---
kind: "unit"
title: "40"
title_heading: "Protection of Environment"
key: "chI/subchD/part133"
level: "part"
label: "Part 133"
heading: "Secondary Treatment Regulation"
release: "ecfr-current"
date: "2026-08-27"
url: "https://uscodex.org/cfr/40/chI-subchD-part133"
sections_count: 6
---

# Part 133 — Secondary Treatment Regulation

Title 40 C.F.R. — Protection of Environment › Chapter I — Environmental Protection Agency › Subchapter D — Water Programs

## Sections

- [§133.100. Purpose.](/cfr/40/133.100.md)
- [§133.101. Definitions.](/cfr/40/133.101.md)
- [§133.102. Secondary treatment.](/cfr/40/133.102.md)
- [§133.103. Special considerations.](/cfr/40/133.103.md)
- [§133.104. Sampling and test procedures.](/cfr/40/133.104.md)
- [§133.105. Treatment equivalent to secondary treatment.](/cfr/40/133.105.md)