Which regulations apply to all industrial dischargers to POTWs?

Categorical regulations apply to all industrial dischargers to Publicly Owned Treatment Works (POTWs) because they are specifically established under the Clean Water Act to address discharges from particular industrial categories. These regulations are designed to limit pollutant discharges from various types of industries that may have a significant impact on water quality. Each category has distinct standards and requirements that are intended to protect both the treatment facilities and the receiving waters.

Universal regulations typically refer to broader rules that apply across the board to various dischargers but do not target specific industries with the focused and stringent standards that categorical regulations do. State regulations may vary widely depending on local laws and conditions, and local ordinances are even more specific and localized. Hence, while these options may govern discharges in some capacity, they do not encapsulate the targeted and comprehensive nature of categorical regulations that directly addresses the unique challenges posed by industrial discharges.