Ill. Admin. Code tit. 35, § 391.501
a) Permit applications, except water treatment plant sludge application projects, shall provide analyses for the following parameters;
c) Wastewater treatment plants whose design population equivalents are less than 1000, which have sanitary sewers not subject to large inflow sources and do not receive any industrial process wastewater may request an exemption from analyzing the metals under Subsection 391.501 (a) (3) except for cadmium which must always be analyzed. These generators shall periodically analyze their sludge used for land application and make the necessary calculations for nutrient and heavy metal loadings in accordance with the following schedule:
| Design Population Equivalents | Frequency of Sludge Analysis |
| >100,000 | Monthly |
| 10,000-100,000 | Quarterly |
| 1000-9999 | Semi-annual |
| <1000 | Annual |
d) Water treatment plant sludge permit applications shall provide analyses for the following parameters: