INDEPENDENT EVALUATION OF THE BIOSAND WATER FILTER IN
RURAL CAMBODIA: SUSTAINABILITY, HEALTH
IMPACT AND WATER QUALITY
Kaida Liang
Background of BSF in Cambodia• Widespread lack of safe drinking
water– Microbiological and chemical
contamination – Rural households lack access
to a conventional water treatment system
• BSFs introduced (1999-pilot)– Hagar and Cambodia Global
Action (CGA) implementing BSF projects
– Supported by Samaritan’s Purse (SP) and the Canadian International Development Agency
BSF projects
What has happened with the 20,000+
biosand filters introduced in Cambodia?
343982
Study Objectives
Assess the following parameters and indicators:
i. sustainability: continued use of previously installed filters over time
ii. water quality: microbiological effectiveness in situ of the filters still being used
iii. health impact: a prospective cohort study in which diarrheal disease incidence is measured among people in filter (intervention) households versus people in matched non-filter, control households
Household Enrollment
21 000 + Households
175 Randomly Selected CGA HouseholdsCGA
175 Randomly Selected Hagar Households
336 Households
51 CGA Intervention Households(2 households quit study)
53 Hagar Intervention Households(2 households quit study)
53 Hagar Control Households
51 CGAControl Households
Longitudinal Prospective Cohort Study
Cross Sectional Study
Data Collection
• Cross-sectional - visit of 336 households who had a BSF between 0.5-8 years
• Longitudinal - monthly visits to over 200 households (Jan-May 2007) – 50 intervention households from each
organization (Hagar, CGA) and 100 matched control households
• Water quality - monthly sampling of raw, treated and stored water– Test for E. coli and turbidity reductions
Data Analysis• Cross-sectional survey
– Examined relationship between continued use and household water and sanitation practices
• Longitudinal prospective cohort– Examined water quality
improvements – Measured relationship
between filter use and reduced diarrhea cases across age cohorts via odds ratios (OR)
Cross-sectional Survey Results• 336 households enrolled in survey• 294 (87.5%) households reported still using the BSF• Average time in use 2.5 years; some in use for 8 years
05
1015
Per
cent
0 5 10 15time_use
Risk Factors for Sustained Use
• Factors associated with continued BSF use: OR (95% CI)– Receiving training: 2.04 (1.0-3.9)– Method of drawing water (using a dipper): 3.1
(1.6-6.1)– Deep well for water source: 2.6 (1.3-5.4)
• Factors associated with discontinued BSF use: – Boiling water 0.07 (0.02 - 0.3)
Longitudinal Study Results: Water quality
• Filters reduce E. coli concentrations in treated water by a mean of 95% (1.3 log10 reduction value)– Up to 4 log (99.99%) observed
• 55% of effluent water samples from filters were <10 E. coli/100ml (low risk)
• 82% reduction of turbidity from untreated to treated water
Diarrhea disease reductions
0
0.05
0.1
0.15
0.2
0.25
0 1 2 3 4 5 6Household visit
Case
s/pe
rson
wee
k
BSF Households
Control
Longitudinal Study: Health
• Filters associated with a mean 44% reduction in diarrheal disease in users versus non users (OR=0.56, 95% CI 0.49-0.66)
• Group experiencing most protective effect, ages 2-4 (46% reduction for filter users)
• No significant protective effect for ages 0-2 (OR=0.89, 95% CI 0.6-1.2)– Southeast Asia children typically not weaned until
ages 2-3; so probably not/less exposed to filtered water
Conclusions• BSFs have sustained use in Cambodia• Filters improved water quality (1.3 log10 or
95% reduction of E. coli in raw water) and reduced diarrheal disease (44% compared to matched non-filter households)
• Diarrhea reductions comparable to other HWTS interventions
• Need to prevent recontamination through appropriately designed software (behaviors) and hardware (containers)
AcknowledgementsI would like to gratefully acknowledge the support and contribution of:
• Project staff: Proum Sorya, Van Sokheng, Oum Sopharo, Song Kimsrong, Uon Virak, Little Sokheng, Ken Sreymom, Monn Pong, Seiha, Um Saravuth
• Royal Government of Cambodia, Ministry of Rural Development – Dr.Mao Saray & Mr.Chea Samnang
• Hagar and CGA Program Managers, Mr.Yim Viriya & Mr.Me Kosal• WSP (World Bank) – Mr.Jan Willem Rosenboom, • Plan International - Mr.Peter Feldman• USAID – Dr.John Borrazzo• WHO SE Asia – Dr.Terrence Thompson • Samaritan’s Purse Canada (John Clayton, Andrew Buller, Marianne
Maertens)• Dr.Mickey Sampson - RDI-C, • Dr.Mark Sobsey, Douglas Wait, Dr.Joe Brown, Dr.Christine Stauber,
Dr.Kimberly Blauth, Mark Elliott and the Sobsey lab group
Questions?