Biological Nitrogen Removal Database

A manually curated data resource for microbial nitrogen removal

Packed Bed Reactor

General Description

Packed bed reactors (PBRs) are a popular choice of reactor design because of their high conversion rate per catalyst weight. PBR system has the potential to offer an effective and low-cost technology for upgrading the conventional wastewater treatment systems. PBRs can operate at up-flow, down-flow and horizontal modes.

Basic Operation

Packed bed reactor typically consists of a tubular or channel chamber that is packed or contains pellets, granular particles, porous ceramic or foam media and a liquid that flows through this bed of particles. The media is engineered to have a high enough surface area to encourage biofilm formation while also allowing wastewater to flow through the system. As the influent from wastewater passes or distributed through the layers of packed granular particles within column it interacts with the denitrifying microbes attached to the granular particles where they will have formed a biofilm, resulting in the removal of nitrate.

Biofilm carriers commonly used

Glass beads

Diatomaceous earth pellets

Polyurethane beads



Porcelain rings

Pumice stone




  • Packed bed creates anaerobic conditions favorable for denitrifying bacteria growth inside the column

  • High conversion per unit mass of catalyst

  • Low cost of construction, operation, and maintenance

  • More product is formed due to increased reactant/catalyst contact

  • Effective at high temperatures and pressures

  • High conversion rate per weight of catalyst

  • Easy to build

  • More contact between reactant and catalyst than in other types of reactors


Low tolerance for suspended solids

Undesired thermal gradients may exist

Pretreatment in some case is required for suspended solids

Poor temperature control

Channeling of gas stream can occur, leading to ineffective regions in the reactor

Post treatment sometimes is required depending on discharge limitations

Unit may be difficult to service and clean

Applications of the bioreactor system
  • Municipal wastewater industries

  • Oil refinery wastewater

  • Petrochemical wastewater

  • Meat processing wastewater

  • Trialed Configurations/ Usage examples
    • ClearFox project: Alte Schanze, Germany – Leachate from landfill contaminated with high nitrogen concentrations (NH4, NO2, NO3, various hydrocarbons – often organ halogens, chlorides, sulphates, different heavy metals (i.e. Zn, Cu, Ni, Cr, Cd, Hg, Pb and more). A packed bed reactor was used to treat and for the removal of nitrogen from the system together with sulfur from the system.

    • ClearFox project: Treatment of wood condensate wastewater, Thuringia, Germany – the packed bed reactor volume was 72 m³/d, it was used to treat wood condensate wastewater before the effluent was discharged into the environment.

    Further Reading