Pretreatment FAQs

All industrial users located within the District of Columbia must comply with DC Water's Wastewater Discharge Regulations. However, industrial users that perform processes deemed "categorical" by the EPA and/or significant or non-significant by DC Water, must comply with additional requirements.

The term Significant Industrial User (SIU) as defined by the EPA means:

All industrial users subject to Categorical Pretreatment Standards under 40 CFR 403.6 and 40 CFR chapter I, subchapter N; and

Any other industrial user that does the following:

  • discharges an average of 25,000 gallons per day or more of process wastewater;
  • contributes a process wastestream that makes up 5% or more of the average dry weather hydraulic or organic capacity of the treatment plant; or
  • is designated as a SIU by DC Water on the basis that the industrial user has a reasonable potential for adversely affecting the operation of DC Water's wastewater treatment plant.

Potential SIUs under construction should apply for a DC Water Industrial Wastewater Discharge Permit at least 90 days prior to discharging to the DC Water's sanitary sewer. Existing industrial users should apply as soon as possible.

Complete the appropriate permit application obtained from this website or contact the Pretreatment Program Manager at 202-787-4177. Sign the completed application and include all requested attachments and mail or hand deliver to the Pretreatment Program Manager in the Department of Wastewater Treatment at 5000 Overlook Ave., SW, in Washington, D.C. Applications may be emailed in advance to with hard copy to follow in the mail.

If an Industrial User does not comply with pretreatment program requirements, it will be subject to enforcement action by DC Water.

Pretreatment is the reduction, the elimination, or the alteration of pollutants in wastewater to a less harmful state prior to discharge of the wastewater to a sanitary sewer system.

It is an EPA-mandated program that requires DC Water to regulate industrial discharges to DC Water's wastewater collection system. This reduces the amount of pollutants released into the environment from our treatment plant.

DC Water operates the Blue Plains Advanced Wastewater Treatment facility and treats wastewater from domestic and industrial sources. After treatment, the cleaned water is returned into the environment. DC Water’s NPDES permit issued by the EPA regulates the quality of the water that is discharged into the District’s waterways. The permit contains requirements to maintain an approved pretreatment program to prevent pollution of the waterways.

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