Pretreatment standards are pollutant discharge limits which apply to industrial users (IUIUA source of indirect discharge. [40 CFR 403.3(j)]s). Pretreatment requirements are substantive or procedural requirements applied to IUs.

The national pretreatment program objectives are achieved by applying and enforcing three types of pretreatment standards:

• General and specific prohibitions
• Categorical pretreatment standards
• Local limits

All three types of standards can be enforced by EPA, the state, and local government, even though they are developed at different levels of government (i.e., federal, state, and local). Pretreatment standards and requirements can be expressed as numeric limits, narrative prohibitions, and best management practicesbest management practicesThe most effective and practical ways to control pollutants and meet environmental quality goals. BMPs exist for forestry, agriculture, stormwater and many other sectors. (BMPsBMPsThe most effective and practical ways to control pollutants and meet environmental quality goals. BMPs exist for forestry, agriculture, stormwater and many other sectors.).

IUs should be aware of the standards that apply to them. The control authoritycontrol authorityThe POTW, in the case of a POTW with an approved pretreatment program, or the Approval Authority, in the case of a POTW without an approved pretreatment program. [paraphrased from 40 CFR 403.3(f)] is responsible for identifying standard(s) applicable to each IU and applying the most stringent requirements where multiple provisions exist. The different pretreatment standards are applied to IUs, significant industrial users (SIUSIU(1) All users subject to categorical pretreatment standards under 40 CFR 403.6 and 40 CFR chapter I, subchapter N, except those designated as NSCIUs; and (2) Any other IU that discharges an average of 25,000 gallons per day or more of process wastewater to the POTW (excluding sanitary, noncontact cooling, and boiler blowdown wastewater); contributes a process wastestream that makes up 5 percent or more of the average dry-weather hydraulic or organic capacity of the POTW treatment plant; or is designated as such by the POTW on the basis that the IU 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)]. [40 CFR 403.3(v)]s), and categorical industrial users (CIUCIUAn industrial user subject to national categorical pretreatment standards.s) as follows:

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