Treatment Agreements

Significant Industrial Users (SIUs)

A treatment agreement (TA) is needed if a Significant Industrial User (SIU) discharges to a publicly owned treatment works (POTW). An SIU is an industrial user of a POTW that meets any one of the following conditions:

1. Discharges an average of 25,000 gallons per day or more of process wastewater excluding sanitary, noncontact cooling and boiler blowdown wastewater;
2. Contributes a process waste stream which makes up 5 percent or more of the average dry weather hydraulic or organic capacity of the POTW;
3. Is subject to Categorical Pretreatment Standards under 40 CFR 403.6 and 40 CFR Chapter I, Subchapter N; or
4. Is designated by the DNR as an SIU on the basis that the contributing industry, either singly or in combination with other contributing industries, has a reasonable potential to adversely affect the operation of or effluent quality from the POTW or for violating any pretreatment standards or requirements.

Upon a finding that an industrial user meeting the criteria in paragraph 1 or 2 has no reasonable potential for adversely affecting operation of the POTW or for violating any pretreatment standard or requirement, the DNR may, on its own initiative or in response to a request from an industrial user or POTW, determine that an industrial user is not a significant industrial user.

Treatment Agreement Submittal Requirements

SIUs must submit a Treatment Agreement (TA) to DNR which:

• Is on on the treatment agreement form (542-3221) ;
• Identifies and limits the monthly average and daily maximum quantity of compatible and incompatible pollutants discharged to the POTW,
• Identifies variations in daily flow;
• Is signed and dated by the SIU and the owner of the disposal system accepting the wastewater; and
• Provides that the quantities discharged to the disposal system will comply with the applicable requirements in 567 IAC Chapter 62.

Industrial User Survey:

• Businesses who may be SIUs should complete and submit the Industrial User Survey (542-0833). Return the completed survey to npdes.mail@dnr.iowa.gov.
• Cities may provide the Industrial User Survey to local businesses at their discretion.

Federal Pretreatment Standards & Baseline Monitoring Reports:

• If an SIU is subject to Federal Pretreatment Standards, the limits in the TA must be at least as stringent as the applicable federal pretreatment standards.
• Categorical industries subject to federal pretreatment standards must submit a Baseline Monitoring Report (BMR) that includes discharge data.

Total Toxic Organics (TTO) Monitoring & TOMPs:

• SIUs that discharge Total Toxic Organics (TTOs) may prepare a toxic organic management plan (TOMP) as an alternative to routine TTO monitoring.
• The TOMP option is available to regulated industrial users in the Electroplating, Metal Finishing, and Electrical and Electronic Components categories.

Treatment Agreement Submittal Timelines

Timeline for New SIUs (newly constructed facility):

• For new SIUs, a TA form must be submitted to DNR at least 180 days before the SIU proposes to discharge to a POTW.
• The owner of a POTW shall submit a treatment agreement at least 10 days prior to making a commitment to accept waste from a proposed new SIU. However, DNR may notify a POTW that a TA review may take longer than 10 days and advise the POTW to wait on entering into a commitment until the review is complete.

Timeline for Existing SIUs (facilities that have a current TA or currently discharge to a POTW below the SIU threshold):

• An existing SIU must submit a new TA form to DNR 60 days in advance of a proposed expansion, production increase or process modification that results in discharges of waste in excess of the discharges stated in the existing TA.
• An industry that will become an SIU must submit a TA form to DNR 60 days in advance of a proposed expansion, production increase, or process modification that will result in the industry qualifying as an SIU.
• The owner of a POTW is required to submit all TA forms from existing SIUs when completing a permit application. See Form 30 - Part D of the Municipal/ Semi-public Permit application for more information.

Timeline for wastewater treatment plant construction or upgrade:

• A facility plan or preliminary engineering report for the construction or modification of a POTW must include a treatment agreement form for each significant industrial user of the POTW.

More Information

For more information on industrial discharges and Treatment Agreement, please see the Industrial Discharges and Treatment Agreements Presentation, 2/21/2023.