The national pretreatment program is a component of the NPDES program. It is a cooperative effort of federal, state, and local environmental regulatory agencies established to protect water quality. Similar to how EPA authorizes the NPDES permit program to state, tribal, and territorial governments to perform permitting, administrative, and enforcement tasks for discharges to surface waters (NPDES program), EPA and authorized NPDES state pretreatment programs approve local municipalities to perform permitting, administrative, and enforcement tasks for discharges into the municipalities’ publicly owned treatment workspublicly owned treatment worksA treatment works (as defined by CWA section 212) that is owned by a state or municipality [as defined by CWA section 502(4)]. This definition includes any devices or systems used in the storage, treatment, recycling, and reclamation of municipal sewage or industrial wastes of a liquid nature. It also includes sewers, pipes, or other conveyances only if they convey wastewater to a POTW treatment plant. The term also means the municipality [as defined in CWA section 502(4)] that has jurisdiction over the indirect discharges to and the discharges from such a treatment works. [40 CFR 403.3(q)] (POTWs). 

• protect POTWspublicly owned treatment worksA municipal or public service district sewage treatment system. infrastructure, and
• reduce conventional and toxic pollutant levels discharged by industries and other nondomestic wastewater sources into municipal sewer systems and into the environment.

Introduction to the National Pretreatment Program - Summary of the national pretreatment program.