Biological Nitrogen Removal Database

A manually curated data resource for microbial nitrogen removal

Membrane Bioreactor

General Description

Membrane bioreactors (MBRs) are innovative biological wastewater treatment technologies that combine traditional aerobic/anoxic digestion with membrane filtration technology in biological wastewater treatment producing high quality effluent. They combine biological or enzymatic conversion and membrane separation. MBRs have a smaller footprint compared to traditional activated sludge processes and are an attractive choice for processing biodegradable organic matter in wastewater.

Basic Operation

The design of the MBR system varies depending on the nature of the wastewater and treatment goals. Typically, MBR system is made up of aerobic and anaerobic treatment tanks, mixers, aeration system, a flat sheet or hollow fiber ultrafiltration membrane, and either a membrane tank. In the treatment of wastewater that has a high concentration of nitrate an anoxic tank is added, where denitrification occurs. The filtration facility MBR system contains a high concentration of microorganisms (bacteria) that are held within the membrane. The concentration bacteria in the membrane reactor system is 4 to 5 times higher than the moving bed bioreactor and fixed bed bioreactors. A negative pressure is used in order to support the flow of wastewater through the membrane. This process is energy intensive and it is expensive to carry out. In some cases, chemical pumps are added to the system in-order to maintain a favorable optimum pH level and nutrient balance that is essential for a high efficiency in nitrate removal.

Biofilm carriers commonly used

Re-granulates of recycled plastics


Polyurethane beads

Polymeric sponges

Ceramic beads


Extractive membrane bioreactor

Sidestreamm membrane bioreactor (SMBR)

Immersed membrane bioreactor (IMBR)

  • Cost saving - Eliminate wastewater surcharges, reduce sludge handling and disposal costs, low sludge yield, save on chemical costs

  • Environmental friendly technology – ​it is possible to meet strict discharge limits for BOD, TSS, nitrogen, and phosphorus, produces a very high-quality effluent, suitable for water reuse, improves plant’s water security

  • Low operator attention requirements

  • Reduces or eliminates disinfection

  • It can be expensive to operate - membrane needs to be replaced occasionally and generation of the negative pressure that is required for influent flow through the system.

  • Time consuming - backwash of the membrane in set intervals is required and this system requires regular professional maintenance and servicing.

  • Higher capital cost than traditional activated sludge process

Applications of the bioreactor system

Municipal wastewater industries

Oil refinery wastewater

Petrochemical wastewater

Meat processing wastewater

Trialed Configurations/ Usage examples
  • BioprocessH2O, Boxborough, Massachusetts: MBBR was used for decentralized wastewater treatment. In order to meet the groundwater discharge permit requirements for total nitrogen, wastewater discharged from the Boxborough development was treated using an airlift membrane bioreactor (MBR) that utilized external tubular energy efficient membranes.

  • Evoqua designed a ADI system for membrane bioreactor treatment of biodiesel wastewater for Ag Processing Inc. (AGP), whic is a farmer-owned cooperative that produces biodiesel and they required an effective wastewater treatment system in-order to keep with production demands. The MBR installed by Evoqua can handle high strength wastewater with a flow-rate up to 8 500 gallons per day. This system was able to meet the effluent discharge objectives, allowing AGP to comply with the environmental regulations.

  • Evoqua installed an ADI system for membrane bioreactor treatment of biodiesel wastewater for Noosa Yoghurt Company, which produces a variety of delicious yoghurts in many flavors and sizes. In order to adhere to environmental regulations, they needed to discharge of their dairy wastewater using a reliable solution. The state-of-the-art MBR system installed at Noosa’s Yoghurt Company was effective in meeting the discharge limits of total nitrogen.

Further Reading