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Industrial Wastewater

image of factory and waterIndustry in Connecticut provides manufactured products and services sold in Connecticut and throughout the world. Wastewater generated from industrial activities can contain pollutants such as BOD (biochemical oxygen demand), suspended solids, nutrients, heavy metals, oils and greases, and other toxic organic and inorganic chemicals. If left untreated, these pollutants can cause serious harm to the environment.

The Department of Energy and Environmental Protection (DEEP) regulates the discharge of industrial wastewater to the ground water, surface water, and to sewage treatment plants through permitting programs. Discharge limits and requirements for treatment, monitoring and reporting, designed to protect the waters of the state from pollution, are specified in all permits.

Two types of permits are available for industrial wastewater discharges:

  1. Individual permits are issued directly to an applicant and are customized for a company's activities based on flow and the pollutants contained in the discharge.
  2. General permits cover a specific category of discharge and are issued to authorize similar minor activities by one or more applicants.

(DEEP Permits and Licenses page for Wastewater Discharges)

Learn more about:

Reissuance with Modifications of the General Permit for Discharges from Miscellaneous Industrial Users (MIU GP)

Issuance - General Permit for the Discharge of Wastewaters from Significant Industrial Users (SIU GP)

Issuance - General Permit for the Discharge of Groundwater Remediation Wastewater

Issuance - Comprehensive General Permit for Discharges to Surface Water and Groundwater

How to Comply with Your Permit

Related Information

Reissuance with Modifications of the General Permit for Discharges from Miscellaneous Industrial Users (MIU GP)

The General Permit for Discharges from Miscellaneous Industrial Users (MIU GP, issued September 29, 2020, effective October 31, 2020, formerly the General Permit for Miscellaneous Discharges of Sewer Compatible (MISC) Wastewater) continues to authorize discharges of “Miscellaneous Industrial User wastewater” (formerly “miscellaneous sewer compatible wastewater") either discharged directly to a Publicly Owned Treatment Works (POTW) or transported there by vehicle. However, the Industrial User initiating, creating, originating, or maintaining the discharge cannot be a Significant Industrial User (as defined in the general permit and summarized below).

A facility can be a Significant Industrial User if their non-domestic discharge:

  1. is subject to Categorical Pretreatment Standards under 40 CFR 403.6 and 40 CFR chapter I, subchapter N, or,
  2. has a cumulative maximum of 25,000 gallons per day or more of process wastewater to the POTW (excluding sanitary, noncontact cooling, and boiler blowdown wastewater) or,
  3. contributes a process wastestream which makes up 5 percent or more of the average dry weather hydraulic or organic capacity of the POTW Treatment plant; or,
  4. is designated as such by the Commissioner on the basis that the Industrial User has a reasonable potential for adversely affecting the POTW’s operation or for violating any Pretreatment Standard or requirement (in accordance with 40 CFR 403.8(f)(6)).

Permittees under the MIU GP will no longer submit registrations to DEEP, but will submit notifications to the “applicable POTW authority,” (most commonly the receiving POTW). The MIU GP Notification Form, Attachments, and Instructions are available on the DEEP Permits and Licenses webpage.

Issuance of the General Permit for the Discharge of Wastewaters from Significant Industrial Users (SIU GP)

The Significant Industrial User GP (SIU GP) authorizes discharges from Significant Industrial Users (as defined in the general permit) of metal finishing wastewater, process wastewater, or non-process wastewater to a Publicly Owned Treatment Works (POTW) either via the sanitary sewer or a properly licensed transporter. The SIU GP, Registration Form, and Instructions are available on the DEEP Permits and Licenses webpage.

