Industrial stormwater vs. wastewater discharge permits
The Environmental Protection Agency (EPA) controls the amount of pollutants that reach the waters of the United States through the National Pollutant Discharge Elimination System (NPDES) permit program. The NPDES program covers two types of discharges from industrial sources:
- Stormwater discharges, and
- Wastewater discharges.
Although they’re under the same federal permitting program, stormwater and wastewater discharges are distinct, and their permits are too. Know the basic differences between these types of industrial discharges to ensure your facility complies.
Stormwater discharges
Rain and snow that flow over land or impervious surfaces (like building rooftops and parking lots) and don’t soak into the ground generate stormwater runoff. The runoff can gather pollutants generated by industrial activities at a facility and transport them into nearby waterbodies. Your facility must have a permit to discharge stormwater associated with industrial activities to waters of the United States (40 CFR 122.26).
The NPDES program regulates stormwater discharges from 11 categories of industrial activities, listed at 122.26(b)(14). Examples of covered activities include:
- Heavy manufacturing at chemical plants;
- Treating, storing, and disposing of hazardous waste; and
- Processing industrial wastes at landfills.
Note, however, that construction sites that disturb 5 or more acres (the tenth category) are permitted individually.
The permit contains stormwater control measures (including “best management practices”) to limit pollutants that enter stormwater runoff. Containment systems, employee training, and infiltration devices are all ways to control runoff.
Most states issue industrial stormwater discharge permits. EPA issues individual permits and the Multi-Sector General Permits (MSGPs) to facilities where the agency serves as the permitting authority. The MSGP is EPA’s general permit for industrial stormwater discharges.
Wastewater discharges
Many industrial processes use or generate water that contains pollutants, referred to as industrial wastewater. There are two types of wastewater:
- Process wastewater (defined at 122.2) refers to water used in manufacturing or processing activities.
- Non-process wastewater refers to water used for activities other than processing products (e.g., sanitary wastewater).
Your facility must have a permit to discharge industrial wastewater to surface waters (122.21(a)).
The NPDES program regulates direct wastewater discharges from industrial sources through rules based on the type of facility and activity. The regulations also have industry-specific requirements for:
- Animal Feeding Operations,
- Mining,
- Oil and Gas,
- Pesticide Applications, and
- Vessels Incidental Discharges.
Effluent limitations are the primary control method for industrial wastewater discharges. EPA establishes Effluent Limitations Guidelines (ELGs) for industrial categories and subcategories. These pollution-reduction performance standards are based on the best available technology that’s economically achievable by facilities in the industry. The ELGs are then incorporated into the permits through effluent limitations.
Additionally, industrial facilities must meet water quality-based effluent limitations when the technology-based standards don’t achieve the required standards for water quality. Both industrial stormwater and wastewater discharge permits may include technology- and water quality-based effluent limitations.
As with stormwater permits, most states issue industrial wastewater permits. Facilities in areas where EPA is the permitting authority must obtain either a general or individual NPDES permit.
Check your state requirements!
Because a majority of the states run stormwater and wastewater permitting programs, it’s crucial to check the state regulations. State permits must contain limits as stringent as EPA’s federal permits, and some states may impose stricter limits and/or additional requirements.
EPA’s website lists the states authorized to issue NPDES permits with links to the state agencies that run the NPDES program.
Key to remember: Industrial stormwater and wastewater discharges, and the permits that regulate them, are different.