Industrial BMP Deep Dive Series Part 4: Building a Stormwater Treatment Train
Why the right combination of BMPs matters more than relying on a single treatment solution.
Industrial stormwater rarely contains just one pollutant.
Depending on site operations, runoff can carry sediment, metals, oil and grease, hydrocarbons, and other pollutants — sometimes all within the same drainage area.
And because those pollutants behave differently in stormwater, a single BMP isn't always equipped to address the entire problem.
That's where a stormwater treatment train comes in.
What Is a Stormwater Treatment Train?
A stormwater treatment train is a series of Best Management Practices (BMPs) designed to work together, with each stage addressing a different part of the pollutant load.
Instead of asking one BMP to remove everything, a treatment train creates multiple opportunities to reduce pollutants before water reaches the discharge point.
A typical treatment strategy may include:
- Source control to reduce pollutant exposure
- Sediment and solids control to capture larger particles
- Pretreatment to reduce the pollutant load entering downstream systems
- Targeted treatment media for dissolved pollutants such as metals
- Oil and hydrocarbon treatment for petroleum-related contaminants
- Final filtration or polishing before discharge
Start With the Source
The most effective pollutant is the one that never reaches the stormwater system in the first place.
Before selecting treatment BMPs, facilities should identify where pollutants are coming from and how they are getting into runoff.
Common industrial pollutant sources can include:
- Outdoor material storage
- Vehicle and equipment traffic
- Loading and unloading areas
- Scrap or metal handling
- Equipment maintenance areas
- Exposed industrial materials
- Leaks and spills
- Accumulated sediment and debris
Source control measures such as improved housekeeping, covering exposed materials, correcting leaks, and reducing stormwater contact with industrial materials can reduce the pollutant load before treatment is even required.
Step 1: Slow the Flow and Capture Solids
Once pollutants are mobilized, stormwater can move quickly across an industrial site.
Flow management is therefore an important first layer of treatment.
Industrial wattles, sediment barriers, check structures, and other BMPs can help slow runoff and provide opportunities for suspended solids to settle or become captured.
This matters because sediment can create problems for downstream treatment systems.
When specialized treatment media receives excessive sediment loading, it can become clogged or blinded before it has an opportunity to effectively target dissolved pollutants.
Don't Make One BMP Do Every Job
One of the most common treatment challenges is expecting a specialized BMP to handle pollutants it wasn't designed to remove. Sediment controls, for example, can reduce particulate loading, while downstream treatment can focus on pollutants that remain dissolved in the water.
Step 2: Reduce the Pollutant Load
Pretreatment is an important part of an effective stormwater treatment strategy.
The goal is straightforward: remove as much of the easily captured material as possible before runoff reaches more specialized treatment.
For example, a facility dealing with metals may use sediment controls to capture suspended solids and particulate-bound metals first. Downstream treatment can then focus on dissolved metals that may pass through conventional sediment controls.
The same concept applies to hydrocarbons. Removing free-phase oil or larger contaminants upstream can reduce the amount of material reaching downstream carbon or other treatment media.
Step 3: Target the Pollutant
Once the larger and more easily captured pollutants have been addressed, treatment can become more specialized.
Different pollutants require different treatment mechanisms.
Metals
Dissolved metals can remain in stormwater even after suspended solids have been removed. Facilities may require specialized treatment media or other targeted technologies designed to address dissolved metals.
Oil & Grease
Free-phase oil can often be intercepted using appropriate absorbent or separation technologies before it moves farther through the drainage system.
Dissolved Hydrocarbons
When hydrocarbons are dissolved or otherwise difficult to physically separate, treatment may require adsorption-based media such as activated carbon or other specialized technologies.
Fine Suspended Solids
Where very fine particles remain suspended after initial treatment, additional filtration or polishing may be necessary depending on site conditions and discharge requirements.
The key is matching the treatment mechanism to the pollutant.
Step 4: Add a Final Polishing Layer
Even after multiple treatment stages, residual contaminants may remain in the water.
A final polishing stage can provide another opportunity to reduce remaining pollutants before discharge.
