Catch Basin Inserts and Curb Inlet Filters for Heavy Metals

How a catch basin insert for heavy metals works, why dissolved zinc and copper need metal-binding media, and how to match an insert to a curb inlet.

A catch basin insert for heavy metals passes runoff through metal-binding media, such as Smart Sponge® HM, held in a frame built to fit your inlet. A curb inlet filter for heavy metals only works when the media targets the dissolved fraction and the format matches the opening. Here is how to judge both.

What Does a Heavy Metals Insert Actually Treat?

Metals travel in two forms. Particulate metals ride on sediment, and a screen or settling basket can catch some of them. Dissolved metals, such as zinc and copper, pass straight through a sediment-only insert because they are carried in the water itself. Permit benchmarks under NPDES, MSGP and MS4 programs often cover total metals, so a site can keep exceeding a benchmark even after housekeeping and sediment control are in place.

Smart Sponge® HM is the Abtech Industries media aimed at that gap. It targets dissolved metals including lead, zinc, copper, arsenic and selenium, along with phosphorus. We say it targets and binds these contaminants. We do not promise a removal rate, because results depend on the water, the flow and the loading at your site.

Media and Format: Keep Them Separate

Buyers often compare inserts as if the basket were the treatment. It is not. The media treats the water, and the format holds the media in the flow path. Our working principle is that the media follows the contaminant and the format follows the site.

Question	What decides it	Our offering
Which contaminant?	Dissolved metals, hydrocarbons, bacteria or phosphorus	Smart Sponge® HM for dissolved metals and phosphorus; standard Smart Sponge® for oil and hydrocarbons
Which fraction?	Dissolved or particulate	Media for the dissolved share; screening and settling for solids
Which opening?	Basin or curb inlet shape, size and design	Ultra Urban® Filter, custom-fabricated to fit
More than one pollutant?	Mixed sources on the same drainage area	Several media can be combined in one system

How Do You Fit a Filter to a Curb Inlet?

Curb openings, grated inlets and deck drains differ in geometry, and a generic basket can leave gaps where water bypasses the media. The Ultra Urban® Filter is custom-fabricated to each basin's shape, so it retrofits an existing structure without excavation. It is passive and high-flow, so it runs without pumps or power. Our guide to a stormwater pit and catch basin check before adding a filter covers what to measure, and our explainer on how Ultra Urban® Filter inserts and Smart Sponge® media work together covers the pairing.

Stainless steel Ultra Urban® Filter inserts carry a 20-year warranty. That warranty applies to stainless steel inserts only, and it covers the insert, not a promise about permit outcomes.

Where Heavy Metals Inserts Make the Most Sense

Metal recycling yards, fabrication shops and sites with equipment areas, where zinc, copper and lead repeatedly exceed MSGP benchmarks.
Paved catchments draining to municipal storm drains, where MS4 operators need treatment at many inlets without digging.
Airfields and transportation sites with large paved areas, where Ultra-Urban® Filter inserts were selected for an airport stormwater program treating deicing-season runoff.
Marinas, boatyards and shipyards, where washdown and dock runoff can carry metals toward the water.

For source patterns by site type, see our post on what causes heavy metals in stormwater.

What an Insert Cannot Do

An insert is a small treatment unit in a small structure. Swedish Hydro Solutions, which makes its own catch basin filters, states in its catch basin filter for stormwater systems page that a filter the size of a catch basin will not deliver as thorough treatment as a full-scale water treatment system. We agree with the principle. If a drainage area concentrates heavy loading in one place, or your effluent target is strict, a larger format may suit better. Bulk Smart Sponge® media can be loaded into vessels, skids, tanks and vaults, and Smart Pak®, Smart Bags and EOP units deploy media in vaults, channels and discharge points.

Not every format is passive. Smart Skid systems are installed with pumps, pressure and flow controls, so choose them knowingly when a site needs more than gravity can supply.

Why Inlet Treatment Has Research Behind It

Treating water at the inlet is not a new idea. The US EPA's final report on an upflow filter for treatment of stormwater at critical source areas describes a Phase II project that installed a prototype filter and monitoring equipment at modified inlets. It also ran laboratory tests of alternative media for flow capacity and particle retention. Those two questions, how much water passes and what the media holds, are the ones to put to any insert.

How We Approach a Site

Every project starts with a site assessment. For some projects we add laboratory column testing on your own water sample, with pilot testing for larger applications. If you are weighing a retrofit across many inlets, our post on catch basin retrofit stormwater treatment frames that decision, and you can schedule a site assessment to match media and format to your water.

After storms, inspect the grate and the insert and plan for removal of captured material by trained crews. Our catch basin insert maintenance after heavy rain checklist covers the surface steps.

FAQ

Does a sediment insert remove dissolved metals?

Not reliably. Sediment inserts hold solids and the metals attached to them. Dissolved zinc and copper need media built to bind them, such as Smart Sponge® HM.

Will an insert fit my curb inlet?

The Ultra Urban® Filter is custom-fabricated to fit a wide range of basin shapes, sizes and designs, so measuring the opening comes before choosing a format.

Does an insert need power?

The Ultra Urban® Filter is passive and runs without pumps or power. Smart Skid systems are different and use pumps and controls.

Can one insert treat metals and oil together?

Yes, in principle. Several Smart Sponge® media can be combined in one system, so a basin that receives dissolved metals and hydrocarbons from the same pavement can carry media for both. The site assessment decides the mix.