overriding consider- pay at that time and place. A bottle of di- position, other priorities, assessment of ation may be whether they have enough lute sodium hypochlorite for US$ 1.50, the risk to be avoided, perceived utility money on hand that day to buy it. Such which can last a family for six months, of the proposed solution etc. – all eco- “ability to pay” may depend not on the has a significantly lower unit cost than a nomic factors not strictly related to cost. cost as determined by economic analysis sachet of flocculant/disinfectant priced Non-economic factors, such as compat- but on the price the householder must at US$ 0.10 and lasting less than a week. ibility, complexity and ease of handling, Nevertheless, as companies who market also influence consumer attitudes and Cost example of ceramic filters to the poor have frequently found, con- practices with respect to adoption of an Locally manufactured ceramic PFP- sumers with limited cash may neverthe- innovative product. Cultural preferenc- design filters range in cost from US$ 7.50 less prefer the sachets because they find es also play a role. Policy-makers and – 30. Distribution, education and commu- nity motivation can add significantly to pro- them to be more affordable given their programme implementers must consid- gramme costs. Ceramic filter programmes limited cash. The minimum purchasable er these factors in addition to basic cost can achieve full cost recovery (charging the unit and minimum purchase price can and cost-effectiveness if they expect to user the full cost of product, marketing, sometimes influence the choices of poor secure some measure of cost recovery distribution, and education), partial cost re- consumers more than the unit price. Sim- in scaling up household water treatment. covery (charging the user only for the fil- ter and subsidising programme costs with ilarly, consumers’ “willingness to pay” (Clasen et al., 2008, p. 27) donor funds) or can be fully subsidised depends largely on their current cash such as in emergency situations. If a fam- ily filters 20 litres of water per day (running the filter continuously) and the filter lasts for three years, then the cost per litre wa- Further questions ter treated (including cost of filter only) is Ñ What are the current rates of purchase and use of HWTS in different demographic, socio- US$ 0.034 – 0.14. Commercially available economic and cultural groups? How do these correlate with water-related disease prevalence ceramic filter systems range in cost from rates? (Lantagne et al., 2005) tens to hundreds of US dollars, depending Ñ Combined flocculation / disinfection belongs to the less cost-effective HWTS technologies; on where they are manufactured and pur- however, it can be the most appropriate in certain situations. When could that be the case? chased and on the quality of the ceramic filters. The economics and sustainability of commercial product-based projects depend Additional info on donor funding and subsidy as well as on Ñ WHO (2007): Combating waterborne disease at the household level. WHO/The Internation- follow-up to ensure replacement parts are al Network to Promote Household Water Treatment and Safe Storage, Geneva. www.who.int/ accessible to the population using the household_water/advocacy/combating_disease/en/index.html (last accessed 30.07.08) filters.
Sandec Training Tool: Module 3 35 5 – References and Links
Fakhrul Islam, M. and Johnston, R.B. (2006): Skinner, B. and Shaw, R. (1999): Technical Bold: The key readings (additional info) Household Pasteurization of Drinking-wa- brief No. 59 - Household water treatment are available on the CD of Sandec’s ter: The Chulli Water-treatment System. J 2. Waterlines, 17(3). Training Tool. They are open source HEALTH POPUL NUTR, 24(3): 353626-. products. The user must always give Sobsey, M. (2002): Managing Water in the credit in citations to the original author, Feachem, R.G., Bradley, D.J., Garelick, H. Home: Accelerated Health Gains from Im- source and copyright holder. and Mara, D.D. (1983): Sanitation and proved Water Supply. WHO, Geneva. Disease; Health Aspects of Excreta and UNDP (2006): Human Development Report Wastewater Management (World Bank 2006. Beyond scarcity: Power, poverty and Studies in WS & S, 3). John Wiley & Sons - References the global water crisis, New York. Wiley-Interscience Publications, 501 pp. Cairncross, S. and Feachem, R.G. (1993): En- UNICEF (2008): Promotion of household wa- Fewtrell, L. et al. (2005): Water, sanitation, vironmental Health Engineering in the Trop- ter treatment and safe storage in UNICEF and hygiene interventions to reduce diar- ics: An Introductory Text. Second Edition. WASH programmes. rhoea in less developed countries: A sys- John Wiley & Sons - Wiley-Interscience tematic review and meta-analysis. Lancet Publications, 306 pp. WHO (1993): Guidelines for Drinking Water Infectious Diseases, 5(1): 42-52. Quality, 2nd ed. Vol.1 WHO, Geneva. Cairncross, S., O’Neill, D., McCoy, A. and Hobbins, M. (2003): The SODIS Health Im- Sethi, D. (2003): Health, environment and WHO (2006a): Guidelines for drinking-water pact Study. Ph.D. Thesis. Swiss Tropical In- the burden of disease; A guidance note. quality [electronic resource]: incorporating stitute Basel. DFID, London. first addendum. Vol. 1, Recommendations. – 3rd ed. WHO, Geneva. Hutton, G. and Haller, L. (2004): Evaluation of CDC (2008): Environmental Health - Bibliog- the Costs and Benefits of Water and Sani- raphy on Point-of-Use Water Disinfection WHO (2006b): Section 1: Scientific Back- tation Improvements at the Global Level. 