Prior registrants under either the General Permit for the Discharge of Wastewaters from Categorical Industrial Users to a Publicly Owned Treatment Works (Categorical GP) or the General Permit for Miscellaneous Discharges of Sewer Compatible Wastewater (Miscellaneous or MISC GP) whose registrations expired October 30, 2020 and who are classified as Significant Industrial Users are authorized to discharge under the SIU GP provided:

  1. the registrant files a timely and sufficient registration under the SIU GP by January 29, 2021, and
  2. the registrant complies with the terms and conditions of the SIU GP until the Commissioner makes a final determination regarding such registration. 
Issuance of the General Permit for the Discharge of Groundwater Remediation Wastewater (Groundwater Remediation GP)

The Groundwater Remediation GP authorizes discharges of wastewaters generated during the process of investigating and remediating groundwater and soil, and other related wastewaters whether discharged to a surface water, groundwater, the collection system of a Publicly Owned Treatment Works (POTW) or hauled to a POTW.

This Groundwater Remediation GP combines and replaces the two recently expired groundwater remediation general permits that authorized discharges to sanitary sewer and surface water.  Many of the operational requirements remain substantively similar to the existing structure.  There are some significant changes to activities authorized, as well as new conditions applicable to surface water discharges.  The following summarizes the major changes:

  1. All discharges will be evaluated for emerging pollutants as defined by USEPA.  Should emerging pollutants be documented as a concern, conditions will be established as part of an approval of registration.
  2. Certification by a Qualified Professional, as defined in the permit, will be required for all discharges that continue for longer than thirty (30) days.
  3. All discharges will be screened for Total Nitrogen and Total Phosphorus.
  4. All discharges lasting longer than 90 days are subject to NetDMR reporting requirements.
  5. Discharges to Impaired Waters will be subject to specific conditions.
  6. The following discharges to surface water, which were previously ineligible for coverage, may now be covered under this general permit by issuance of an Approval of Registration:
    1. The discharge is directed to a receiving water with a water quality classification of AA or is tributary to a drinking water supply, or
    2. The combined discharge flow exceeds 10% of the 7Q10 flow of the receiving stream or ½% of the impoundment, lake or pond receiving the discharge, or
    3. The discharge uses a stormwater conveyance as part of the treatment system for the reduction of volatile organic compounds.
    4. Discharges may also be authorized to groundwater from specific remediation activities and from maintenance of remediation systems.

Renewal registrations are necessary under the current Groundwater Remediation GP.  The registration form and instructions are available on the DEEP Permits and Licenses webpage.

Issuance of the Comprehensive General Permit for Discharges to Surface Water and Groundwater (Comprehensive GP)

The Comprehensive GP replaces the surface and groundwater discharge portions of the following three general permits that expired March 29, 2018:

General Permit for the Discharge of Water Treatment Wastewater
General Permit for the Discharge of Non-contact Cooling Water and Heat Pump Water
General Permit for the Discharge of Hydrostatic Pressure Testing Wastewater. 

The Comprehensive GP also provides authorization for surface water and groundwater discharges of fire suppression testing wastewater, hydrant flushing wastewater, and boiler blowdown wastewater (to groundwater only when no boiler treatment chemicals are used).

The Comprehensive GP was issued December 14, 2017 with an effective date of March 30, 2018. Registrations for authorization under the Comprehensive GP for existing discharges must be submitted by June 28, 2018.

The registration form and instructions for the Comprehensive GP are available on the DEEP Permits and Licenses webpage.

A draft of the Comprehensive GP was publicly noticed September 30, 2016. Below please find:

Learn more about how to comply with your permit
Related Information

List of DPH Approved In-state Commercial Environmental Laboratories

Prohibition on Acceptance and Treatment of Wastes From Hydraulic Fracturing

Facility and Wastewater Treatment System Modifications Factsheet (in conjunction with
RCSA 22a-430-3(i))

NetDMR Electronic Discharge Monitoring Reporting

Fats, Oils, and Grease (FOG) Model Program

List of Connecticut Permitted Waste Transporters

List of Connecticut Publicly Owned Treatment Works (POTWs) Approved to Accept Transported, Non-domestic Wastewaters

Content Last Updated October 2020