Fluidized Bed Reactor (FBR)

The Technology

The Envirogen Fluidized Bed Reactor, or FBR is a proprietary biological active water treatment system used to remove nitrate, selenium, perchlorate, and other difficult contaminants from water. Based on the contaminant to be removed, the fluidized bed bioreactor can be customized with various media, microbes, nutrients, and electron donors. In the FBR process, the objective is to feed and grow a specially selected microbial biomass on the FBR media. The result of the fluidized bed reactor design is that these microbes then consume/degrade the target contaminant/compound.

  • FBR Process: An active water treatment process that utilizes microbes growing on a fluidized media bed to degrade or consume difficult contaminants.
  • Fluidized Bed Bioreactor: Uses microbes, grown on a fluidized media, to transform toxic contaminants.
  • Fluidized Bed Reactor: Is a green solution to contaminated water that uses microbes to degrade and consume harmful contaminants.
  • Fluidized Bed Reactor Design: Involves the critical system sizing and the selection of specialty microbes that can degrade or consume a targeted water contaminant such as nitrate, selenium, or perchlorate.

The team at Envirogen has a long history of harnessing the science of microbiology to produce high-performance Fluidized Bed Reactor (FBR) systems engineered to eliminate even the most difficult chemicals, such as selenium, nitrate, perchlorate, BTEX and many other, from aqueous streams, providing high-quality, potentially recyclable water and potable water. In fact, we successfully installed a Fluidized Bed Reactor System to treat perchlorate contaminated wells in Southern California, and obtained regulatory approval to deliver potable water to the local communities. Using non-pathogenic, naturally occurring bacteria, and nutrients to facilitate bacteria growth, the Fluidized Bed Reactor transforms toxic contaminants so they can be safely removed, thus delivering a green solution to address difficult contaminants.

US Patents: 6706521, 5750028, 5788842, 7754159, 7611890, 7572626, 8323496, 6830922

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Our Product

For a broad range of influent flow rates and contaminant concentration levels, our Fluidized Bed Reactor (FBR) system is often the most economical treatment choice. With aerobic, anaerobic and anoxic designs available, systems have been successfully operated at ranges from 5 to 6,000 GPM, yielding high performance paired with low capital and operating costs.


Small footprint/Efficient – High concentration of biomass, plug-flow characteristics and tall beds minimize bioreactor footprint. High biomass concentration means long Solid Retention Time (SRT) and short Hydraulic Retention Time (HRT) and a high-quality effluent

Steady-state performance – FBRs run continuously without backwashing or cleaning operations.

Proven design – Envirogen’s Fluidized Bed Reactors have been continually improved and refined based on lessons learned over 30+ years of design and operating experiences.

Robust – Does not plug up or channel. Tolerant of high feed Total Suspended Solids (TSS) and metals. Proven robust performance and ability to quickly recover from upsets such as power outages or loss of chemical feeds. Capable of handling both hydraulic and organic shock loads.

Flexible – Operates effectively over a wide range of feed flow and qualities. Actual treatment technology (“green”), not just a phase transfer treatment for most contaminants.

Cost effective – Envirogen’s Fluidized Bed Reactors are cost effective across a wide range of contaminants treated


Whatever the problem – chemicals, aromatics, alcohols, ketones, chlorinated solvents, Polycyclic aromatic hydrocarbons (PAH), 1,4-Dioxane, chromium hydrocarbons, BTEX (Benzene, Toluene, Ethylbenzene and Xylene), selenium, perchlorates or nitrates – the FBR system handles high flows at low cost with typical treatment efficiencies of 99 percent or higher.

Additionally, this is one of the most efficient denitrification processes available today. Our FBR denitrification process lowers discharge levels of nitrogen in wastewater to less than 0.1 mg/l NO3-N. This simple end-of-pipe solution can use different carbon sources, does not require backwashing, produces minimal biosolids, and does not have filter upsets due to accumulating nitrogen bubbles.

One application where the FBR is well suited is for denitrification of the Flue Gas Desulfurization wastewater produced in coal fired power plants.  Specifically, Envirogen’s FBR can be inserted into existing chemical precipitation processes (as depicted in the image below) to reduce the nitrate load on the downstream biological system, thereby improving selenium compliance. Removing nitrate up-front can also reduce the size and cost of downstream biological treatment.  Read more about our experience in Power Plants.

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Fluidized Bed Reactor Frequently Asked Questions

Q: How does a fluidized bed reactor work?
When used to treat contaminated water, the fluidized bed reactor uses up flowing water to suspend or fluidize the media. This media supports the growth of specially selected microbes that act to degrade or consume toxic contaminants such as selenium, perchlorate, nitrate, 1,4 dioxane, and others.
Q: What is a fluidized bed used for?
Although commonly used to facilitate chemical reactions, fluidized beds are also used as an active water treatment system to remove recalcitrant contaminants. The Envirogen fluidized bed reactor uses specialty microbes, grown on a fluidized media, to transform toxic contaminants so the effluent can be safely discharged.
Q: What is the difference between fixed bed and fluidized bed?
In a fixed bed system, the media bed is packed together and not moving. In a fluidized bed, water flows at a set flow rate to cause the media bed to hydraulically rise, where it remains in this fluidized state during treatment. By fluidizing the media, all the media surface area is exposed and available for the task of removing harmful contaminants.
Q: What are the advantages and disadvantages of a fluidized bed reactor?
Fluidized beds used in water treatment applications tend to have smaller footprint/overall system size then fixed bed counterparts. In addition the system can run continuously without backwashing. If forward feed needs to be stopped, the microbes remain fluidized in the reactor and can be maintained in a “ready state” to initiate treatment once feedwater is restarted. A potential disadvantage of this technology is that additional electrical costs might be incurred to operate the system continuously in a fluidized state. However, this cost is often offset by the numerous advantages previously conveyed.

Envirogen Experience