SODISSODISSOSOLAR LAR

DISDISINFECTIONINFECTION

Team AquafersScott Weeks, Stephen Russo, James Berg & Jamison Hill

ProcedureProcedure

© Fundacion SODIS Uniersidad Mayor de San Simon Casilla, 5783, Cochabamba, Boliviasodis@supernet.com.bo, sodisla@fcyt.umss.edu.bo

Exposure TimesExposure Times

EnvironmentEnvironment Exposure timeExposure time

< 50% cloudy< 50% cloudy 6 hr6 hr

50% - 100% cloudy50% - 100% cloudy 2 consecutive days2 consecutive days

RainyRainy SODIS not effectiveSODIS not effective

If water reaches 50If water reaches 50°C °C (122°F)(122°F)

1 hr1 hr

To be effective turbidity To be effective turbidity must be below 30 NTUmust be below 30 NTU

• Turbidity testTurbidity test

•In the shade place filled 2 Ltr bottle on SODIS logo. Look down through the top to the bottom •If you can read the letters, less then 30 NTU•If you can see the sun rays, less then 20 NTU

TurbidityTurbidity

Bottle TypeBottle Type

2 Ltr bottles usually made of PVC or PET 2 Ltr bottles usually made of PVC or PET – PET transmits UV rays more effectivelyPET transmits UV rays more effectively

PVC bottles usually have a bluish gleamPVC bottles usually have a bluish gleam If burnt PVC smoke smells pungent, PET If burnt PVC smoke smells pungent, PET

smoke smells sweetsmoke smells sweet Glass bottles can also be usedGlass bottles can also be used Should not use containers greater then Should not use containers greater then

10 cm (4 in) deep10 cm (4 in) deep

SODIS ScienceSODIS Science

Thermal (Pasteurization)Thermal (Pasteurization) UV RadiationUV Radiation

Solar energy provides two mechanisms of treatment:

Can work independently, but studies indicate synergistic effects when applied together

Thermal EffectsThermal EffectsTemperatures at which the most common Temperatures at which the most common waterborne pathogens are rapidly killed, waterborne pathogens are rapidly killed, resulting in 90 percent of the microbes resulting in 90 percent of the microbes becoming inactivated in one minute at the given becoming inactivated in one minute at the given temperature.temperature.

MicrobeMicrobe Killed Rapidly Killed Rapidly AtAt

Worms, Protozoa cysts Worms, Protozoa cysts ((Giardia,Giardia,Cryptosporidium, Cryptosporidium, EntamoebaEntamoeba))

55°C (131°F)55°C (131°F)

Bacteria (Bacteria (V. cholerae, E. coli,V. cholerae, E. coli,Shigella, Salmonella typhiShigella, Salmonella typhi), ), RotavirusRotavirus

60°C (140°F)60°C (140°F)

Hepatitis AHepatitis A virus virus 65°C (149°F) 65°C (149°F)

Source: http://solarcooking.org/newsletters/scrnov02.htm#water

UV RadiationUV Radiation

Damages living cells Damages living cells (i.e. sunburns)(i.e. sunburns)

Causes fundamental Causes fundamental changes in nucleic changes in nucleic acids/DNA acids/DNA (by producing thymine-(by producing thymine-dimers)dimers)

Excessive radiation Excessive radiation can also change can also change enzymes and other enzymes and other fundamental structuresfundamental structures

Types of UV RadiationTypes of UV Radiation

The inactivation rate of micro-organisms increases The inactivation rate of micro-organisms increases with decreasing wavelength: with decreasing wavelength:

Visible light -> UV-A -> UV-B ->UV-C (260 nm)Visible light -> UV-A -> UV-B ->UV-C (260 nm)

The maximum DNA absorption corresponds to the The maximum DNA absorption corresponds to the wavelength of UV-C (but sunlight mostly provides wavelength of UV-C (but sunlight mostly provides UV-A radiationUV-A radiation

Synergistic EffectsSynergistic Effects

1997 EAWAG Study examined 1997 EAWAG Study examined effects of radiation and temperatureeffects of radiation and temperature

Conclusions:• Between 12 and 40° C, inactivation of bacteria is mostly due to irradiation

•Inactivation in dark control at is due to heat

•Inactivation in transparent tubes at 50° C show a combined effect of thermal and radiation

