Presentation on technology and solutions in the WASH sector given during the Fall 2011 semester at Emory University for the class 'Water, Sanitation, and Hygiene in Developing Countries" (GH 529).
2. SOlar Water DISinfection
SODIS is a simple,
cost-effective, pointof-use method of
treating water using
UV rays from the sun
In some studies,
SODIS has reduced
diarrheal disease by
approximately 30% in
children1
Image Source: http://news.bbc.co.uk/2/hi/science/nature/4048719.stm
1. Sobsey, Mark, et. al. “Point of Use Household Drinking Water Filtration: A Practical, Effective Solution for Providing Sustained
Access to Safe Drinking Water in the Developing World“. Environmental Science & Technology. 2008, 42, 4261–4267. Web.
3. How SODIS Works: Overview
PET (polyethylene terephthalate)
bottles should be used
Bottles are usually put on a tin
roof, but can be anywhere in
the sun
6 hours is the proper duration in
direct sunlight; if sky is more than
50% clouded over, the bottles
should stay in the sun for 2 days
Source: http://www.sodis.ch/methode/anwendung/index_EN
Fill ¾ of the way, shake for 20
seconds to oxygenate the
water, finish filling the bottle
Not effective on turbid water
4. How SODIS Works: Details
Human pathogens are used to
dark environments (human GI
tract) and are highly
susceptible to UV radiation
UV radiation causes damage
to bacterial DNA resulting in
cell death
UV radiation also produces
highly reactive oxygen species
in oxygenated water
Works on bacteria (e.g., E. coli,
V. cholerae); yeasts and molds;
some viruses (e.g., rotavirus)
Image Source: http://www.northsouth.ethz.ch/news/past_events/inaugurationnorthsouthcentre/posterexhibition/Sodis.pdf
5. Or More Technically Speaking…
Image Source: http://www.elaguapotable.com/radiacion_ultravioleta.htm
6. Where SODIS can be Used
Areas that get a lot of
sunlight
Does work in cool
temperatures, but more
effective at higher temps
Areas with highest average
solar radiation: near equator
Most developing countries
lie between the latitude lines
where SODIS is most
effective
Best used on a tin roof; can
be implemented in any
village getting enough sun
World Solar Radiation
Image Source:
http://www.matthewb.id.au/media/world_insolation_map.gif
7. Current Use
An
estimated 5 million people clean their
water using the SODIS method
SODIS projects are currently in 24 countries in
Asia, Africa, and Latin America
Selection based on number of people lacking
safe drinking water
Training sessions in homes, schools, health
centers, and other institutions (depending on
structural, political, and geographic
circumstances)
Image Source: http://www.sodis.ch/projekte/index_EN
8. Examples
Peru
Kenya
SODIS
In
Foundation
has been in Peru
since 2003 working
with a local NGO
Objective to
improve living
conditions of
10,000 families in
the Ancash region
through a series of
“healthy habits”
the Kibera slum
in Nairobi, local
NGO is setting up
water kiosks to
educate others
Source: http://www.sodis.ch/news/archiv/index_EN
9. Strengths
Simple and safe
method
Acceptability by
users because of
simplicity
No cost after
obtaining plastic
bottles
Water still tastes fresh
Bottles can be left on
any surface
If unopened, bottles
can be stored
indefinitely
Weaknesses
Need pretreatment of
water with high
turbidity
Length of time
Cannot use water that
has been polluted with
chemicals
Can only use clear
bottles
Older/scratched
bottles reduce
effectiveness
Bottles create waste
Cannot treat in larger
than 3 liter bottles
10. Sustainability
Cheap and convenient
Poor compliance,
especially after cessation
of surveillance/education
(as low as 9%)
May not perceive benefits
because even when they
drink SODIS-treated water
they tend to supplement
this with non-SODIS-treated
water
Discarded water bottles
can be problematic
Water bottles that are
scratched or damaged do
not work as well
Image Source:
http://blog.crisisaid.org/journal/2009/7/18/waterscarcity-an-issue-of-poverty.html
11. Scaling Up
Primary challenge: educating to increase
compliance
Simple water treatment makes scaling up very
achievable, if knowledge is disseminated
Does not require commercial supply chain (given
used PET bottles are available)
SODIS Advocacy campaign
Informing governments, NGOs, public authorities
(teachers, nurses, etc.)
