Arsenic removal from stormwater depends on whether the arsenic is dissolved or particulate. Here is how to tell, which media targets it, and how to choose a format.
Arsenic removal from stormwater starts with finding out whether the arsenic is dissolved or attached to particles, because sediment control only handles the particulate share. Smart Sponge® HM media targets dissolved arsenic along with lead, selenium, zinc and copper, and it can be deployed in catch basin inserts, vaults or vessels matched to the site.
Why Sediment Control Alone Rarely Settles an Arsenic Problem
Settling basins, screens and standard catch basin sumps capture solids. Whatever arsenic rides on those solids can drop out with them, but arsenic that is dissolved passes through to the outfall. For a facility under NPDES, MSGP and SWPPP requirements, that dissolved portion is usually the reason a benchmark exceedance returns after housekeeping and sediment controls are already in place.
Dissolved metals behave the same way across the group, which is why our page on what causes heavy metals in stormwater is a useful companion when you are tracing where metals enter a drainage system. Metal recycling yards, fabrication shops and sites with scrap storage are the settings where we most often see metals discussed in permit work.
Where Does Arsenic in Stormwater Come From?
Two routes deserve a look. The first is the site itself: metal-bearing materials stored or processed outdoors expose their surfaces to rain. The second is natural. The U.S. Geological Survey notes that, in its study of in-situ arsenic removal during groundwater recharge, arsenic is naturally present in aquifers throughout the southwestern United States and elsewhere. Where groundwater reaches a storm drain or a collection sump, a natural background can be part of what you measure, and no amount of site housekeeping will change it.
Separating those routes matters because it decides what a treatment system must handle. A discharge dominated by site activity may carry several metals at once. A discharge with a natural groundwater component may carry arsenic with little else.
Dissolved or Particulate: What Each Fraction Needs
| Fraction | What it means | What generally addresses it |
|---|---|---|
| Particulate arsenic | Bound to soil, dust or scale carried in runoff | Settling, screening and filtration of solids |
| Dissolved arsenic | Moves with the water through sumps and screens | Sorptive media that binds the metal as water passes through |
| Mixed | Both fractions in the same discharge | Solids capture upstream, dissolved-metals media downstream |
Lab results that report total and dissolved arsenic separately tell you which row you are in. If the dissolved fraction is small, better solids control may be enough. If it is large, the media decision comes next.
Which Smart Sponge® Media Targets Arsenic?
Smart Sponge® HM is the media aimed at dissolved metals, including arsenic, lead, selenium, zinc and copper, and also phosphorus. Standard Smart Sponge® is a different media: it is hydrophobic and oil-attracting, so it handles hydrocarbons rather than metals. When a site carries both, several media can be combined in one system. We state what the media targets or binds and do not promise removal rates, because performance depends on the water chemistry, contact conditions and the discharge limit at your outfall.
If zinc and copper drive your exceedances alongside arsenic, our guide to zinc and copper removal from industrial stormwater covers the same dissolved-metals logic in more depth.
Which Format Holds the Media?
The media follows the contaminant; the format follows the site. Once Smart Sponge® HM is the right media, the structures already on your property decide how it gets deployed.
- Ultra Urban® Filter catch basin inserts: custom-fabricated to each basin's geometry, they retrofit existing basins without excavation and run without pumps or power. Stainless steel inserts carry a 20-year warranty.
- Bulk Smart Sponge® media: loaded into existing pressure vessels, skids, tanks and vaults, which suits sites that already have a treatment structure.
- Smart Skid systems and Abtech vessels: used where a packaged unit makes sense. These are installed with pumps, pressure and flow controls, so they are not power-free.
- Smart Pak®, Smart Bags and EOP units: for vaults, channels, outfalls and discharge points.
For vessel and vault applications, see our overview of bulk filtration media for stormwater vaults and pressure vessels. For drain-level retrofits, our explanation of the catch basin insert filter for stormwater shows how the insert and media work together.
What Drinking-Water Arsenic Research Does and Does Not Tell You
Most published arsenic treatment work addresses drinking water. The U.S. EPA's arsenic treatment technology demonstrations followed the agency's move to lower the drinking water standard from 50 to 10 micrograms per liter, and they evaluated reliability, operator skill, cost and treatment residuals. Those are the right questions to carry over to a stormwater project: how reliable is the system, who maintains it, and what happens to the spent media.
FAQ
Can a catch basin insert treat dissolved arsenic?
An Ultra Urban® Filter insert is the format, and the media inside determines what it treats. Loaded with Smart Sponge® HM, an insert targets dissolved metals including arsenic. Whether an insert is enough depends on the contact time and loading at that basin, which the site assessment reviews.
Does Smart Sponge® HM also address phosphorus?
Yes, it targets phosphorus as well as dissolved metals. Because dissolved phosphorus is a separate permit concern, our sources of phosphorus in stormwater post explains where it originates on industrial sites.
Can several media be combined in one system?
Yes. Sites that carry hydrocarbons and dissolved metals together can combine media types in a single system, so one deployment addresses more than one contaminant class.
Is stormwater arsenic held to the drinking water standard?
Not by default. The drinking water standard applies to public water systems. Your stormwater obligation comes from the permit that governs your discharge, so start with its benchmark or limit and the basis for it. Treatment media then needs to be matched to the dissolved arsenic you actually measure at the outfall.
Related resources
- What Causes Heavy Metals in Stormwater? Zinc, Copper, Lead and Arsenic Sources by Site Type
- Zinc and Copper Removal from Industrial Stormwater: What Works
- Bulk Filtration Media for Stormwater Vaults, Pressure Vessels and Skids
- Catch Basin Insert Filter for Stormwater: How Ultra Urban® Filter and Smart Sponge® Media Work Together
- Sources of Phosphorus in Stormwater on Industrial Sites
- Bacteria Removal Stormwater E. coli: A Permit Holder's Guide — Abtech Industries