It is well known that water treatment at the household level can lead to dramatic improvements in drinking water quality. But does Household Water Treatment and Safe Storage (HWTS) also have global relevance? What are the potential treatment solutions and how do they function? Is there a standard strategy for successful HWTS implementation, or can we identify key components which make programs more likely to succeed? In this course you will learn about the most important water treatment methods at household level, successful implementation strategies and about assessing the impact of HWTS. MOOC SERIES “SANITATION, WATER AND SOLID WASTE FOR DEVELOPMENT” : This course is one of four in the series “Sanitation, Water and Solid Waste for Development". FRANçAIS: Dans ce MOOC, vous allez apprendre les plus importantes méthodes de traitement de l'eau au niveau des ménages, les stratégies pour une mise en œuvre réussie et l’évaluation de l’impact du traitement et stockage sûr de l'eau à domicile. ESPAñOL: Aprende acerca de los métodos más importantes de tratamiento de agua a nivel domiciliario, de estrategias de implementación eficientes y de la evaluación del impacto del tratamiento doméstico y almacenamiento seguro del agua.
3.4 Safe storage
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Del curso dictado por École Polytechnique Fédérale de Lausanne
Introduction to Household Water Treatment and Safe Storage
188 calificaciones
École Polytechnique Fédérale de Lausanne
188 calificaciones
De la lección
HWTS treatment options
During week 2 and 3 we focus on potential treatment methods. We refer first to the standards of safe drinking water and improved drinking water. Week 3 focuses on heat, ultraviolet radiation, chemical disinfection. Specific modules are provided to cover safe storage and combined methods of water treatment.
Conoce a los instructores
Rick JohnstonDr.
Joint Monitoring Programme / WHO
Sara MarksDr.
Sanitation, Water and Solid Waste for Development / Eawag
[BLANK_AUDIO]
Recall from the first week that we discussed different ways in
which drinking water can become contaminated along a safe water chain.
Safe storage of drinking water can help
to minimize such contamination risks during collection
and transport, when the source is outside
the home as well as during household storage.
Especially when water is treated at the household level, it's very important
to store it properly so that the gains in quality are not lost.
There are a number of characteristics we would
like to see in an ideal household storage container.
Perhaps the most important one is that the container
should be covered and that there should be an
opening, which is small enough to discourage people from
putting their hands into the container during water collection,
or from using a scoop or a ladle to retrieve stored water.
The opening however, should be large enough to
allow easy filling at the point of collection.
And usually openings are between five and eight centimeters in diameter,
and ideally, they have a screw cap of some kind.
Although you don't want it to be too easy to
insert hands into the container, it is good if the
container can be cleaned periodically, and in some designs a
lid can be removed and the insides can be cleaned manually.
Where this isn't possible, users are recommended to periodically add
sand or pebbles and shake them about to clean the insides.
You can also add soap or chlorine after removing the
pebbles to wash the insides of the container.
Water can be safely retrieved by pouring.
But this requires some physical effort to lift the bucket and a risk of spilling.
So it's preferred to have a tap which can be used to withdraw water.
Taps should have a fairly large bore so that the flow rates are high.
However, taps do break or leak so they should also
be simple enough to be repaired or replaced with local hardware.
Often storage containers are also used for transporting
water from the point of collection to the
household, so the container shouldn't be too large. Even a 20 or 25 liter jerry can
is very heavy when it's full. And of
course, it should be strong and stable so it
isn't easily tipped over or broken. And it's better
to be opaque to prevent the growth of algae.
If chemical disinfection is being used, it's good to use a container
size, that corresponds to an easy chemical dose typically ten or twenty liters.
And finally, the container should be
affordable and ideally available through local markets.
Here are some examples of containers
that were designed specifically for safe storage.
This is the container developed by the U.S. Centers
for Disease Control and the Pan American Health Organization,
as part of the safe water system.
It's a modified jerry can that holds 20 liters of water and costs about $5.
The Oxfam bucket has a lid with an opening and cap
built in, and the cap is attached so you can't lose it.