Coliphage f2 Bacteria Coliphage f2 Bacteria ResultsResults

Rotavirus ResultsRotavirus Results

Limitations of SODISLimitations of SODIS

Weather Conditions need to be rightWeather Conditions need to be right Only feasible for small volumes of Only feasible for small volumes of

waterwater Bottle restrictionsBottle restrictions Not effective against all types of Not effective against all types of

waterborne diseasewaterborne disease Turbidity is a problemTurbidity is a problem Possibilities for misusePossibilities for misuse

ClimateClimate

2 days exposure 2 days exposure

for 50-100% coverfor 50-100% cover

Doesn’t work whenDoesn’t work when

there is rainthere is rain

Central regions Central regions

more favorablemore favorable

Can SODIS provide enough Can SODIS provide enough clean water for a household?clean water for a household?

Would require 10 2-liter bottles of Would require 10 2-liter bottles of clean water per dayclean water per day

How would you prepare for rainy How would you prepare for rainy days if you don’t know when they are days if you don’t know when they are coming?coming?

Is it wise to rely on the weather? Is it wise to rely on the weather?

Water Depth in BottleWater Depth in Bottle Water depth should be as low as possible for Water depth should be as low as possible for

maximum radiation and heating.maximum radiation and heating.

Should not exceedShould not exceed10 cm10 cm

SODIS bagsSODIS bags

Bottle AgingBottle Aging

Aging of PET bottles leads to a Aging of PET bottles leads to a reduction of U.V transmittancereduction of U.V transmittance

--ScratchesScratches

-Photochemical-Photochemical

reactionsreactions

What is UV treatment effective What is UV treatment effective against?against?

Bacteria: E. Bacteria: E. colicoli, Vibrio , Vibrio choleraecholerae, , Salmonella Salmonella paratyphiparatyphi, and others, and others

Viruses: Bacteriophages, rotavirusViruses: Bacteriophages, rotavirus

Not Effective Against:Not Effective Against:

Chemically contaminated watersChemically contaminated waters

Spore and cyst forming organisms Spore and cyst forming organisms such as protozoasuch as protozoa– Giardia and CryptosporidiumGiardia and Cryptosporidium

Possibilities for MisusePossibilities for Misuse

Bottles exposed to sun in morning, but Bottles exposed to sun in morning, but in the shade after a couple of hoursin the shade after a couple of hours

Some users put the bottles on chairs, Some users put the bottles on chairs, not considering that the back of the not considering that the back of the chair casts a shadowchair casts a shadow

Bottles placed with painted side upBottles placed with painted side up Partially filled bottlesPartially filled bottles Recontamination!Recontamination!

Implementing SODIS Implementing SODIS in in

UzbekistanUzbekistan

JDA International, Inc.JDA International, Inc.

BackgroundBackgroundClimate and TopographyClimate and Topography

In April 2001, JDA (Joint Development Associates) In April 2001, JDA (Joint Development Associates) started the SODIS pilot project in the Ferghana started the SODIS pilot project in the Ferghana valley near the city of Kokand in Uzbekistan. valley near the city of Kokand in Uzbekistan.

Uzbekistan lies on the 41Uzbekistan lies on the 41stst parallel in Central Asia. parallel in Central Asia. The country is characterized by deserts, semiarid The country is characterized by deserts, semiarid steppes, vast plains. The climate in the valley can steppes, vast plains. The climate in the valley can be described as arid. The winters are cold and be described as arid. The winters are cold and summers are hot. Between April and September summers are hot. Between April and September there is virtually no precipitation or cloud coverage there is virtually no precipitation or cloud coverage (300 days sunshine/year) and abundant solar (300 days sunshine/year) and abundant solar radiation (averaging 200 kW/m2 between May to radiation (averaging 200 kW/m2 between May to September).September).

