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Treatment Agreements for Significant Industrial Users

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 department as a significant industrial user on the basis that the contributing industry, either singly or in combination with other contributing industries, has a reasonable potential for adversely affecting 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

Significant industrial users must submit a Treatment Agreement (TA) to DNR which:

    • Is on on the treatment agreement form #542-3221 or 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, form #542-0833 . Return the completed survey to the Iowa DNR.
    • Cities may provide the Industrial User Survey to local businesses at their discretion.
    Federal Pretreatment Standards and 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 and 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

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.

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.

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 and Contacts

For more information on industrial discharges and Treatment Agreement, please see the following presentation:

For Treatment Agreement questions, contact: