Removal of virus to protozoan sized particles in point-of-use ceramic water filters

The particle removal performance of point-of-use ceramic water filters (CWFs) was characterized in the size range of 0.02-100 μm using carboxylate-coated polystyrene fluorescent microspheres, natural particles and clay. Particles were spiked into dechlorinated tap water, and three successive water batches treated in each of six different CWFs. Particle removal generally increased with increasing size. The removal of virus-sized 0.02 and 0.1 μm spheres were highly variable between the six filters, ranging from 63 to 99.6%. For the 0.5 μm spheres removal was less variable and in the range of 95.1-99.6%, while for the 1, 2, 4.5, and 10 μm spheres removal was >99.6%. Recoating four of the CWFs with colloidal silver solution improved removal of the 0.02 μm spheres, but had no significant effects on the other particle sizes. Log removals of 1.8-3.2 were found for natural turbidity and spiked kaolin clay particles; however, particles as large as 95 μm were detected in filtered water.