40 CFR §141.552

1. (a)If your system consists of alternative filtration(filtration other than slow sand filtration, diatomaceous earth filtration, conventional filtration, or direct filtration) you are required to conduct a demonstration (see tables in § 141.551). Your system must demonstrate to the State, using pilot plant studies or other means, that your system's filtration, in combination with disinfection treatment, consistently achieves:
   1. (1)99 percent removal of Cryptosporidium oocysts;
   2. (2)99.9 percent removal and/or inactivation of Giardia lamblia cysts; and
   3. (3)99.99 percent removal and/or inactivation of viruses.
2. (b)[Reserved]