2008 CDC Fact Sheets and Other Docu- ground. In: O. Schmoll, G. Howard, J. Chil- WHO. ments on Household Water Treatment. ton and I. Chorus (Editors), Protecting Groundwater for Health. IWA. www.ehproject.org/ehkm/pou_bib2.html, Lantagne, D., Quick, R. and Mintz, E. accessed on 21.4.2008. (2005): Household water treatment and WHO (2007): Combating waterborne disease safe storage options in developing coun- CDN and Müller, K. (2007): CDN’s defluori- at the household level. WHO/The Interna- tries: A review of current implementation dation experiences on a household scale. tional Network to Promote Household Wa- practises. Catholic diocese of Nakuru, Water qual- ter Treatment and Safe Storage, Geneva. ity/Eawag. Lloyd, B. and Helmer, R. (1991): Surveillance WHO/UNICEF (2000): Global Water Supply of drinking water quality in rural areas. Clasen, T.F. (2008): Scaling up household and Sanitation Assessment 2000 Report. Longman Scientific & Technical, New York. water treatment: looking back, seeing for- WHO/UNICEF. ward. WHO. Mandell, G.L., Bennett, J.E. and Dolin, R. WHO/UNICEF (2004): Meeting the MDG (1995): Principles and Practice of Infec- Clasen, T.F. and Boisson, S. (2006): House- drinking water and sanitation target - A tious Diseases, 1&2. Churchill Livingstone. hold-based ceramic water filters for the mid-term assessment of progress. treatment of drinking water in disaster Mavura, W.J. and Bailey, T. (2002): Fluoride WHO/UNICEF (2005): Water for Life - Mak- response: an assessment of a pilot pro- contamination in drinking water in the Rift ing it happen. WHO/UNICEF, Geneva. gramme in the Dominican Republic. Water Valley, Kenya and evaluation of locally man- Practice & Tech., 1(2). ufactured defluoridation filter. Journal of WHO/UNICEF (2006): Meeting the MDG Civil Engineering JKUAT, 8: 79-88. drinking water and sanitation target: The Clasen, T.F., Brown, J., Collin, S., Suntura, O. urban and rural challenge of the decade., and Cairncross, S. (2004): Reducing diar- Meierhofer, R. and Wegelin, M. (2002): So- Geneva. rhea through the use of household-based lar water disinfection - a guide for the ap- ceramic water filters: a randomized, con- plication of SODIS. EAWAG/SANDEC, trolled trial in rural bolivia. Am J Trop Med Dübendorf. Hyg, 70(6): 651-657. Mintz, E., Bartram, J., Lochery, P. and We- Clasen, T.F. and Haller, L. (2008): Water gelin, M. (2001): Not Just a Drop in the Quality Interventions to Prevent Diarrhoea: Bucket: Expanding Access to Point-of-Use Cost and Cost-Effectiveness. WHO. Water Treatment Systems. Am J Public Health, 91(10): 1565-1570. Conroy, R., Meegan, M., Joyce, T., Mc- Guigan, K. and Barnes, J. (1999): Solar dis- Mintz, E.D., Reiff, F.M. and Tauxe, R.V. infection of water reduces diarrhoeal dis- (1995): Safe water treatment and storage ease, an update. Archive of Diseases in in the home: A practical new strategy to Childhood, 81(4): 337-338. prevent waterborne disease. JAMA j. Am. Med. Assoc., 273(12): 948-953. Conroy, R., Meegan, M., Joyce, T., Mc- Guigan, K. and Barnes, J. (2001): Use of Roberts, L. et al. (2001): Keeping clean water solar disinfection protects children under 6 clean in a Malawi refugee camp: a random- years from cholera. Archive of Diseases in ized intervention trial. Bull World Health Or- Childhood, 85(4): 293-295. gan, 79(4): 280-7.
Conroy, R.M., Elmore-Meegan, M., Joyce, T., Rose, A. et al. (2006): Solar disinfection of McGuigan, K.G. and Barnes, J. (1996): So- water for diarrhoeal prevention in Southern lar disinfection of drinking water and diar- India. Archive of Diseases in Childhood, rhoea in Maasai children: a controlled field 91(2): 139-141. trial. The Lancet, 348(9043): 1695-1697. Skinner, B. and Shaw, R. (1998): Technical DFID/WELL (1998): Guidance manual on brief no. 58 - Household water treatment 1. water supply and sanitation programmes. Waterlines, 17(2). DFID, London.
Sandec Training Tool: Module 3 36 5 – References and Links
Weblinks
CAWST. Centre for Affordable Water and Sanitation Technology. www.cawst.org, accessed on 25.4.2008.
Clearinghouse. Clearinghouse for low-cost household water treatment technolo- gies. www.jalmandir.com, accessed on 25.4.2008.
GHEF Safe drinking water is essential. Global Health and Education Foundation. www. drinking-water.org/html/en/Overview/in- dex.html, accessed on 29.4.2008.
SODIS Solar Water Disinfection. www.sodis. ch, accessed on 22.4.2008.
WHO (2008a): WHO Network for the promo- tion of household water treatment & safe storage. www.who.int/household_water/ en/, accessed on 28.07.08.
WHO (2008b): World Health Organization - Home. www.who.int/en/, accessed on 21.4.2008.
Wood, S., Sawyer, R. and Simpson-Hébert, M. (1998): PHAST step-by-step guide: a participatory approach for the control of diarrhoeal disease. WHO. www.who. int/water_sanitation_health/hygiene/en- vsan/phastep/en/index.html, accessed on 15.09.2008.
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