CT DEEP Reissues the General Pretreatment Permit for Significant Industrial User (SIU) Discharges

The Connecticut Department of Energy and Environmental Protection (CT DEEP) has announced the reissuance of the General Pretreatment Permit for Significant Industrial User (SIU) Discharges to Publicly Owned Treatment Works (POTWs). This general permit regulates industrial wastewater discharges from facilities classified as Significant Industrial Users under the federal Pretreatment Program 40 CFR Part 403.

Note that the name of this permit has been updated – the previous version, which expired on 10/31/25, was called the General Permit for the Discharge of Wastewaters from Significant Industrial Users (SIU GP).

Who does the permit apply to?

The General Pretreatment Permit for SIU Discharges to POTWs regulates the following discharges from certain facilities to a POTW:

• Metal finishing wastewater.
• Process and non-process wastewater that is not subject to categorical pretreatment standards.
• Dewatering wastewater.
• Remediation wastewater.
• Temporary and short-term discharges.
• Emergency discharges lasting less than 30 days.

Typical examples of facilities that are covered under the SIU GP include metal finishers, electroplaters, and chemical or food manufacturers. The reissuance of this permit continues Connecticut’s implementation of the federal pretreatment standards, ensuring pollutants are reduced or eliminated before being discharged from the facility.

What changes does the update include?

While the scope and applicability of the SIU permit remain the same, DEEP has renamed the permit to better reflect its regulatory role. Facilities currently registered under the SIU GP will transition to coverage under the updated Pretreatment General Permit now that it has officially been reissued (as of 10/29/25).

Other changes include updated pollutant monitoring, sampling, and reporting requirements, as well as revised electronic submission procedures.

Next steps for you

Existing SIU permittees should review the new CT DEEP General Pretreatment Permit for SIU Discharges to confirm if any changes apply to their facility. This may include new monitoring frequencies, analytical parameters, or updated pretreatment and maintenance standards.

If your facility has been covered under the previous SIU GP, you must submit your application for the new version of the permit by 3/1/26. DEEP will begin accepting applications on 12/1/25.

The current version of this general permit expires on 10/28/30.

How Walden can help

If your facility discharges process wastewater to a POTW or needs help determining if you qualify as an SIU, Walden’s EHS specialists can help you maintain compliance and prepare your registration package. Contact us today at 860-846-4069 to learn more.