Phosphorus removal from stormwater means treating both the particulate and dissolved fractions. See how Smart Sponge® HM targets dissolved phosphorus and metals, and where in the drainage chain to place it.
Phosphorus removal from stormwater requires treating two separate fractions — particulate phosphorus bound to sediment and dissolved orthophosphate suspended in the water column — because a catch basin sump or sediment trap only captures the first one. Smart Sponge® HM media is formulated to target dissolved phosphorus alongside dissolved metals, and it deploys inside catch basins, vaults, or pressure vessels so treatment sits where runoff already collects.
Why Does Sediment Control Leave Phosphorus Behind?
Total phosphorus in runoff splits into particulate phosphorus, which rides on suspended solids and settles out with TSS, and dissolved phosphorus, most of which shows up as orthophosphate — the form algae and aquatic plants take up most readily. A catch basin sump or a structural BMP built around settling will capture the particulate-bound share. The dissolved share stays in solution and passes through an untreated sump with the rest of the water column, which is why a site can sweep yards, maintain berms, and still see phosphorus benchmark exceedances at the outfall. The same particulate-versus-dissolved split shows up with heavy metals, and it means any corrective action plan has to name which fraction it is actually addressing.
Where Does Smart Sponge® HM Fit for Phosphorus and Dissolved Metals?
Smart Sponge® HM is the media in the Smart Sponge® filtration media family selected for dissolved-metal and phosphorus treatment, including lead, arsenic, selenium, zinc, and copper. Because it targets the dissolved fraction directly, it complements rather than duplicates the sediment capture that a standard sump or a sediment-focused Smart Sponge® media already provides. Sites where phosphorus and dissolved metals show up together — metal recycling yards, metal fabrication shops, and junk yard facilities under NPDES, MSGP, or SWPPP requirements — can address both within one media selection rather than running separate treatment trains for nutrients and metals.
Municipal wastewater operators working toward phosphorus limits on discharge or reuse water face the same dissolved-fraction problem, just further downstream than a catch basin. For that use case, wastewater polishing and reuse treatment can use bulk Smart Sponge® media loaded into existing pressure vessels, skids, tanks, or vaults, or a skid-mounted Smart Skid system — installed with pumps, pressure, and flow controls — where a facility needs a discrete polishing step ahead of a discharge limit.
Where in the Drainage Chain Should Treatment Sit?
Abtech's approach follows one principle across every project: the media follows the contaminant, and the format follows the site. For a paved catchment under an MS4 or NPDES permit, the practical entry point is often the catch basin itself. A catch basin retrofit fits media inside the sump volume that already exists, converting a collection point into a treatment point without excavation, pumps, or power. The Ultra Urban® Filter is custom-fabricated to the specific basin's shape and loaded with the appropriate Smart Sponge® media; stainless steel versions carry a 20-year warranty.
- Catch basin inserts (Ultra Urban® Filter) at the point where runoff first collects, sized to the basin without structural modification
- Smart Pak® and Smart Bags for vaults and hard-to-reach conveyance where a catch basin insert isn't the right fit
- EOP (end-of-pipe) units positioned at outfalls, as a last treatment step before discharge
- Vessels and Smart Skid pressure systems for municipal and industrial wastewater lines needing a polishing step ahead of a discharge or reuse limit
Treating closer to the outfall gives a permit holder a last chance to catch what upstream controls missed, but it also means treating a larger cumulative flow. Treating at the catch basin addresses phosphorus and dissolved metals nearer the source, before runoff mixes with the rest of the catchment. Neither placement is universally correct — the right answer depends on catchment size, available space, and where the permit's monitoring point sits, which is what a site assessment is meant to sort out before any format gets specified.
Does Treatment Need to Be Tested Before It's Installed?
For wastewater polishing and reuse applications, laboratory column testing on the customer's own water sample and pilot testing ahead of full-scale deployment are used because phosphorus concentration and water chemistry vary by site and affect which media configuration fits. A site assessment reviews contaminant concentrations, typical and peak flows, available space, effluent targets, and maintenance access before any system is specified, whether the application is a stormwater catch basin or a wastewater discharge line.
Frequently Asked Questions
Does a standard catch basin insert remove dissolved phosphorus, or just sediment?
A standard sump-style catch basin captures particulate-bound phosphorus riding on sediment but does not address dissolved orthophosphate, which stays in the water column and passes through untreated. Reaching the dissolved fraction requires media formulated for it, such as Smart Sponge® HM, placed inside the structure.
Can the same media address phosphorus and heavy metals together?
Smart Sponge® HM is selected for dissolved-metal and phosphorus treatment, so a site loading both — a metal recycling or fabrication yard with nutrient inputs, for example — can be addressed within one media selection rather than two separate treatment approaches.
Where should phosphorus treatment sit — at the catch basin or at the outfall?
Both locations are used depending on the site: catch basin inserts treat closer to the source before runoff mixes with the rest of the catchment, while EOP units at the outfall catch what upstream controls missed. A site assessment weighs catchment size, available space, and the permit's monitoring point to determine which placement fits.
Do I need to test my water before specifying phosphorus treatment media?
For wastewater polishing and reuse applications, column testing on the customer's own water sample and pilot testing are used before full-scale deployment, since phosphorus concentration and water chemistry vary by site and affect which media configuration is appropriate.
What other contaminants travel alongside phosphorus in stormwater?
Phosphorus often appears alongside dissolved metals, hydrocarbons, bacteria, and total organic carbon depending on site activity. Abtech's media family — including Smart Sponge® HM for metals and phosphorus, Smart Sponge® Plus for bacteria, and Smart Sponge® AC for organic compounds — can be combined within one system when a site's water carries more than one contaminant class. To match media and format to a specific site, schedule a site assessment.