Download Safe water in the home: household water treatment and safe storage

Safe water in the home: household water
treatment and safe storage
October 2008
Globally, poor water quality poses a major threat to human health. This leaflet has
been put together to provide background information on waterborne infectious
diseases and the methods which can be used in order to treat domestic water to
make it, and keep it, safe for drinking during home storage. This briefing material has
been produced for healthcare professions, the media and others who are looking for
background understanding and/or are responsible for informing the public about
infectious diseases in the home and their prevention through good hygiene practice.
Poor water quality poses a major threat to human health. Globally diarrhoeal disease
amounts to an estimated 4.1% of the total DALY burden of disease and is
responsible for the deaths of 1.8 million people every year. The burden of disease
attributable to unsafe water is mostly concentrated on children in developing
countries. A significant amount of this disease could be prevented especially in
developing countries through better access to safe water supply.
A key argument for promoting household water treatment and safe storage in
developing countries is that it can provide safe water to under-served populations
much more quickly and affordably than it takes to design, install and deliver piped
community supplies. Promotion of “point of use” water treatment has the potential to
provide immediate benefit to at risk populations until the long-term goal of providing
community water supplies can be achieved.
Drinking water quality is a problem, not only in developing countries but also in
developed countries, most particularly Eastern European countries, but also in North
America and elsewhere. Developed countries tend to take access to safe water for
granted, but situations may arise where families either intermittently (e.g. in
emergencies during a breakdown in supply) or constantly (where families rely on
small local water systems) where the family needs to take responsibility for
purification of their water supply.
How water can make you ill
Diarrhoeal disease resulting from consumption of contaminated water is due to a
number of waterborne pathogens including:
Bacterial
Cholera (Vibrio cholera)
Typhoid (Salmonella typhii)
Viral
hepatitis A
poliovirus
Protozoa
Cryptosporidiosis
(Cryptosporidium
Helminths
Roundworms:
Guinea worm
Bacillary dysentery (Shigella spp)
Campylobacter spp
Salmonella spp.
Escherichia coli O157
norovirus
parvum)
Giardiasis
(Giardia lamblia)
Flatworms:
Contaminated water supplies have the potential to cause large and explosive
epidemics of diarrhoeal disease (e.g. cholera). The non-availability of specific
treatment for viral diseases such as hepatitis, and the increasing problem of antibiotic
resistance, which makes bacterial diseases such as typhoid and dysentery more
difficult to treat, underlines the importance of preventing water-borne disease through
effective hygiene.
What is the extent of the problem?
Universal access to safe water is seen as an essential step in reducing the burden of
infectious disease. It is estimated however, that up to 1.1 billion people still do not
have access to microbiologically safe sources of water for drinking. Even for the
remaining 5.2 billion people who have access to an “improved water source”, a
significant proportion are still drinking water which is grossly contaminated. Even in
the European region it is estimated that 120 million people do not have access to
safe drinking water.
Obtaining reliable data on the extent of diarrhoeal illness, the causative organisms,
and the extent to which this illness is water-borne is difficult. Although mortality from
diarrhoeal disease in developing countries has declined, there is little change in
morbidity rates compared with previously described incidences. It is estimated that
residents of developing nations may experience between 5 and 20 episodes of
diarrhoea per year whilst residents of developed countries experience 1 episode of
diarrhoeal illness every 2 years. In European countries and North America, there are
now fewer risks of epidemics from water contaminated with pathogens such as
cholera and typhoid or viral hepatitis, but a significant amount of disease resulting
from contaminated drinking water is still reported. Even in developed countries, as
much as 15-30% of community gastroenteritis may be attributable to municipal
drinking water, despite state-of-the-art technology for water treatment and no
conventional evidence of unacceptable microbial contamination levels.
Developing countries situation
Although water-borne diseases are of immense public health importance in
developing countries, there is relatively little systematic data available on the overall
incidence and prevalence of diarrhoeal disease in these areas, and on what
proportion of this disease is water-borne. Although significant advances have been
made in the provision of community water supplies, there is concern that the health
gains from investment in water supply are being significantly compromised by the
fact that:
 Many communities have access to water that is microbiologically safe when
collected or when it leaves a treatment plant. However, substandard water
distribution systems and intermittent water pressure often lead to the introduction
of faecal contamination resulting in microbiologically contaminated water at the
consumer's tap or collection point.
