laboratory efficacy and field effectiveness of hollow membrane fiber microfilters used for household...
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![Page 1: Laboratory Efficacy and Field Effectiveness of Hollow Membrane Fiber Microfilters Used for Household Water Treatment in Honduras Anna Murray, Barbara Stewart,](https://reader035.vdocuments.site/reader035/viewer/2022062309/5697c0231a28abf838cd3c3a/html5/thumbnails/1.jpg)
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
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Overview
• Background• Sawyer PointONE™ Filter• Study Rationale
• Study Design and Methods• Results
• Laboratory Efficacy• Field “Controlled” Efficacy – Maine/Honduras• Household Effectiveness
• Summary • Future Research
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Sawyer PointONE™ Filter
Filter Assembly
• Distributed in over 70 countries for emergency relief, HWT
• Advertised lifespan of up to 10 years
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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
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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
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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
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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
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• 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
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• 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
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• 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
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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
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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
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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)
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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
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• 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
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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
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Acknowledgements
• Water For ME Foundation
• Pure Water for the World
• University of Maine
• Bangor High School STEM Academy
• Tufts University
Thank you!
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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.
• Ensink, J.H.J., Bastable, A., Cairncross, S. 2015 Assessment of a membrane drinking water filter in an emergency setting. Journal of water and health. 13, 362–70.
• Boisson, S., Kiyombo, M., Sthreshley, L., Tumba, S., Makambo, J., Clasen, T. 2010 Field assessment of a novel household-based water filtration device: a randomised, placebo-controlled trial in the Democratic Republic of Congo. PloS one. 5, e12613.
• 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.