You can also completely remove the lid which allows very
efficient transport since the buckets can be stacked inside each other.
These also cost around $4 or $5 and while they were designed
at Oxfam in the UK, they're now produced all around the world.
In many countries in Africa, 20 liter jerry cans are
now widely used for collecting, transporting and storing water.
They're fairly easy to carry on the head though they are
heavy and have a small opening which prevents putting hands inside.
Water is normally poured out of the opening.
They're not easy to clean, and they can be quite
dirty like this example here from the Central African Republic.
On the right, you see a modified jerry can being distributed in the Philippines after
Typhoon Haiyan by the NGO Plan International with support from DFID.
These jerry cans have a large screw top for filling that also allows cleaning.
And they come with a built-in tap, that small, red, knob at the bottom.
It's very easy to convert a standard plastic
storage bucket into a safe storage container by
drilling a hole through the plastic wall to
install a tap, like this guy is doing here.
The buckets are usually then labeled
with a sticker including instructions, especially
about using the tap to withdraw water rather than dipping into the bucket.
In Haiti, where this picture was taken, this is an easy message since the tap
is seen as a sign of higher socio-economic
status and families take pride in using it.
In many cultures people like to use clay
pots, because they cool the water due to evaporation.
In some cases water is transported in clay pots, but in most areas water
is transported in plastic containers and then
transferred to clay pots at the household.
By working with local potters it is possible to modify
clay pots to have a tap, as shown in this example.
One way to demonstrate the importance of safe water storage containers is to look
at the impact that providing a storage container alone can have on water quality.
There aren't many studies available on this topic since normally safe storage
containers are distributed, along side some
kind of treatment for example chlorine disinfection.
There are a couple of studies however, that suggest that
safe storage alone can have a significant impact on water quality.
The first is a somewhat old study, it's from 2001, made in a Malawi refugee
camp, where there were repeated outbreaks of diarrhea and cholera.
Although the microbial quality at the wells,
where people collected their drinking water was good.
The camp organizers provided randomly selected 100 households with an
improved storage container, and this is what it looked like.
And households had to exchange their
existing storage containers for the new ones.
The households, along with the households that didn't get the new containers
were monitored for four months and the researchers found that fecal coliform
levels were reduced by over 50%, by the improved storage containers, or
nearly 70% if, the geometric mean rather than the arithmetic mean is used.
The biggest impact is seen on water quality directly after collecting water
at the source, with much better water quality in the improved bucket.
The researchers also found that the hands of
people collecting water had high levels of fecal bacteria
on them, further strengthening the idea that contact
between hands and water is the cause of contamination.
In addition to finding a good reduction in water quality, there
was a 30% reduction in diarrheal disease among children under age five.
And at the end of the study, households were
offered the chance to get their old storage containers back.
But the great majority of them chose to keep
the new containers indicating that they liked them and appreciated them.
More recently, 72 villages were studied in rural Benin setting.
These villages had to have at least 40% of
the household using public pumps or standpipes, but instead
in spite of having relatively good sources of water,
household water quality was quite poor at the baseline.
In half of these 72 villages, every single
household was provided with a free improved storage container.
Either a 30 liter plastic jerry can or a 30 liter clay pot, and both of these were
fitted with taps and had stickers on them encouraging
people not to put their hand inside the container.
In all, 364 households were included in the intervention,
and a similar number were monitored in the non-intervention villages.
The evaluation found that after six
to eight months after receiving the containers,
88% were still in use and actually, it was 95% of the plastic containers,
and just under 80% of the clay pots that were still being used.
And people reported significant breakage of the clay pots
and also that they were more difficult to clean.
Stored water in the improved containers had 70%
less E. coli than in the control households.
But the researchers did not find a significant impact on diarrheal disease.
So, in summary, we've seen that safe
storage containers can be designed to minimize
recontamination and we have looked at some
of the desired characteristics of a good container.
We have seen some examples of containers that are
widely used, and also I had two examples of
intervention studies that seem to show quite a significant
impact on water quality from improved storage containers alone.
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