 Water can become contaminated by unsafe consumer storage and handling
practices at the household level.
Page 2/7
European situation
In 2002, WHO published a report entitled “Water and Health in Europe”. Although
water quality standards are high in most European countries, outbreaks of
waterborne disease continue to occur. For 1986–1996, data from 17 countries in the
European region indicated a total of 2,567,210 cases of infectious intestinal disease,
2% of which were linked to drinking water. These 17 countries (estimated population
220 million), on average, reported 233,383 cases of gastrointestinal disease per
year. It appears that the number of outbreaks of waterborne diseases has been
increasing in countries which have experienced recent breakdown in infrastructure,
although reliable data on drinking water quality and the incidence of disease in most
countries are lacking.
North American situation
Despite the fact that most USA citizens expect to have low cost, high quality water
available in their domestic water tap, waterborne disease outbreaks still occur. Over
the periods 1999-2000 and 2001-2002 respectively 36 outbreaks (2068 cases) and
20 (1020 cases) of waterborne infectious diseases were reported. In the USA most of
the population receive their water from community systems, but these vary
considerably in the number of people they serve. A particular problem in the USA
arises from “small water systems” (i.e. systems serving 10,000 or fewer people). The
infectious disease risk from contaminated water is considered to be greater for the
water supplies of smaller communities than the larger ones. Small communities face
the greatest difficulties in supplying water of adequate quality and quantity because
they have small customer bases and often lack the resources needed to maintain
and upgrade facilities. Small water systems are also less likely to be adequately
chlorinated and routinely monitored for contaminants. Interruptions in supply as well
as violations of drinking water standards are problems for some of these systems.
Treating water in the home to make it safe for drinking
A range of different simple, low-cost physical and chemical treatment methods have
been developed which can be used to improve household water quality. Systems
which make use of two or more treatments in combination or in succession as a
means of optimising water quality are also available.
1. Chemical disinfection
 Where chlorine or iodine tablets are available, they should be used as directed by
the manufacturer. Alternatively water should be disinfected with hypochlorite in
the form of bleaching powder or hypochlorite solution for 30 mins. The final
concentration of chlorine should be 0.5-1mgm/l available chlorine after 30 mins.
The amount of chlorine needed depends mainly on the concentration of organic
matter in the water and should ideally be determined for each situation using a
test kit. If this is not available, a slight smell of chlorine is a crude indicator.
For more details on preparing chlorine solutions consult:
http://www.who.int/household_water/resources/emergencies.pdf
Page 3/7

For disinfection with iodine a concentration of 3.7 mg/l, contact time 10 mins, is
required (6.3 mg/l if virucidal contamination is suspected).
2. Boiling
 Bringing water to a rolling boil will kill pathogens effectively except at high
altitudes. A holding period of 3-5 mins will ensure that water is safe, except in
situations where contamination with spore-forming bacteria, fungal or protozoal
cysts or hepatitis virus is suspected, in which case 10 mins is advised.
3. Filtration
 Ceramic filters with small pores, often coated with silver, have been shown to be
effective at removing microbes and other suspended solids. Filters need to be
cleaned regularly to avoid them becoming reservoirs of micro-organisms. Monthly
maintenance involves scrubbing the filter to unclog pores and washing the
receptacle tank and spigot. If properly maintained, they have a long life.
 For further information, see www.potpaz.org/ or www.purifier.com.np.
4. Solar disinfection
 Solar disinfection is an effective method, especially when no chemical
disinfectants are available. Ultra-violet rays from the sun inactivate pathogens
present in water. Water should be filled to three quarters full in clear plastic
bottles and shaken thoroughly 20 times, before being filled completely. Bottles
are then exposed to sunlight (e.g. on the roof of a house) for 6 hours (or for 2
days if the days are cloudy). The water should be consumed directly from the
bottle or transferred to a clean glass for drinking. To be effective, solar
disinfection must be applied to relatively clear water.
 For further information, see www.sodis.ch or www.who.int/water_sanitation_heal
th/dwq/wsh0207/en/.
