 |
Safe Water System (SWS) - What Do We Know About the
Safe Water System? |
|
|
| Safe Water Home
> About
> Know?
|
|
The SWS improves
microbiologic drinking water quality.
The following results are from studies
conducted by the CDC and our partners to document
reduction of microbiological indicators (fecal/thermotolerant
coliforms, and E. coli) in users of the Safe Water
System.
| Study Country |
Results |
Reference |
| Bolivia |
Fecal coliforms were found in water from 39
(93%) of 42 wells and 33 (79%) of 42 usual home
water vessels. Escherichia coli was isolated
from water samples from 37 (88%) of 42 wells
and 29 (69%) of 42 usual home water vessels.
During the intervention phase, SWS users (chlorine
and vessel) had substantially lower geometric
mean fecal coliform colony counts (P < 0.0001)
and lower geometric mean E. coli colony counts
(P < 0.0001) than water from vessel-only
users in all sampling rounds. |
Quick
et al, 1996 
308KB
|
| Pakistan |
Baseline drinking water samples among intervention
households were contaminated with a mean 9397
cfu/100ml of thermotolerant coliforms. After
intervention the mean concentration of thermotolerant
coliforms decreased by 99.8% among the intervention
households, compared to an 8% reduction among
controls. |
Luby
et al, 2001
270KB |
| Pakistan |
At baseline, 71 of 75 stored drinking water
samples were contaminated with a median of 20,000
cfu of thennotolerant coliforms per 100 ml.
Seventy-two households (96%) accepted and continued
to use the interventions. After intervention,
36 of the 47 household (77%) who had received
the water vessel and bleach had no detectable
thermotolerant colifoms in their water. |
Luby
et al, 1998
92KB |
| Malawi |
Analysis of water samples demonstrated that
there was a 69% reduction in the geometric mean
of faecal coliform levels in household water
among the group using the improved bucket. (Note:
no chlorine was used in this study, only the
improved container). |
Roberts
et al, 2001
274KB |
Click below for a table containing data on the inactivation
of several bacteria, viruses, and protozoa by chlorine.
Effect of Chlorination
on Inactivating Selected Microorganisms
The SWS prevents diarrhea.
The following studies, conducted by CDC
and our partners, are randomized, controlled trials
that document diarrheal disease reduction in users
of the Safe Water System.
| Pakistan |
71% |
Luby et al, 2004. Delayed effectiveness of
home-based interventions in reducing childhood
diarrhea, Karachi, Pakistan. Am. J. Trop. Med.
Hyg. 71(4). |
| Zambia |
48% |
Quick
et al, 2002
114KB |
| Uzbekistan |
84% |
Semenza
et al, 1998
285KB |
| Bolivia |
44% |
Quick
et al, 1999
329KB |
Bolivia
Bangladesh |
43% reduction
24% reduction
|
M.D. Sobsey, T. Handzel and L. Venczel, Chlorination
and safe storage of household drinking in developing
countries to reduce waterborne disease. Water
Science and Technology Vol 47. |
The SWS improves the quality
of beverages sold by street vendors.
Street-vended foods and beverages, an integral
part of urban economics in the developing world,
have been implicated in cholera transmission in
Latin America. To improve the microbiologic quality
of market-vended beverages in Guatemala, the SWS,
handwashing, and education were promoted among street
vendors. We
conducted
415KB a randomized controlled intervention
trial among 41 vendors who received the intervention
and 42 control vendors, comparing total and fecal
coliform bacteria and Escherichia coli contamination
of market-vended beverages, stored water, and vendors'
hands. When compared with samples from control vendors,
a significant decrease in total coliform (P <
0.001) and fecal coliform (P < 0.001) bacteria
in samples of stored water and beverages sold by
intervention vendors was observed over the course
of the study. The vessel system was well accepted
by vendors. This simple inexpensive system consisting
of hypochlorite disinfectant, plastic vessels, soap,
and education can significantly reduce fecal contamination
of market-vended beverages.
The SWS improves the quality
of bulk oral rehydration solution (ORS).
Oral rehydration solution (ORS) is lifesaving
therapy for cholera and pediatric diarrhea. During
a cholera epidemic in Guinea-Bissau, we evaluated
the microbiologic quality of ORS prepared at a hospital
and tested a simple intervention using special vessels
for disinfecting tap water with bleach and for preparing,
storing, and dispensing ORS (Daniels,
et al, 1999
371KB ) . Few coliform bacteria and Escherichia
coli were recovered from tap water used to make
the ORS; however, mean pre-intervention counts of
coliform bacteria (3.4 X 107 colony-forming
units [cfu]/100 ml) and E. coli (6.2 X 103
cfu) decreased significantly during the intervention
period to 3.6 X 102 cfu and 0 cfu, respectively
(P < 0.001). Using bleach disinfectant and special
storage vessels prevents bacterial contamination of
ORS and reduces the risk of nosocomial transmission
of cholera and other enteric pathogens.
The SWS can be effectively
marketed.
CDC currently works with 13 Population Services
International Country programs to manufacture, distribute,
and socially market the Safe Water System sodium hypochlorite
solution product. This very successful partnership
has sold over 12 million bottles of hypochlorite solution,
specifically branded and marketed in each country.
This sales chart from our first partnership country,
Zambia, shows how social marketing and demand creation
can lead to steadily increasing sales.
Short and medium-term use
of the SWS can be enhanced by motivational interviewing.
A SWS program was initiated in Zambia with
one group receiving the standard practice of health
education (comparison group) and one group receiving
Motivational Interviewing (MI) (experimental group).
MI is a person-centered, stage-based approach to encourage
change in personal habits by resolving ambivalence
and eliciting a person's own arguments for change.
In the first field trial, the majority of users used
the system correctly (as measured by residual chlorine
present in 71.1-94.7% of the households), but no statistical
difference in usage rate was seen between the education-only
and MI groups. A second field trial incorporated lessons
learned by improving the MI training and resulted
in significantly higher purchase rates, with an average
of 0.71 more bottles per month in MI households than
education-only household, of the disinfectant in the
MI group (Thevos,
et al, 2000
170KB ) . A third field trial again improved
the MI training, and compared MI with social marketing.
Indicators of safe water practices (including residual
chlorine levels in households) and knowledge improved
dramatically in the MI group as compared to social
marketing alone (Thevos,
et al, 2000a
200KB) . Follow-up work 16 months after the
third field trial showed that the MI group still had
double the rate of correct use of the SWS as measured
by chlorine residual as the social marketing group
alone (Thevos,
et al, 2002
61KB )
. Thus, MI is a promising method for motivating the
adoption and sustained use of safe water behaviors.
Water stored in clay pots can
be effectively treated with sodium hypochlorite solution.
Ogutu
et al, 2001
212KB demonstrated that turbid, contaminated
source water stored in clay pots can be adequately
disinfected using chlorine in laboratory and household
settings.
If you have experience with any of
these or related issues, we would like to hear about
it. Please email us at safewater@cdc.gov. |
Some documents are available here in Adobe Acrobat Reader
format (PDF). To view or print them, you must have the
free Adobe Acrobat Reader installed on your computer.
Please click HERE
for more information and to download Acrobat Reader. |
|
| |
| |
|
|
|
|
|
