Ceramic Filter for Small System Drinking Water Treatment: Evaluation of Membrane Pore Size and Importance of Integrity Monitoring

Ceramic filtration has recently been identified as a promising technology for drinking water treatment in households and small communities. This paper summarizes the results of a pilot-scale study conducted at the U.S. Environmental Protection Agency’s (EPA) Test & Evaluation (T&E) Facility in Cincinnati on two ceramic filtration cartridges with pore sizes of 0.05 and $0.01\mu \text{m}$ to evaluate their ability to remove turbidity and microbiological contaminants such as bacteria [Bacillus subtilis $\left(\approx 1.0\mu \text{m}\right)$ and Escherichia coli $\left(\approx 1.4\mu \text{m}\right)$ ], Cryptosporidium oocysts $\left(4–6\mu \text{m}\right)$ , polystyrene latex (PSL) beads $\left(2.85\mu \text{m}\right)$ (a surrogate for Cryptosporidium), and MS2 bacteriophage $\left(\approx 0.02\mu \text{m}\right)$ (a surrogate for enteric viruses). The results demonstrated that the relatively tighter $0.01\text{-}\mu \text{m}$ cartridge performed better than the $0.05\text{-}\mu \text{m}$ cartridge in removing all the biological contaminants and surrogates. For turbidity removal, the $0.01\text{-}\mu \text{m}$ cartridge performed slightly better than the $0.05\text{-}\mu \text{m}$ cartridge; however, the permeate rate in the $0.01\text{-}\mu \text{m}$ cartridge reduced rapidly at higher feed water turbidity levels indicating that a tighter membrane should only be used with adequate pretreatment or at a low feed water turbidity to prolong membrane life. Microbiological monitoring was identified as a more sensitive indirect integrity monitoring method than turbidity and particle count monitoring to ensure effective treatment of water by ceramic filtration. Both PSL beads and B. subtilis showed potential as effective surrogates for Cryptosporidium, with B. subtilis showing higher degree of conservatism. Any opinions expressed in this article are those of the writer(s) and do not necessarily reflect the official positions and policies of the EPA. Any mention of products or trade names does not constitute recommendation for use by EPA. This document has been reviewed in accordance with EPA’s peer and administrative review policies and approved for publication.