5. UV irradiation
 UV light has received renewed interest following the realisation that
Cryptosporidium or Giardia cysts are relatively resistant to chlorination but
sensitive to quite low (<10mJ/cm2) doses of UV. Most small scale (community or
household) UV systems use low pressure Mercury lamps which provide UV at
254nm wavelength.
 UV systems may be batch or flow-though and the lamps can be suspended
above the water channel or submerged in the water flow.
6. Combined floculation/disinfection systems
 Commercially produced sachets of powder are available which act by coagulating
and flocculating sediments in water followed by a timed release of chlorine.
These typically treat 10l of water. The water is normally stirred for few minutes,
strained, and allowed to stand for a half hour.
7. Multibarrier methods
 Systems which use of two or more of the above treatment in combination or in
succession as a means of optimising water quality are now available.
Page 4/7
Pre-treatment of turbid water


If water is turbid it must be pre-treated before disinfection. Water can be treated
by a number of methods. The "best" option should be selected according to what
is most applicable to the community in question.
Turbid water can be clarified by filtration through a cotton cloth to remove any
solid materials, treated with alum and bleaching powder, stored for at least 2h
and then decanted or filtered through a clean cloth. For pre-treatment add 10g
alum and 5g lime per 100l of turbid water.
The "best" option for treatment of contaminated water should be selected according
to what is most applicable and acceptable to the community in question. The
following is an assessment of the relative characteristics of the various systems:
Treatment
Availability & Technical
practicality
difficulty
Cost
Microbial
efficacy
Boiling at 100ºC
high*
low-moderate
varies
high
chemical
treatment high(chlorine or iodine)
moderate
low-moderate
moderate
high**
solar disinfection
high***
low-moderate
low
moderate
UV lamp treatment
varies****
low-moderate
moderate
to high
high
coagulation/flocculation
/sedimentation/filtration
varies
low-moderate
varies
varies
*provided a fuel source is available; **Cryptosporidium (and to a lesser extent
Giardia) are resistant; *** requires 6h exposure time, difficult to treat large volumes;
****requires a power source
For further advice on treatment of water consult:

Emergency treatment of drinking water at point-of-use. WHO technical note for
emergencies No. 5
http://www.who.int/water_sanitation_health/hygiene/envsan/tn05/en/index.html

Household Water Treatment and Safe Storage Following Emergencies and
Disasters
http://www.who.int/household_water/resources/emergencies.pdf
Keeping water clean in the home
Even in communities where an adequate supply of microbiologically safe water is
available, this water can become contaminated by unsafe consumer storage and
handling practices at the household level:
 For those in rural and peri-urban areas, who do not have piped water in the
home, water has to be collected from the community supply and stored in jars,
buckets or other vessels in the home. Many people continue to obtain their water
on a daily or other frequent basis from any available source and either carry it or
otherwise have it delivered to the home for personal use.
 For communities where the municipal water supply is intermittent, water has to be
stored for significant periods in the home in a container or tank of sufficient size.
The municipal water distribution system, is often faecally contaminated during
non-supply hours, due to leaky pipelines and sewerage system. In such homes
Page 5/7
the water may be stored in a tank which is specifically reserved for the purpose of
water storage, or e.g. in the family bath.
Collection, storage and handling of drinking water in the home, is one of the major
risk areas in respect of domestic hygiene in most developing countries.
Water storage vessels and water handling in the home
Repeated hand contact with drinking water, during collection and storage is a major
health concern:
 Water is often taken from these containers by dipping hands into the water which
may be contaminated with faecal pathogens.
 If the container is not kept covered, the water may become contaminated from
flies, cockroaches or domestic animals.
Domestic vessels for storing drinking water:
 should be made of stainless steel/porcelain/glass/burnt clay and should be
designed with a narrow neck and provided with a tap at the bottom so that hand
contact is not required.
 should always be emptied and rinsed with clean water before refilling.
Cleaning and disinfection of drinking water storage tanks in the home
Water storage tanks in the home must be kept clean because pathogens can
sometimes become established and form a permanent reservoir. Large scale water
storage tanks must be emptied and cleaned, preferably once a month, or at least
every 2-3 months. This should be done by cleaning and descaling to remove any
biological growth from the water contact surface followed by disinfection by superchlorination. For disinfection of drinking water contact surfaces, the container should
be filled with a solution containing 20-50 mg/l available chlorine for a contact period
of 10-24 hrs.