Providing expert knowledge, training material, and
practical support for the implementation of projects
Image Source: http://www.sodis.ch/news/index_EN
12. References
1. CDC. “Household Water Treatment Options in Developing
Countries: Solar Disinfection (SODIS)”. 2008. Web. 14 Oct 2011.
2. Meierhofer, R. and Wegelin, M. “Solar Water Disinfection: A
Guide for the Application of SODIS”. SANDEC Report No 06/ 02,
2002. Web.
3. Sobsey, Mark, et. al. “Point of Use Household Drinking Water
Filtration: A Practical, Effective Solution for Providing Sustained
Access to Safe Drinking Water in the Developing World“.
Environmental Science&Technology. 2008, 42, 4261–4267. Web.
4. SODIS. “SODIS Method” and “Projects”. SODIS: Safe Drinking
Water for All, 2011. Web. 14 Oct. 2011.
PET = “recyclable #1”, coke bottles, etc. so these are very common—don’t need to get bogged down by the chemical name…Test of water turbidity: if you place it on a newspaper, can you read a headline through it (from neck to bottom) filter firstCorrugated tin works well because there are synergistic effects of the UV and the raised temperature
RAINY SEASON can be a problem: *rainwater harvesting suggested*
-Selection based on number of people lacking safe drinking water-Collaboration with experiences and reliable partner organization (including: local/international NGOs, governmental development organizations, and the UN organization), who is responsible for the implementation in the field-Training in home, schools, health centers, and other institutions – selected based on the local structures, geographic circumstances, and political situation-Work several years in the project areas to achieve long-term application of SODIS-Sensitize governments for the SODIS methods in order to achieve a national dissemination-Guides and training materials (videos, flyers, posters, children’s books) in many languages
PERU EXAMPLE: healthy habits include how to treat drinking water using SODIS, as well as solar showers, improved cooking stoves (to reduce consumption of firewood and improve indoor air quality).KENYA EXAMPLE: Women groups advise their neighbors on drinking water treatment and hygiene issues and sell products for treatment and hygiene. In the slums of Nyalenda and Manyatta in West Kenya, the project focus is mainly on training in schools.http://edition.cnn.com/video/?/video/world/2009/09/01/mckenzie.sun.water.cnn - Shows the application of the SODIS method in the Kibera slum in Nairobi, Kenya.
Strengths:PET bottles have been proven safe, PVC should not be used.. Labels vary country to country. Set bottles on fire to find out, as PET burns quickly and smoke smells sweet, PVC does not burn easily, does not burn when away from flame, smoke smells bitter.SODIS method does not change the taste, the way boiling water or using chlorine does.Works quickest if bottles are on a reflective surface (like corrugated iron), but can be set on any surfaceStore in a cool, dark place. Dead bacteria cannot multiply again. The only things that may grow are algae – but that does not represent a health hazard.Weaknessesrecommend replacing old bottles and bottles that are no longer transparent after about 6 to 12 months of daily use
A UNC study1 gives SODIS a poor sustainability ranking compared to other point-of-use treatments; while it is cost-effective and easy to use, compliance is very low and the overall quality of water consumed is also low, because people tend to drink both SODIS-treated water and water that was not SODIS-treated; only 9% adopted after a few months
Very possible to scale up because of simple methods. However, need to spread the word and ensure sustainability.Make learning materials and publicity in many languages and cater to illiterate and children as well.Experiences have shown that SODIS is best promoted and disseminated by local institutions with experience in community health education. A long-term training approach and repeated contact with the community is needed to create awareness on the importance of treating drinking water and to establish corresponding changes in behavior.
Developed in the 1980’s In 1991, the Swiss Federal Institute for Environmental Science and Technology began to investigate and implement SODIS to prevent diarrhea in developing countries
