A stormwater management system is made up of capture, conveyance, pretreatment, treatment, storage or infiltration, and discharge — and choosing where filtration media belongs depends on the pollutants, the site constraints, and the permit driving the work.
A stormwater management system is the full chain that moves runoff from the point it hits pavement to the point it leaves a site, and it is usually built from six working parts: capture, conveyance, pretreatment, treatment, storage or infiltration, and discharge. Knowing what each stage does is the first step toward deciding where a filtration product belongs, because a catch basin insert and a polishing vessel solve different problems even though both sit inside the same system.
What does each stage of a stormwater system actually do?
Capture is the inlet point — a catch basin, deck drain, or grate — where runoff first enters the built system. Conveyance is the piping, channel, or swale that carries water from capture toward the next stage; its job is movement, not treatment. Pretreatment removes the coarse load before it reaches anything finer downstream: trash, debris, floating sheen, and settleable sediment. Treatment is where the dissolved and fine-particulate fraction gets addressed — the metals, hydrocarbons, bacteria, nutrients, and compounds like PFAS that pretreatment does not touch. Storage or infiltration holds or releases water at a controlled rate, whether that's a detention vault, an infiltration basin, or a pressure vessel. Discharge is the outfall or connection point where the permit limits actually get measured.
Sediment control alone tends to concentrate on capture, conveyance, and pretreatment. That leaves a gap at the treatment stage for anything that has dissolved into the water column rather than settled out — which is where a permit holder often runs into trouble on benchmark monitoring even after installing a system that looks complete on paper.
How do you decide which stage needs a treatment product?
Start with what the water is carrying
The pollutant mix on site determines which media belongs at which stage. A metal recycling yard, fabrication shop, or junkyard typically has dissolved iron, copper, zinc, lead or arsenic in runoff, along with phosphorus from certain process residues — contaminants that Smart Sponge® HM is formulated to target. A municipal wastewater operator working toward a phosphorus discharge or reuse limit faces the same chemistry from a different source. Fuel docks, bilge areas, and equipment washdowns at marinas and boatyards put hydrocarbons and oil sheen into the water instead, which is what standard Smart Sponge® media is built to bind. Sites with bacteria concerns tied to a TMDL — beaches, shellfish waters, recreational contact zones — need an antimicrobial approach, and Smart Sponge® Plus is formulated for E. coli, fecal coliform and enterococcus. Where total organic carbon or dissolved organic compounds are the driver, Smart Sponge® AC is the relevant media, and where PFAS is on the sampling plan, Smart Sponge® Quanta™ is built for that fraction specifically. Because several of these media can be combined within one system, a site carrying more than one pollutant class doesn't necessarily need more than one treatment stage — it needs the right combination at that stage.
Match the format to the space you actually have
Once the pollutant is identified, the question becomes where the media can physically sit. Existing catch basins and deck drains can take a custom-fabricated catch basin insert filter like the Ultra Urban® Filter, built to the basin's own geometry rather than forcing a standard size into a non-standard opening — useful for retrofits where excavation isn't an option, and equally viable specified into new construction. Larger paved catchments or sites with existing vaults, tanks or pressure vessels can take bulk filtration media loaded directly into that infrastructure, avoiding a rebuild. Where a site needs engineered flow or pressure control rather than passive gravity flow, Abtech's skid-mounted Smart Skid systems run with pumps and flow controls rather than operating power-free. Outfalls, channels, and discharge points can take Smart Pak®, Smart Bags, or EOP units, while floating fuel sheen at fueling docks or slips is better addressed with skimmers, booms, or Smart Drum units than with an inline insert. The format decision is really a space-and-infrastructure decision: what's already there, what can be opened up, and what has to stay passive versus what can justify powered controls.
Frequently Asked Questions
Does pretreatment remove the same pollutants as treatment media?
No. Pretreatment is built for trash, debris, and settleable sediment — the particulate fraction. Treatment media addresses what pretreatment leaves behind: dissolved metals, hydrocarbons, bacteria, nutrients like phosphorus, and compounds such as PFAS. A system with only pretreatment can still fail a dissolved-pollutant benchmark.
Can one catch basin insert handle more than one pollutant?
It can, depending on which media is loaded into it. Because several Smart Sponge® formulations can be combined within a single insert or vessel, a basin facing both hydrocarbons and dissolved metals, for instance, doesn't automatically need two separate systems.
Is a catch basin insert always the right format?
Not always. Inserts suit existing basins and deck drains where excavation isn't practical. Larger catchments, or sites with existing vaults, tanks or pressure vessels, are often better served by bulk media loaded into that infrastructure, and sites needing engineered flow control may need a skid-mounted system with pumps rather than a passive insert.
What should drive the choice between media types?
The pollutant mix the site actually produces, confirmed against sampling data where it exists. A metal recycling yard's dissolved-metals and phosphorus profile calls for a different media than a marina's fuel sheen or a wastewater plant's bacteria limit, and guessing at the mix instead of checking it tends to produce a mismatched system.
How do regulatory changes affect an already-installed system?
A rule change can redefine what counts as adequate even if the hardware hasn't changed. Updated inspection, reporting, or trash-capture standards can mean a system built to an older standard needs a documented upgrade at the treatment or pretreatment stage, not just routine servicing.