Removal of virus-sized particles and Escherichia coli by the Potters for Peace ceramic water filter

The Potters for Peace ceramic water filter, the Filtron, is a point-of-use drinking water treatment device that has been used in developing communities since 1998. The ceramic water filter is a colloidal-silver lined permeable ceramic water filter. Despite being widely used in a number of countries, the pathogen removal characteristics have not been well documented.;This research studied the removal of virus sized particles, which are smaller than typical pore sizes of the filter. Validation of the removal effectiveness will assist in determining the ceramic water filters' success as a point-of-use water treatment technology. It was found that the ceramic water filter has the capacity to remove fluorescent carboxylate-coated polystyrene microspheres which served as surrogates for viruses, bacteria, and protozoans. Removal of virus-sized microspheres with diameters of 0.02 and 0.10 mum ranged from 62.5% to 99.6% in the six filters tested. There was improved removal for the larger particles with diameters of 0.50 to 4.5 mum which ranged from 98.6% to 99.92%.;In addition to the physical removal (sedimentation and filtration), the inactivation of bacteria by the colloidal silver was also investigated by using E. coli as a surrogate for bacteria. Disinfection of E. coli by filters that had been used in the field or laboratory for several years without silver addition ranged from 85.64% to 99.994%. There was improved disinfection once the filters were recoated with silver which ranged from 99.7% to 99.995%. Once the silver concentrations had stabilized the disinfection ranged from 91.63% to 99.88%. All of the filters tested achieved greater than a 3 log removal directly after recoating with silver. It was found that the colloidal silver assists in the inactivation of E. coli bacteria, but this effect is significant and reliable across filters only at high concentrations achieved directly after coating with silver. After the silver concentrations had stabilized at lower levels the E. coli removal was similar to before recoating with silver. Tests also showed that after sequential batches of water containing high concentrations of E. coli were treated by the filters, the filters could contribute bacteria into clean water thus increasing bacterial growth.