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WWT Regulations & NPDES ComplianceIntermediate 14 min read

Illinois Wastewater Treatment: Classification Groups & the MWRD Deep Tunnel

How Illinois's Class 1-4 wastewater operator system maps to facility complexity, and why Chicago-area operators need to understand the Metropolitan Water Reclamation District's Tunnel and Reservoir Plan.

Illinois Wastewater Treatment Operator Certification
Classification Structure
Illinois EPA certifies wastewater treatment operators into four classes, with Class 1 as the highest classification and Class 4 as entry-level — the reverse numbering from some states' systems, so don't assume 1 = entry:
  • Class 4 — minimum for Group 4 facilities: lagoon treatment systems.
  • Class 3 — minimum for Group 3 facilities: fixed film processes, Imhoff tank systems under 1.0 MGD, and all primary treatment systems.
  • Class 2 — minimum for Group 2 facilities: activated sludge systems under 1.0 MGD design average flow (DAF).
  • Class 1 — minimum for Group 1 facilities: all domestic wastewater systems 1.0 MGD DAF or more (excluding lagoons and primary-only systems).
Certificates are valid for 3 years. Class 1 and 2 operators must complete 30 continuing education hours (minimum 2

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