Melissa Reichwage

Miranda Delahoy

SOlar Water DISinfection

SODIS is a simple, cost-effective, point-of-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.

How SODIS Works: Overview

Fill ¾ of the way, shake for 20 seconds to oxygenate the water, finish filling the bottle

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

Not effective on turbid water

Source: http://www.sodis.ch/methode/anwendung/index_EN

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

Or More Technically Speaking…

Image Source: http://www.elaguapotable.com/radiacion_ultravioleta.htm

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

Image Source:

http://www.matthewb.id.au/media/world_insolation_map.gif

World Solar Radiation

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

ExamplesPeru

SODIS 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”

Kenya

In the Kibera slum

in Nairobi, local

NGO is setting up

water kiosks to

educate others

Source: http://www.sodis.ch/news/archiv/index_EN

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

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/water-

scarcity-an-issue-of-poverty.html

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

References1. 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.

Questions?

Image Source: http://www.sodis.ch/index_EN