Effects of Chlorination on Silver-Coated Ceramic Pot Filters (CPFs)

It has been suggested that the absence of residual protection against recontamination is a potential weakness of ceramic pot filters (CPFs). As a result, and against CPF manufacturers' recommendations, users may routinely apply bleach to CPFs as a way to prevent recontamination. Concerns regarding the potential repercussions on the CPFs' ability to disinfect water and/or their lifespan due to an interaction between chlorine and silver, as well as the health risks associated with chlorine poisoning and chlorination disinfection by-products (DBPs) exist. This preliminary study evaluated the effects of chlorination on silver-coated CPFs, manufactured and used in Guatemala, in terms of disinfection effectiveness and performance. Three scenarios including no chlorine dosing and high and low frequency chlorine dosing were used during the laboratory and field experimentation phases. Additionally, an assessment of CPF users' application of bleach was performed by interviewing rural families in Guatemala. The limited laboratory and field experimentation showed that the disinfection effectiveness of silver-coated CPFs will not be affected by bleach application to the untreated water. CPFs used during both phases of this study remained effective in removing bacteria at logarithmic reduction values (LRVs) ranging from 0.3 to 2.6 for E. coli and 0.7 to 3.0 for total coliforms. However, the lifespan of the CPFs might be negatively affected by this practice as there appears to be a relationship between bleach application, silver concentration, and flow rate performance. Additionally, high residual chlorine concentrations in the filtered water could potentially have adverse health effects on CPF users.