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Filtrate from spiked laboratory efficacy tests was negative for E. coli presence for all E. coli doses and all sample times (Table 1). This represents up to >9-log E. coli removal efficiency. Results are consistent with other spiked water laboratory tests that demonstrated >9-log bacteria removal within the first liter of flow through new PointONE™ filters (Erikson et al. 2013).

Table 1

Water quality test results for Sawyer PointONE™ filter performance in the laboratory (laboratory efficacy), controlled field testing (field efficacy) in Maine and Honduras, and in Honduran homes (field effectiveness)

Water sourceParameterSource geometric mean (95% CI)Filtrate geometric mean (95% CI)% Reduction in geometric meanp-valuea
Laboratory spiked water E. coli (CFU/100 mL)b 107–109 <1 >99.99999% – 
Urban stream in Maine (n = 5) E. coli (MPN/100 mL) 186 (139, 249) <1 >99.7% <0.001 
Total coliform (MPN/100 mL) >2,420c <1 >99.98% <0.001 
Turbidity (NTU)d – – – – 
River water in Honduras (n = 5) E. coli (MPN/100 mL) 124 (79.9, 192) 0.57 (0.44, 0.75) 99.5% <0.001 
Total coliform (MPN/100 mL) >2,420 1,921 (1,530, 2,414) e 0.12 
Turbidity (NTU) 5.9 (5.0, 8.8) 0.33 (0.24, 0.45) 94.3% 0.001 
Honduran households (n = 50) 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) 1,677 (1,382, 2,036) 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 
Water sourceParameterSource geometric mean (95% CI)Filtrate geometric mean (95% CI)% Reduction in geometric meanp-valuea
Laboratory spiked water E. coli (CFU/100 mL)b 107–109 <1 >99.99999% – 
Urban stream in Maine (n = 5) E. coli (MPN/100 mL) 186 (139, 249) <1 >99.7% <0.001 
Total coliform (MPN/100 mL) >2,420c <1 >99.98% <0.001 
Turbidity (NTU)d – – – – 
River water in Honduras (n = 5) E. coli (MPN/100 mL) 124 (79.9, 192) 0.57 (0.44, 0.75) 99.5% <0.001 
Total coliform (MPN/100 mL) >2,420 1,921 (1,530, 2,414) e 0.12 
Turbidity (NTU) 5.9 (5.0, 8.8) 0.33 (0.24, 0.45) 94.3% 0.001 
Honduran households (n = 50) 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) 1,677 (1,382, 2,036) 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 

CFU, Colony forming unit; MPN, Most probable number; NTU, Nephelometric turbidity units.

ap-values calculated with paired t-tests on log-transformed values.

bSpiked tests at 107, 108, 109 CFU/100 mL. Filtrate samples collected at three times (first 100 mL, after 500 mL, after 1,000 mL of flow).

cUpper detection limit: 2,420 MPN/100 mL.

dNo turbidity data available for Maine control testing.

eTotal coliform percent reductions limited by test results at the upper detection limit.

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