35 Ill. Adm. Code 370.1110
Type
Section 370
Section 370.1110 Type
a) Granular media filtration is considered to include the
following type units:
1) High rate single, dual and multi-media of either the pressure
or gravity type with facilities for backwashing.
2) Low rate sand filters dosed intermittently or periodically.
b) Low rate filtration is generally limited in use to small
installations.
c) For miscellaneous considerations, refer to Section 370.203(j).