Uzbekistan seems to be a prime location to Uzbekistan seems to be a prime location to implement SODISimplement SODIS

BackgroundBackgroundSocial HistorySocial History

Economical StatusEconomical Status Post-Soviet Union economic systemPost-Soviet Union economic system

– Collective farms were privatizedCollective farms were privatized– Government took care of people’s needs. Individual initiativeGovernment took care of people’s needs. Individual initiative– and responsibility were neither asked for nor encouraged.and responsibility were neither asked for nor encouraged.– Little experience in decentralized decision makingLittle experience in decentralized decision making

The water systemThe water system– Aging and leakingAging and leaking– Depended on external Soviet bureaucracy for maintenanceDepended on external Soviet bureaucracy for maintenance– Who built quite an advanced system for the time: deep wells, Who built quite an advanced system for the time: deep wells,

water towers, pipingwater towers, piping– Lack of training and funding for proper maintenance and Lack of training and funding for proper maintenance and

operation by local Uzbek staff. Currently maintained on the operation by local Uzbek staff. Currently maintained on the village scale.village scale.

– Has contamination issues (backflow, intermittency, and leakage).Has contamination issues (backflow, intermittency, and leakage).– Little capital available because of lack of usage fees.Little capital available because of lack of usage fees.– Need for low-cost disinfectionNeed for low-cost disinfection

BackgroundBackgroundSocial History cont…Social History cont…

Cold water problemCold water problem– Because of history of waterbourne Because of history of waterbourne

diseases with water supply, most people diseases with water supply, most people boil water or drink tea. Cold water boil water or drink tea. Cold water associated with disease.associated with disease.

– In summertime, people sometimes drink In summertime, people sometimes drink contaminated water straight from the tap contaminated water straight from the tap to cool off and get reinforcing the to cool off and get reinforcing the perception.perception.

– Thus SODIS was called “sun-boiled water”Thus SODIS was called “sun-boiled water”

What was doneWhat was done

PromotersPromoters– 10 local people were trained in the SODIS method. Encouraged 10 local people were trained in the SODIS method. Encouraged

to drink SODIS water. Employed by JDA to promote its use to to drink SODIS water. Employed by JDA to promote its use to others. Divided into 3 teams. 15 villages were targeted for the others. Divided into 3 teams. 15 villages were targeted for the SODIS campaignSODIS campaign

– Approaches used:Approaches used: Mystical approach: SODIS – a type of healing water!Mystical approach: SODIS – a type of healing water! rational approachrational approach: : Emphasized strongly that drinking SODIS water Emphasized strongly that drinking SODIS water

prevents disease saves healthcare costs. Money!prevents disease saves healthcare costs. Money!– The relational approachThe relational approach: : emphasized good relationships with emphasized good relationships with

decision-makers and key people who they introduced the decision-makers and key people who they introduced the method to.method to.

Marketing schemesMarketing schemes– SODIS game, poster, brochures (highly efficient due to high SODIS game, poster, brochures (highly efficient due to high

literacy rates)literacy rates) Never promoted as cold water but as “sun boiled water” to Never promoted as cold water but as “sun boiled water” to

keep in line with cultural preferences.keep in line with cultural preferences.

ResultsResults

SODIS promotion project appears to SODIS promotion project appears to be effective. Most people introduced be effective. Most people introduced will continue to use itwill continue to use it

Source: “Bottles in the Sun”, JDA report: 2001. http://www.sodis.ch/files/MaterialsJDA/Report_2001_e.pdf

Results 2003 IResults 2003 I

Impact of SODIS on healthImpact of SODIS on health

Results 2003 IIResults 2003 II

Conclusion: Most villages saw a decrease 2/3 decrease in disease incidence after SODIS implementation.

ResourcesResources http://http://www.sodis.chwww.sodis.ch http://www.jdainternational.org/http://www.jdainternational.org/ Weglin M. et al. Solar water disinfection: scope of the process and Weglin M. et al. Solar water disinfection: scope of the process and

analysis of radiation experiments. J Water SRT-Aqua. Vol. 43 No. 3. analysis of radiation experiments. J Water SRT-Aqua. Vol. 43 No. 3. 1994.1994.

http://http://www.grilink.org/ibsrepor.htmwww.grilink.org/ibsrepor.htm http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=

348911348911

http://www.wpi.edu/Pubs/ETD/Available/etd-0423103-12424http://www.wpi.edu/Pubs/ETD/Available/etd-0423103-124244/unrestricted/rojko.pdf4/unrestricted/rojko.pdf

http://www.cdc.gov/safewater/manual/alt_water.htmhttp://www.cdc.gov/safewater/manual/alt_water.htm

http://http://solarcooking.org/sunandwater.htmsolarcooking.org/sunandwater.htm