Six-month field monitoring of point-of-use ceramic water filter by using H₂S paper strip most probable number method in San Francisco Libre, Nicaragua

Abstract

Monitoring programs are an essential concomitant to household drinking water treatment. The author implemented a 6-month monitoring program to assess the performance of the Potters for Peace (PFP) water filter in San Francisco Libre, Nicaragua. Both analytical methods and surveys were used to study flow-rate, microbiological removal and user acceptance of 100 PFP filters. Results for the 6-month monitoring by using hydrogen sulfide (H2S) Paper Strip Most Probable Number (H2S MPN) showed that an average of 80.4% of the sample population had less than 2.2 H2S producing colonies per 100 mL after filtration through the PFP filter. Six percent of the visited households had more than 16 CFU/100 mL after filtration. Over the 6 months of the study, the level and pattern of contamination did not change significantly. Filtration rate measurements showed that the average PFP flow-rate was 1.7 L/hrs. Membrane Filtration with mColiBlue24® tests were conducted for half of the sample population in the final month of the study. Total Coliform results showed that 30.6% of the studied families had less than 2.2 CFU/100 mL, and 27% had 0 CFU/100 mL for E-coli when initially present. Approximately 45% of the households had more than 16 CFU/100 mL after filtration for Total Coliform. Yet even so average removal rates for the PFP filter overall were 97.6% for E-coli and 89.3% for Total Coliforms. Users mainly complained about the filter's small capacity (20L), and they requested a ceramic instead of a plastic recipient vessel. Filter breakage was appreciable, since 15% of the filters broke by the end of the study. Recontamination of filtered water due to contaminated receptacles was in 33% of cases. Multiple barrier solutions, such as chlorination after filtration, are recommended for PFP filter users. The H2S MPN method's relevance for long-term monitoring programs in developing countries is evaluated in this report. The use of H2S MPN is recommended for rural areas where there are cost constraints in conjunction with a validation system. Validation of H2S MPN may be given by performing parallel tests with other Standard Methods, such as Membrane Filtration (MF). The report also includes a discussion of lessons learned and recommendations for future monitoring programs of household drinking water systems.