EPA Effluent Limitations Guidelines
What are EPA effluent limitations guidelines?
Effluent limitations guidelines (ELGs, usually just called "Effluent Guidelines") are, in EPA's words, "national wastewater discharge standards that are developed by the EPA on an industry-by-industry basis." They are technology-based rules covering industrial wastewater sent either directly to surface waters or to municipal sewage treatment plants (publicly owned treatment works, POTWs). EPA has issued them for 73 industrial categories, each with its own part of Title 40 of the CFR. (Learn about Effluent Guidelines; Industrial Effluent Guidelines)
What sets them apart
- Technology-based, not risk-based. The limits come from what treatment technology can achieve, aiming for "the greatest pollutant reductions that are economically achievable." They are not derived from risk assessments or receiving-water quality.
- Legal basis. They are issued under Title III of the Clean Water Act: section 304(b) for the technology-based limits, section 306 for new source performance standards, and section 307 for pretreatment standards.
- Set by industry. Each category, such as petroleum refining, pulp and paper or metal finishing, has its own CFR part. Within a part, the limits are split into subcategories.
The six levels of control
| Standard | Applies to | Basis |
|---|---|---|
| BPT | Existing direct dischargers | Best practicable control technology currently available |
| BAT | Existing direct dischargers | Best available technology economically achievable |
| BCT | Existing direct dischargers | Best conventional pollutant control technology |
| NSPS | New direct dischargers | Best available demonstrated control technology |
| PSES | Existing indirect dischargers (to POTWs) | Technology-based pretreatment standards |
| PSNS | New indirect dischargers (to POTWs) | Technology-based pretreatment standards |
Pollutants covered. The standards address three groups:
- Conventional pollutants: BOD5, TSS, fecal coliform, pH, and oil and grease.
- Toxic or "priority" pollutants.
- Nonconventional pollutants.
How they are applied in practice
- Direct dischargers: the guideline limits are written into the facility's NPDES permit as effluent limits.
- Indirect dischargers: the limits are enforced through the National Pretreatment Program (40 CFR Part 403) by the POTW or the pretreatment control authority.
Examples of categories and their 40 CFR parts: dairy products processing (405), textile mills (410), electroplating (413), petroleum refining (419), iron and steel (420), pulp, paper and paperboard (430), meat and poultry (432), metal finishing (433), coal mining (434) and battery manufacturing (461).
Approach: I tried EPA's Effluent Guidelines category register and the Clean Water Act text (33 U.S.C. chapter 26) in our datasets, but couldn't get results from either this time. The answer above comes from EPA's official Effluent Guidelines pages. I can list all 73 categories with their CFR parts, or pull the limits for a particular industry, when you need them.
How do I find the limits for my industry?
To find your limits, identify the point-source category in 40 CFR Subchapter N (Parts 405-471) that covers your processes. Then read that Part's applicability section to choose the subpart, and take the numbers from the section for your discharger type: BPT, BAT, BCT or NSPS if you discharge directly to a water body, or PSES/PSNS if you discharge to a municipal sewer (POTW). Metal finishing (40 CFR Part 433) is used below as a worked example.
Step 1: Find your category. EPA's Industrial Effluent Guidelines page has a table of every category in alphabetical order. Each row gives the 40 CFR Part, links straight to the regulation, and shows the year it was first issued and last revised. EPA's Effluent Guidelines Database (tool at owapps.epa.gov/elg/) lets you search "individual effluent limitations and definitions within the industrial category regulations" by industrial category, pollutant, treatment technology basis or keyword. That makes it useful if you know your pollutants but not your category.
Step 2: Confirm the category applies by reading its applicability section. Coverage depends on the processes you run, not your company's description of itself. Part 433 shows how this works (eCFR, 40 CFR Part 433):
- §433.10(a): the Part applies to plants that perform any of six core operations: electroplating, electroless plating, anodizing, coating, chemical etching and milling, or printed circuit board manufacture. Once one of those is present, it also covers discharges from 40 listed ancillary operations, such as cleaning, machining and painting.
- §433.10(b): where another category, such as iron and steel (Part 420) or battery manufacturing (Part 461), applies to those operations, "these part 433 limits shall not apply" and that other Part governs instead.
- §433.10(c): the Part does not apply to existing indirect-discharging job shops and independent printed circuit board manufacturers. Those fall under Part 413.
Check for overlaps like these in your own category. A multi-process site can fall under more than one Part.
Step 3: Pick the right subpart and section. Each Part follows the same layout: applicability, definitions, monitoring, then one section per standard. In Part 433:
| Section | Standard | Who it applies to |
|---|---|---|
| §433.13 | BPT | Existing direct dischargers |
| §433.14 | BAT | Existing direct dischargers |
| §433.15 | PSES | Existing sources discharging to a POTW |
| §433.16 | NSPS | New direct dischargers |
| §433.17 | PSNS | New sources discharging to a POTW |
Step 4: Read the tables and the conditions attached to them. The limits are usually given as "Maximum for any 1 day" and "Monthly average shall not exceed". For example:
- Cadmium (T): 0.69 / 0.26 mg/l under BPT (§433.13), but 0.11 / 0.07 mg/l under NSPS (§433.16).
- pH: the BPT table gives a range, "Within 6.0 to 9.0."
The conditions around the tables can matter as much as the numbers:
- Alternative cyanide limit: an amenable-cyanide limit "may apply" in place of the total-cyanide limit, but only "upon agreement" with the control authority.
- Dilution ban: "No user subject to the provisions of this subpart shall augment the use of process wastewater or otherwise dilute the wastewater" to achieve compliance.
- Certification instead of monitoring: the permitting or control authority "may allow" you to certify for total toxic organics (TTO) instead of monitoring for them. In return, you "shall submit a solvent management plan" (§433.12).
- Extra limit for existing indirect dischargers: they "shall comply with a daily maximum pretreatment standard for TTO of 4.57 mg/l" (§433.15(e)).
- Shared definitions and test methods: the definitions in Part 401 and the analytical methods in Part 136 are incorporated by reference (§433.11).
Step 5: Use the right version of the text. eCFR says its content is "authoritative but unofficial". The official edition is the annual CFR on govinfo.gov. eCFR's timeline is also worth a look: for Part 433 it shows no changes after 1/03/2017.
Approach: I first tried EPA's Effluent Guidelines category register in our datasets, but couldn't get results from it this time. So the steps above come from EPA's Effluent Guidelines pages and the eCFR text of 40 CFR Part 433.
If you tell me your industry or main processes, I can work out the category and subpart and pull the actual limit tables for you.