Wastewater Testing vs Stormwater Testing: What Illinois Businesses Need to Know
Updated: Sep 18
Table of Contents:
Wastewater Testing vs Stormwater Testing:
Businesses across Illinois and the Chicagoland Area often struggle to understand the difference between wastewater testing and stormwater testing. Both testings are critical for environmental compliance; however, they each serve very different purposes, follow different regulations, and apply to different types of operations.
Our guide breaks down the differences clearly, using real regulatory requirements to help Illinois businesses understand what they need and why.
What Wastewater Testing Measures:
Wastewater testing focuses on water that has been used inside your facility from sinks to anything discharged to a municipal sewer system.
Common parameters include:
TSS (Total Suspended Solids)
BOD (Biochemical Oxygen Demand)
COD (Chemical Oxygen Demand)
PH, oil & grease, metals, nutrients
These tests help determine how strong or polluted your wastewater is before it reaches a treatment plant such as the MWRD or a local municipal system.
Who Needs Wastewater Testing?
Wastewater testing is required for:
Manufactures
Food processors
Auto shops and body shops
Metal finishers and plating shops
Industrial laundries
Any business with a pretreatment permit
If your facility discharges to a sewer, you likely fall under NPDES permit or local pretreatment rules.
Why It Matters?
High wastewater strength can damage sewer infrastructure, overload treatment plants, and violate discharge limits. Municipalities enforce strict requirements, especially in the Chicagoland Area, where searches for Chicago sewerage treatment plant have surged 900%.
Wastewater testing ensures your business:
Meets discharge limits
Avoids fines
Maintain permit compliance
Protects local water systems
What Stormwater Testing Measures:
Stormwater testing focuses on rainfall that contacts outdoor surfaces, parking lots, loading docks, scrap yards, chemical storage areas, or any industrial activity exposed to the weather.
Stormwater testing typically measures:
TSS
Oil & grease
Metals (zinc, copper, lead)
pH
Runoff pollutants from outdoor operations
Who Needs Stormwater Testing?
Stormwater testing applies to facilities covered under the Industrial Stormwater General Permit, including:
Auto recyclers
Transportation yards
Outdoor manufacturing
Warehouses with exposed materials
Scrap yards
Construction sites
If your business has outdoor industrial activity, you likely need stormwater sampling and a SWPPP (Stormwater Pollution Prevention Plan).
Stormwater runoff can carry pollutants directly into rivers, lakes, and drainage systems. Illinois businesses must comply with EPA stormwater rules, especially during heavy rainfall seasons.
Key Differences:
Category | Wastewater Testing | Stormwater Testing |
Source | Indoor drains, process water | Outdoor runoff from rain |
Regulatory | Municipalities, MWRD, IEPA | EPA, IEPA |
Common Tests | BOD, COD, TSS, pH, metals | TSS, metals, oil & grease |
When Required | Continuous or scheduled | During qualifying rain events |
Risk | Sewer damage, permit violations | Pollution entering waterways |
Compliance Deadlines & Sampling Frequency:
Illinois facilities must follow strict timelines:
Wastewater testing: Monthly, quarterly, or semi-annual depending on permit
Stormwater testing: 2-4 times per year during qualifying rain events
NPDES reporting: Annual or semi-annual
SWPPP updates: Annually or after major site changes
Missing a sampling deadline is one of the most common causes of violations.
How Eagle Handles Both:
Eagle provides full-service environmental compliance support for Illinois businesses, including:
Wastewater sampling & analysis
Stormwater sampling during rain events
NPDES permit guidance
SWPPP development
Reporting & documentation
On-site inspections
Compliance consulting for manufactures, auto shops, and food processors
Our team ensures your facility meets all IEPA, EPA, and municipal requirements, without the stress of navigating complex regulations alone.
Final Takeaway:
Wastewater testing and stormwater testing serve different purposes, protect different parts of the environment, and apply to different types of businesses. Understanding which one your facility needs is critical for staying complaint and avoiding costly violations.
If your business operates in Illinois or the Chicagoland Area, Eagle can help you determine exactly what testing applies to your operation, and handling the entire process from sampling to reporting.
Frequently Asked Questions:
What is the difference between wastewater and stormwater testing?
Who needs wastewater testing in Illinois?
Manufactures, food processors, auto shops, metal finishers
Any facility discharging to a municipal sewer
Business with pretreatment permits
Facilities exceeding TSS, BOD, COD limits
Operations monitored by MWRD or local municipalities
What pollutants are tested in wastewater?
TSS, BOD, COD (core strength parameters)
Oil & grease, nutrients, metals
pH and industrial process contaminants
Indicators of organic load and treatment impact
Used to determine compliance with local discharge limits
What pollutants are tested in stormwater?
TSS, oil & grease, metals (zinc, copper, lead)
Runoff pollutants from parking lots, docks, storage areas
pH and visible sheen
Indicators of outdoor contamination
Required during qualifying rain events
How often do business need to test wastewater?
Monthly, quarterly, or semi-annual depending on permit
Frequency set by municipal pretreatment programs
Higher-risk facilities may require more frequent sampling
Results must be submitted to the local authority
Missing deadlines can trigger violations or fines
How often do businesses need stormwater sampling?
Typically 2-4 times per year
Must occur during qualifying rain events
Required under NPDES Industrial Stormwater Permit
Results included in annual stormwater reports
Facilities must maintain an updated SWPPP
How can Eagle help with compliance?
Full wastewater & stormwater sampling services
NPDES permit guidance and reporting
SWPPP development and annual updates
On-site inspections and corrective action plans
Support for manufactures, auto shops, food processors, and more.
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