USEPA maintains a list of 51 types of industries, and sets guidelines for their discharges. These industries are classified as ___ industrial users.

• A. Primary
• B. General
• C. Categorical
• D. Minor

Answer: (C)

The list of 51 industry types is used to define what EPA calls categorical industrial users. These are the industries that have their own industry-specific discharge standards known as categorical pretreatment standards. Because a discharge from each of these categories is regulated by these detailed, category-based limits rather than general limits, they’re classified as categorical industrial users.

Other terms don’t fit because they aren’t the formal EPA classification for these industry-specific discharges; “general” would imply broader, non-category standards, and “minor” or “primary” aren’t the official designations used for this group.