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The term pretreatment means the reduction, elimination, or alteration of the nature of pollutant properties in wastewater prior to, or in lieu of, introducing them into a publicly owned treatment works (POTW). The EPA mandated the requirement to develop and operate an industrial pretreatment program effective on March 30, 1981.

The General Pretreatment Regulations are set forth in the Code of Federal Regulations, 40 CFR 403. Under the regulations, the District and any POTW with a design flow greater than 5 million gallons per day (mgd) must establish a pretreatment program as a condition of its National Pollutant Discharge Elimination System (NPDES) permit. The District obtained approval from the State Division of Water Quality to administer its pretreatment program with authority to permit, monitor, and enforce the requirements of the program by imposing fines for non-compliance. SIU (Significant Industrial Users) is a term assigned by the EPA to industries meeting specified criteria based on their potential to impact, interfere, or upset the ability of a treatment plant to treat the wastewater stream and meet its discharge standards. The District estimates about 10% of the total plant flow comes from SIUs.

Routine tasks associated with the District’s pretreatment program:

Annually the State conducts an inspection and audit of the District’s pretreatment program to verify compliance with applicable regulations.

All SIU’s are required by the District to be permitted. In an industry’s permit, discharge limitations are specified by federal categorical standards or locally developed and imposed standards. To determine compliance with their permitted limitations all SIUs choose to monitor themselves or have the District. If an industry elects to perform its own monitoring, the District complete at least one quarter of the monitoring to verify accuracy. The monitoring performed consists of taking samples over a 24-hour period using battery operated automatic samplers. It is important to preserve and maintain the most accurate sample possible by using proper techniques and verifying security against tampering. Samples are completed from a specific and special sampling manhole provided by each industry for pretreatment monitoring.

Summary of Pollutant Local Limits Per Industry


Monthly avg
Limit, mg/L

Limit, mg/L
Non-polar O&G
**Limits apply to all industrial users, users that meet criteria for Categorical Industrial users may be subject to Federal EPA standards as well.

After samples have been taken, they are delivered to the District’s laboratory or a third-party certified laboratory of the industry’s choosing. The laboratory runs analyses and creates a report on the samples to determine the concentrations of specified pollutants provided to the District’s Pretreatment Coordinator. After reviewing for compliance the coordinator enters the data into a special pretreatment computer program. The computer program helps determine compliance and maintains all pertinent records and data on all monitored industries.

Upon discovery of a violation of discharge limits, the pretreatment coordinator notifies the offending industry by phone and/or formal letter. In the case that the industry does not restore compliance within a given period the District has legal authority to impose compliance action requirements and, if warranted, monetary fines. If needed more severe action can be taken in the event that an industry refuses compliance including hearings before the Board of Trustees, criminal charges, and severing an industry’s connection to the sewer.

Laboratory analysis also partly determines the appropriate charges to be assessed to each industry. Industrial users are billed separately according to their actual wastewater volume and strength. Periodic or random inspections are conducted by the Pretreatment Coordinator and/or Pretreatment Manager designed to go beyond discharge limitations and determine compliance to other pretreatment requirements including proper record keeping, and proper storage and spill control of chemicals.

Certain industries are unable to meet their  permitted discharge limitations without performing treatment at their place of business to bring pollutant concentrations down to acceptable and specified levels before releasing them to the District’s system. There are only a few industries within the District that have pretreatment operations. Some operate highly technical pretreatment plants to treat a variety of waste streams including metal plating, cleaning solvents, and other toxic chemicals.

The goals of pretreatment:

The District’s program has successfully at reduced and controlled industrial discharges since the EPA mandated regulations were established.

Note to contractors and business owners

Please visit the NDSD contractors standard page, or contact Jonas Reeder the district's pretreatment coordinator at 801-728-6814 for drawings of a standard sampling manhole, and a typical grease interceptor (grease trap). For details on all other manhole specifications, please click here, or contact collections inspector Steve Lamb at 801-825-0712.

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