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Laboratory Efficacy and Field Effectiveness of Hollow Membrane Fiber Microfilters Used for Household Water Treatment in Honduras
Anna Murray, Barbara Stewart, Catherine Hopper, Ellen Tobin, Jimmy Rivera, Henri Mut-Tracy, Patrick Stewart, Cordelia Stewart,
Claire Tobin, Mario Goeb, Carolyn Meub, Daniele Lantagne
Overview
• Background• Sawyer PointONE™ Filter• Study Rationale
• Study Design and Methods• Results
• Laboratory Efficacy• Field “Controlled” Efficacy – Maine/Honduras• Household Effectiveness
• Summary • Future Research
Sawyer PointONE™ Filter
Filter Assembly
• Distributed in over 70 countries for emergency relief, HWT
• Advertised lifespan of up to 10 years
Sawyer PointONE™ Filter
Filter
Image modified from: http://sawyer.com/international/saving-lives/our-technology/
0.1 µm hollow fiber membrane
Backwashing required periodically to maintain
Sawyer PointONE™ Filter
Existing Evidence
• Laboratory Efficacy (Hydreion, 2005; Erikson et al., 2013)
– >6-log reduction of bacteria
– >5-log reduction of protozoan cysts
• Health Impact Trial (Lindquist et al, 2014)
– 79% diarrheal disease prevalence reduction in children under 5 after 3 months
• Microbiological Field Effectiveness– Grey literature has shown bacterial contamination in tested filtrate
(18-54% of samples in 3-month to 3-year follow-up)
– We did not find published data with quantitative microbiological results
Study Rationale
• Pure Water for the World (PWW) installed over 250 filters in six rural Honduran communities between 2010-2013
• Internal follow-up identified high rate of abandoned and broken filters (up to 50%)
• Evidence of membrane fouling after 2 years (Murray et al., 2015)
• Lack of available robust field effectiveness data
• Desire to understand the performance of the Sawyer PointONE™ filter in household settings
Trojes
1) Laboratory Efficacy Testing
E. coli removal testing on new filter in UMaine laboratory
2) Field “Controlled” Efficacy Testing
Microbiological testing on new filter in the field
• Maine urban stream
• Honduran river water
3) Household Effectiveness Testing
Microbiological water quality testing in two Honduran communities
• Community 1: 23 filters after 3 years of use
• Community 2: 27 filters after 1 year of use
Study Design
Spring 2014
Summer 2014
August 2014
• New PointONE™ filter
• Spiked 1.2 L water with 107, 108, 109 CFU/100 mL E. coli
• Three filtered samples collected: – first 100 mL– after 500 mL– after 1000 mL
• Processed by membrane filtration with m-ColiBlue24® media to enumerate E. coli
• Backwashed filter 3x between each test
Methods
1) Laboratory Efficacy Testing
• New PointONE™ filter
• Microbiological tests of river water in Maine and Honduras (5 locations on each river)
• E. coli, Total Coliform, and Turbidity for source and filtrate
• For each test:– Backwashed filter 3x– Filled source bucket with water– Flowed for 1 min– Collected filtered sample– Processed samples by IDEXX most probable
number method (MPN)
Methods
2) Field “Controlled” Efficacy Testing
• 50 Households in two communities– Received filters and training 1 or 3 years prior
• E. coli, Total Coliform, and Turbidity for source and filtrate
• At each household:– Household member backwashed filter– Filled source bucket with water– Flowed for 1 min– Collected filtered sample– Collected unfiltered sample– Measured flow rate– Processed samples by IDEXX most probable
number method (MPN)
Methods
3) Household Effectiveness Testing
Parameter
Source Geometric Mean
(95% CI)
Filtrate Geometric Mean
(95% CI)
% Reduction in Geometric
Mean p-value
E. coli (CFU/100 mL) 107, 108, 109 < 1 >99.99999% -
Results
1) Laboratory Efficacy Testing
• Removed all detectable E. coli in laboratory tests
Parameter
Source Geometric Mean
(95% CI)
Filtrate Geometric Mean
(95% CI)
% Reduction in Geometric
Mean p-value*
E. coli (MPN/100 mL) 186 (139, 249) < 1 >99.7% <0.001
Total Coliform (MPN/100 mL) >2420 < 1 >99.98% <0.001
E. coli (MPN/100 mL) 124 (79.9, 192) 0.57 (0.44, 0.75) 99.5% <0.001
Total Coliform (MPN/100 mL) >2420 1921 (1530, 2414) >20.6 % ** 0.12
Turbidity (NTU) 5.85 (3.98, 8.79) 0.33 (0.24, 0.45) 94.3% 0.001
Results
* paired t-test on log transformed values** greater percent reduction, because source is at upper detection limit
2) Field “Controlled” Efficacy Testing (N=5 Maine, N=5 Honduras)
Mai
ne
Ho
nd
ura
s
• Removed all detectable E. coli and total coliform in Maine tests
• Removed almost all E. coli in Honduras tests, but not significant reduction of total coliform
Parameter
Source Geometric Mean
(95% CI)
Filtrate Geometric Mean
(95% CI)
% Reduction in Geometric
Mean p-value*
E. coli (MPN/100 mL) 48.9 (32.7, 72.9) 5.1 (2.9, 9.0) 89.5% <0.001
Total Coliform (MPN/100 mL) 1677 (1382, 2036) 539 (352, 824) 67.9% <0.001
Turbidity (NTU) 5.4 (3.7, 8.0) 0.60 (0.46, 0.79) 88.9% <0.001
Results
* paired t-test on log transformed values
3) Household Effectiveness Testing (N=50)
• Significant reduction of E. coli, total coliform, and turbidity in households
• < 90% reduction in all parameters, 30% comply with WHO Standard (<1 E. coli)
• Average Flow rate: 77.2 mL/min (expected: 719 mL/min)
Source Geometric Mean (95% CI)
(MPN/100 mL)
Filtrate Geometric Mean (95% CI)
(MPN/100 mL)
% Reduction in Geometric
Mean
1) Laboratory 107, 108, 109 < 1 >99.99999%
2) Maine river (n=5) 186 (139, 249) < 1 >99.7%
Honduras river (n=5) 124 (79.9, 192) 0.57 (0.44, 0.75) 99.5%
3) Households (n=50) 48.9 (32.7, 72.9) 5.1 (2.9, 9.0) 89.5%
Results
• Very high performance in laboratory and controlled field testing
• Comparatively lower performance in households
• Newer and uncracked filters better odds reaching 90% reduction
• User backwashing (correct demonstration) did not change odds of reaching 90% reduction
E. Coli Summary
• New filters demonstrated very good E. coli removal performance in
laboratory and controlled field testing
– Unknown why total coliform removal was incomplete in Honduras
“controlled” testing
• Filters in households improved water quality; however:
– Flow rates were slow (11% of expected)
– Performance not as high as that of new filters
– Up to half of filters had been abandoned in one community
– Seven filters (18%) had higher E. coli concentrations in filtrate than in source
water
– In one community (3 yr), 6 of the 23 tested filters had observable cracks or
leaks
– Do not know the reason for incomplete E. coli removal in some households
– Total coliform reduction was lower than expected in household effectiveness
testing
Summary
Limitations
• Small sample size in household testing
• Household level E. coli contamination lower than in efficacy tests – Harder to detect larger % reduction
• Selection Bias?– Excluded households with missing, completely failed, or abandoned filters
• Limited household demographic information
Future Research
• Confirm quantitative microbiological field effectiveness results over long-
term follow-up with larger sample size
• Understand discrepancy between new and used filter performance, partial
total coliform removal in field testing, and potential PointONE™ failure
mechanisms
Future Research
Acknowledgements
• Water For ME Foundation
• Pure Water for the World
• University of Maine
• Bangor High School STEM Academy
• Tufts University
Thank you!
References
• Hydreion 2005 Microbiological Testing of the Sawyer 7/6B Filter, Safety Harbor, FL, USA. [online] www.sawyer.com/documents/field-micro.pdf.
• Erikson, J., Veazey, J., Ritenour, L., Ross, H., Robitaille, S., Rossomme, E. 2013 Microbiological Testing of the Sawyer Bucket Filter. Messiah College, Mechanicsburg, PA, USA. [online] https://sawyer.com/wp-content/uploads/2013/12/Sawyer_Testing_Bucket.pdf.
• Lindquist, E.D., George, C.M., Perin, J., Neiswender de Calani, K.J., Norman, W.R., Davis, T.P., Perry, H. 2014 A Cluster Randomized Controlled Trial to Reduce Childhood Diarrhea Using Hollow Fiber Water Filter and/or Hygiene-Sanitation Educational Interventions. The American journal of tropical medicine and hygiene. 91, 190–197.
• Brune, L., Lee, A., Moreno, J., Restrepo, C., Travis, E., Nunez, J., Linden, K. 2013 Monitoring and Evaluation of a Point- of- Use Water Treatment Pilot Project in the Peruvian Amazon. University of Colorado, Boulder, CO, USA.
• Goeb, M. 2013a Follow-up on Sawyer Filters in the community of San Francisco de las Quebradas, Trojes, Honduras. Pure Water for the World, Rutland, VT, USA. [online] http://purewaterfortheworld.org/pdf/San%20Francisco%20follow-up%202013.pdf.
• Kohlitz, J., Hasan, T., Khatri, K., Sokota, A., Iddings, S., Bera, U., Psutka, R. 2013 Assessing reported use and microbiological performance of a point-of-use household water filter in rural Fiji. Journal of Water, Sanitation and Hygiene for Development. 3, 207.
• Murray, A., Goeb, M., Stewart, B., Hopper, C., Peck, J., Meub, C., Asatekin, A., Lantagne, D. 2015 Fouling in hollow fiber membrane microfilters used for household water treatment. Journal of Water, Sanitation and Hygiene for Development. 5, 220-228.
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• Peletz, R., Simunyama, M., Sarenje, K., Baisley, K., Filteau, S., Kelly, P., Clasen, T. 2012 Assessing water filtration and safe storage in households with young children of HIV-positive mothers: a randomized, controlled trial in Zambia. PloS one. 7, e46548.
• Rosa, G., Majorin, F., Boisson, S., Barstow, C., Johnson, M., Kirby, M., Ngabo, F., Thomas, E., Clasen, T. 2014 Assessing the Impact of Water Filters and Improved Cook Stoves on Drinking Water Quality and Household Air Pollution: A Randomised Controlled Trial in Rwanda. PLoS ONE. 9, e91011.