IFH Guidelines and Training Resources on Home Hygiene
1. Guidelines for prevention of infection and cross infection the domestic
environment. International Scientific Forum on Home Hygiene. Available
from: http://www.ifhhomehygiene.org/IntegratedCRD.nsf/70f1953cec47d5458025750700035d86/92111
ae38986bfbb802574dd003fc2c1?OpenDocument
2. Recommendations for selection of suitable hygiene procedures for use in
the domestic environment. International Scientific Forum on Home Hygiene.
Available from: http://www.ifhhomehygiene.org/IntegratedCRD.nsf/70f1953cec47d5458025750700035d86/24401
f935e57e79e802574e200391c43?OpenDocument
3. Guidelines for prevention of infection and cross infection the domestic
environment: focus on issues in developing countries. International
Scientific Forum on Home Hygiene. Available from: http://www.ifhhomehygiene.org/IntegratedCRD.nsf/70f1953cec47d5458025750700035d86/24eb0
6345354d067802574e1005a075d?OpenDocument
4. Home Hygiene - prevention of infection at home: a training resource for
carers and their trainers. International Scientific Forum on Home Hygiene.
Available from: http://www.ifhPage 6/7
homehygiene.org/IntegratedCRD.nsf/571fd4bd2ff8f2118025750700031676/9aaaeb
306bb3c50c80257522004b4fdc?OpenDocument
5. Home Hygiene in Developing Countries: Prevention of Infection in the Home
and Peridomestic Setting. A training resource for teachers and community
health professionals in developing countries. International Scientific Forum on
Home Hygiene. Available from: http://www.ifhhomehygiene.org/IntegratedCRD.nsf/571fd4bd2ff8f2118025750700031676/19155a
b46073e67f8025752200546d83?OpenDocument
Further Information
1.
Combatting waterborbe disease at the household level . World health
Organisation
2007http://www.who.int/water_sanitation_health/publications/combating_diseas
epart1lowres.pdf
2. Household water storage, handling and point-of-use treatment. 2005, A review
commissioned by the International Scientific Forum on Home Hygiene. http://www.ifhhomehygiene.org/IntegratedCRD.nsf/a639aacb2d462a2180257506004d35db/aa885658ec
1f19ee8025752200559653?OpenDocument .
3. The changing hygiene climate: a review of infectious disease in the home and
community. International Scientific Forum on Home Hygiene. www.ifhhomehygiene.org/IntegratedCRD.nsf/111e68ea0824afe1802575070003f039/29858aa00
6faaa22802572970064b6e8?OpenDocument
4.
The World Health Report 2004; Geneva: World Health Organisation.
5.
Meeting the MDG Drinking Water and Sanitation Target, A Mid-Term
Assessment of Progress 2004; World Health Organisation: Geneva.
http://www.who.int/water_sanitation_health/monitoring/jmp04.pdf.
6.
Sobsey, MD. Managing water in the home: accelerated gains from improved
water supply. 2002 World Health Organization, Geneva: WHO/SDE/WSH/
02.07.
7.
Bartram J, Thyssen N, Gowers A, Pond K, Lack T, eds. Water and health in
Europe: a joint report from the European Environment Agency and the WHO
Regional Office for Europe (2002). WHO Regional Publications, European
Series No. 93.
8.
Anon 2002. Surveillance for water-borne-disease outbreaks with drinking water
– United States, 1999–2000. Morbidity and Mortality Weekly Report 2002;51:128.
9.
Anon 2004. Surveillance for water-borne-disease outbreaks associated with
drinking water – United States, 2001–2002. Morbidity and Mortality Weekly
Report 2004;53:23-45.
10. Safe Water from every tap: Improving water service to small communities.1996.
National Research Council. National Academy Press, Washington DC.
11. US Environmental Protection Agency 1997 National Public Water Systems
Annual Compliance Report and update on implementation of the 1996 Safe
Drinking Water Act amendments. August 18th 1997.
Page 7/7