Filterra® Biofiltration

Filterra is similar to bioretention in its function and application, but has been optimized for high volume/flow treatment and high pollutant removal. Its small footprint allows it to be used on highly developed sites such as landscaped areas, parking lots and streetscapes. Filterra is exceedingly adaptable and can be used alone or in combination with other BMPs. The Filterra® Bioretention System has been verified in accordance with ISO 14034 Environmental Management - Environmental Technology Verification (ETV).


  • Low Impact Development and Green Infrastructure Design
  • High pollutant removal requirements
  • New construction and urban retrofits
  • Pretreatment for above-ground or shallow below-ground storage
  • Shallow (1.3 m), decentralized treatment
  • LEED points

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Filterra – High Flow Rates, High Pollutant Removal

How Filterra Works

  1. 1. Stormwater runoff enters the Filterra system through a curb-inlet opening and flows through a specially designed filter media mixture contained in a landscaped modular container. The filter media captures and immobilizes pollutants; some of these pollutants are then decomposed, volatilized and incorporated into the biomass of the Filterra system’s micro/macro fauna and flora. Stormwater runoff flows through the media and into an underdrain system at the bottom of the container, where the treated water is discharged.
  2. 2. The standard configuration utilizes a downstream catchbasin for bypass flows allowing the shallowest profile
    (typical 1.3 m) and most flexible design.


Filterra Features and Benefits

Features Benefits
Multiple third party field tests confirmed that Filterra achieves verified pollutant removal under TAPE and TARP testing Verified Performance
Filterra offers the most cost effective stormwater treatment system featuring easy installation and simple maintenance Value
Landscaping enhances the appearance of your site making it more attractive while removing pollutants Aesthetics
Available in multiple configurations, sizes and shallow profile (1.3 m) Flexible
No confined space access. Activation and first year of maintenance is included with the purchase of every system Simple and easy maintenance
Obtain up to 12 points for LEED Certification LEED


  • Standard (offline)
  • Street Tree
  • Recessed Top
  • Internal Bypass
  • Roof Drain
  • Custom Configurations
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    Filterra Media – Proven Pollutant Removal

    At the heart of the Filterra system is Filterra engineered biofiltration media; a specified gradation of washed aggregate and organic material homogeneously blended under strict quality controlled conditions. Using data from independent, third-party studies including the University of Virginia (TARP), Herrera Environmental Consultants (TAPE), Terraphase Engineering (NJCAT), North Carolina State University (TAPE & TARP) and Geosyntec Consultants, the filter media has been optimized to operate under high flow rates while maintaining pollutant removal performance. Filterra media is tested for hydraulic functionality, fertility, and particle size distribution to ensure uniform performance.

    Filterra media also supports a vegetation component with suitable hardiness for the local region consisting of grasses, shrubs, or trees that assist with the adsorption of pollutants with biological uptake/storage and pollutant consumption by microbes within the plant root zone.

    Pollutant Median Removal Efficiency Median Effluent Concentration (mg/L) Third Party Reference Studies
    Total Suspended Solids 86% 3.3 UVA 2006, Herrera 2009, Herrera 2014, NC State 2015
    Total Phosphorus (TAPE) 70% 0.05 Herrera 2014, NC State 2015
    Total Nitrogen 34% 0.54 NC State 2015
    Total Copper 55% 0.004 UVA 2006, Herrera 2009
    Dissolved Copper 43% 0.003 Herrera 2009
    Total Zinc 56% 0.04 UVA 2006, Herrera 2009, NC State 2015
    Dissolved Zinc 54% 0.1 Herrera 2009
    Total Petroleum Hydrocarbons 87% 0.71 Herrera 2009

    Information above is based on results from third party field studies following industry recognized protocols such as TAPE and TARP. Relevant studies are noted for each pollutant, and corresponding data was aggregated to provide realistic and repeatable performance expectations.


    Based on more than 20 years of research and development, quality control, testing and field monitoring, Filterra’s water quality treatment performance has been recognized by some of the most significant regulatory agencies, including the states of: Washington, Virginia, Maryland and New Jersey, the District of Columbia, the Texas Commission on Environmental Quality and the Atlanta (GA) Regional Commission. Highlights regarding these approvals include:

    • Granted ESD (Environmental Site Design) status by the state of Maryland Department of the Environment (MDE)
    • GULD-approved for ALL pollutants of concern with the state of Washington Department of Ecology (WA ECOLOGY) with (2) TAPE field tests
    • Third-party nationally recognized field/lab tests completed: (1) TARP, (2) TAPE, (1) NJCAT and (1) NC-DENR

    Installation and Maintenance

    We make it easy for you...

    • Vegetation selection guidance based on your climate zone and salt tolerance.
    • On-site planting and activation included with every system.
    • The first year of maintenance is included with the purchase of every system.
    • Ongoing maintenance is simple:
    • - No confined space entry required, everything can be accessed from the surface.
    • - Clean biofiltration bay with simple landscape tools (rake and shovel).
    • - Replace hardwood mulch.


    Bioretention systems such as Filterra rely on the vegetation to assist in pollutant removal. Winter road clearing efforts can wreak havoc on roadside landscaping and stormwater structures.

    For the best performance, Imbrium recommends the following:

    • Use salt tolerant plants. Refer to Imbrium’s recommended plant list for Filterra systems
    • Consider using taller vegetation for increased visibility during large snow events, and suitable system placement to avoid plows and snow piling
    • Perform maintenance at the end of winter, and flush the plant with water to washout remaining salt

    How Filterra Works

    Filterra is offered in multiple configurations to meet site specific needs. These configurations make Filterra a versatile yet effective stormwater BMP with a low life-cycle cost.

    Filterra Standard Offline
    The Filterra Standard Offline configuration is the most economical and simplest Filterra configuration. It utilizes a downstream catchbasin or curb inlet for bypass flows allowing for the shallowest profile and most flexible design of any of the Filterra configurations. It is ideal for both new and retrofit projects.

    Filterra  – Street Tree 
    The Filterra Street Tree contains openings in the concrete vessel for root expansion of trees with larger root balls.

    Filterra – Recessed Top
    Filterra recessed tops allow a seamless integration using pavers, Mulch, or sod. Recessed tops increase the depth of the invert out.

    Filterra Internal Bypass - Pipe
    The Filterra Internal Bypass – Pipe treats stormwater runoff from rooftops or other sub-grade sources such as area drains. Higher flows bypass the biofiltration treatment system via an overflow/bypass pipe design.