Stormwater Trash Separators

In a Nutshell

Stormwater trash separators, also known as gross pollutant traps or hydrodynamic separators, are devices which are used in order to separate pollutants and trash from stormwater as the flow passes through the device.

Practical Solution

The “How To”The “How To”

Gross pollutant traps are filters which catch stormwater pollution before it is able to enter into waterways. They catch most of the litter and silt but are not able to stop chemicals from escaping into the environment. These contents collected from the stormwater must be emptied on a regular basis and then sent to a landfill.

Items which are considered to be gross pollutants include:

  • Domestic Plastics, including plastic bags or clingwrap
  • Industrial Packaging
  • Metals
  • Plastic Bottles
  • Paper Products including Cigarette Butts
  • Sediments
  • Organic Materials such as grass and garden clippings

Further information on gross pollutant traps can be found here.

Planning & ZoningPlanning & Zoning

Hydrodynamic separators are a fairly new technology, and due to this, few ordinances have adopted their use into zoning codes. Of the few codes that do consider the use of these separators, they have tended to be included in codes with other environmental best practices such as bioswales. In the St. Louis region, the Metropolitan Sewer District will not maintain the devices unless they are approved separators.

Dollars & CentsDollars & Cents

The cost of a hydrodynamic separator varies greatly depending upon the size of the unit in addition to the model type. Capital costs for the units range from approximately $4,000 to roughly $300,000. Labor and installation costs can be 50-100% of capital costs.

The city of Los Angeles, California in 2003 estimated that the cost of 40 units and maintenance for 10 years would cost roughly $30,000,000. More information on the California plan can be found here.

Measuring SuccessMeasuring Success

The success of installing hydrodynamic separators can be easily noticed based upon the condition of stormwater as it is being treated. With proper implementation, the stormwater should be free of large suspended solids and also oils. The benefits of the use of these devices can also be seen in the treatment costs of the region which is utilizing them. If the devices are proving effective, then the treatment cost for the region should decrease.

Case StudiesCase Studies

Discover MoreDiscover More

Basic information on hydrodynamic separators can be found here.

Information on the FloGard Dual Vortex brand hydrodynamic separator can be found on the item manual.

Information on the Aqua-Swirl hydrodynamic separator can be found on the AquaShield page on them.

The Vortechs Stormwater Treatment hydrodynamic separator information can be found here.

The State of Connecticut drafted an approved list of hydrodynamic separators. That list can be found here.