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Effluent Guidelines

Grain Mills Effluent Guidelines

""EPA initially promulgated the Grain Mills Effluent Guidelines and Standards (40 CFR Part 406) in 1974 and 1975 and amended the regulation between 1975 and 1986. The regulation covers directHelpdirect dischargerA point source that discharges pollutants to waters of the United States, such as streams, lakes, or oceans. and indirectHelpindirect dischargerA facility that discharges pollutants to a publicly owned treatment works (municipal sewage treatment plant). dischargers. The Effluent Guidelines and Standards are incorporated into NPDES permits for direct dischargers and permits or other control mechanisms for indirect dischargers (see Pretreatment Program).

On this page:

What is the Grain Mills Industry?

The industry comprises grain operations in several product segments:

  1. Cereal grains. Corn, wheat, and rice milling and processing are covered in the Part 406 regulation.
  2. Animal feed
  3. Breakfast cereal manufacturing
  4. Wheat starch and gluten manufacturing
Grain mills are included within the following North American Industry Classification System (NAICS) groups:
  • 311119: Other Animal Food Manufacturing
  • 311211: Flour Milling
  • 311212: Rice Milling
  • 311221: Wet Corn Milling
  • 311230: Breakfast Cereal Manufacturing
The NAICS listing is provided as a guide and does not define the coverage of the Grain Mills category. For precise definitions of coverage, see the applicability sections in 40 CFR Part 406.

Wastestreams, Pollutants and Subcategories


The industry's principal wastestreams are:

  • In multiple subcategories:
    • grain cleaning
    • cooking
  • In corn wet milling plants:
    •  modified starch washing
    •  condensation from steepwater evaporation
    •  syrup refining

Regulated Pollutants

Effluent limitations vary by subcategory. Some subcategories have zero discharge requirements.
  • BOD5
  • TSS
  • pH

Regulation Subcategories

  1. Corn Wet Milling
  2. Corn Dry Milling
  3. Normal Wheat Flour Milling
  4. Bulgur Wheat Flour Milling
  5. Normal Rice Milling
  1. Parboiled Rice Processing
  2. Animal Feed
  3. Hot Cereal
  4. Ready-to-Eat Cereal
  5. Wheat Starch and Gluten

Rulemaking History


In addition to the BCT amendments, portions of Part 406 were revised between 1975 and 1977 pursuant to litigation. For the current regulatory requirements see 40 CFR Part 406.

Initial Rulemaking

1975 rule ("Phase II")

Subparts G-J; BPT, BAT, NSPS, PSNS
    • Final Rule (January 3, 1975)
    • Development Document (December 1974)
    • Proposed Rule (September 17, 1974)

1974 rule ("Phase I")

Subparts A-F; BPT, BAT, NSPS, PSNS
    • Final Rule (March 20, 1974)
    • Development Document (March 1974)
    • Proposed Rule (December 4, 1973)

Additional Information

For additional information regarding Grain Mills Effluent Guidelines, please contact Meghan Hessenauer ( or 202-566-1040.

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