Depending on the site and treatment objectives, this may include:
- Carbon treatment
- Specialized filtration media
- Flow-through treatment systems
- Drain inserts
- Additional filtration
- Other site-specific treatment technologies
The goal isn't to make one BMP do everything. It's to make sure each stage is doing the job it was designed to do.
What Happens When You Skip a Layer?
A treatment train can become less effective when one BMP is expected to compensate for another.
| Approach | Potential Limitation |
|---|---|
| Sediment controls alone | Dissolved pollutants such as certain metals may remain in runoff. |
| Oil absorbents alone | They may not address dissolved hydrocarbons or other pollutants. |
| Specialized media without pretreatment | Excess sediment and solids can contribute to premature loading or clogging. |
| Treatment without flow control | Runoff may move through treatment too quickly for effective contact. |
| Good BMPs without maintenance | Performance can decline as BMPs accumulate sediment, become saturated, damaged, or bypassed. |
Design Around How Water Actually Moves
A treatment train should follow the site's actual drainage patterns — not simply where it is easiest to install a BMP.
That means understanding:
- Where runoff originates
- Where water concentrates
- Which areas contribute the highest pollutant loads
- Where pollutants enter the flow
- How quickly runoff moves
- Where treatment can realistically be installed
- Where maintenance and media replacement can be performed
A BMP installed in the wrong location can be ineffective even when the technology itself is appropriate.
Treatment needs to happen where the water is.
Maintenance Is Part of the Treatment Train
A treatment train isn't a set-it-and-forget-it system.
Every layer needs to remain functional throughout the monitoring season and during storm events.
Routine inspections should look for:
- Sediment accumulation
- Clogged or blinded media
- Damaged BMPs
- Displacement or bypass
- Saturated absorbent materials
- Reduced flow
- Changes in drainage patterns
Maintenance also provides an opportunity to identify problems before the next storm event.
A treatment system can only perform as well as the individual components that make it up.
The Goal Isn't More BMPs. It's Better BMPs.
Industrial stormwater management isn't about filling a site with as many BMPs as possible.
It's about understanding the pollutants, understanding the water, and putting the right controls in the right places.
A well-designed treatment train allows each BMP to focus on what it does best:
Control the source.
Reduce pollutant exposure before it reaches runoff.
Slow the flow.
Create opportunities to capture solids and reduce pollutant loading.
Target the dissolved pollutants.
Use specialized treatment where conventional BMPs may not be enough.
Polish the remaining contaminants.
Provide another layer of treatment before discharge.
Building a Treatment Strategy That Works in the Field
Every industrial site is different.
The right treatment train depends on the facility's operations, pollutant sources, drainage configuration, flow rates, existing BMPs, and monitoring results.
At Frog Environmental, we help industrial facilities evaluate their existing stormwater controls, identify treatment gaps, and develop practical BMP strategies based on how water and pollutants actually move across the site.
Because effective stormwater treatment isn't about finding one perfect BMP.
It's about building a system where every BMP has a job.
Frequently Asked Questions
What is a stormwater treatment train?
A treatment train is a series of stormwater BMPs that work together to address different pollutants or stages of treatment. Each BMP is selected based on the role it can effectively perform within the overall system.
Why isn't one BMP enough?
Industrial stormwater can contain multiple pollutants with very different physical and chemical characteristics. A BMP that effectively captures sediment, for example, may not address dissolved metals or hydrocarbons.
Should sediment be removed before specialized treatment?
In many treatment systems, pretreatment can help reduce the solids and sediment load reaching downstream treatment media. This can help specialized treatment focus on the pollutants it is designed to address.
How do I know which BMPs my facility needs?
BMP selection should be based on site-specific factors including industrial activities, pollutant sources, drainage patterns, flow conditions, existing controls, and monitoring results.
Can existing BMPs be incorporated into a treatment train?
Yes. Existing BMPs can often become one component of a broader treatment strategy. Evaluating how each BMP performs and where gaps remain is an important part of designing an effective treatment train.
Need a Second Look at Your BMP Strategy?
Our stormwater professionals can help evaluate your existing BMPs, identify treatment gaps, and develop a practical treatment strategy designed around your facility's specific conditions.
Schedule a Stormwater Consultation