Membrane bioreactor (MBR system) for wastewater treatment

We design, manufacture and install membrane bioreactors for the treatment of industrial effluents. MBR reactors are compact, self-contained and easy to operate. Thanks to the use of membranes, there is no sedimentation in the biological tank.

MBR system: Biological reactor + membrane filtration

Membrane bioreactors, also known as MBR systems, are aerobic activated sludge biological reactors, which combine the biological degradation process, known as "activated sludge", with solid-liquid separation by membrane filtration. These membranes can be either hollow fiber or flat membranes.

Our MBR bioreactors are equipped with ultrafiltration membranes that maximize their efficiency and performance for contaminant separation. Thanks to this technology, the biomass concentration inside the reactor is much higher than that of reactors with conventional clarifiers, being possible to reach between 6,000 and 12,000 mg/L.

The combination of the membranes and the activated sludge reactor has the following advantages:

  • Higher performance in the elimination of organic matter.
  • The quality of the output water is constant.
  • Compact equipment that occupies a small footprint.

Our membrane bioreactors are delivered in a compact system and ready to operate upon arrival at the customer's facility.

Optional configuration

In scenarios where there is a high nitrogen concentration and/or nitrates are generated above the discharge limits, a modified SIGMA MBR system with an anoxic pre-chamber will be offered. This configuration allows the simultaneous removal of COD and nitrogen by nitrification-denitrification.

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Purification efficiency of MBR systems

Our membrane bioreactors offer high efficiency for both domestic and industrial wastewater. Each unit is designed according to the characteristics of the incoming wastewater.

The following table shows the pollutant removal efficiency, which is very high and consistent.

COD (mg/L)<600<4093%
BOD (mg/L)<300<1097%
TSS (mg/L)<300<299%
TSK (mg/L)<40<1075%
Escherichia coli (CFU/100 mL)90-100%
Legionella ssp (CFU/100 mL)90-100%
Oils and fats (mg/L)<50<198%

3D animation of our MBR system

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What are the advantages of an MBR system?

A membrane bioreactor offers numerous advantages over conventional wastewater treatment systems:

  • By installing a membrane filtration process together with an activated sludge reactor, a higher organic matter removal performance is obtained.
  • The quality of the output water is higher and remains constant.
  • Compact plant
  • Volume and reduced spaces.
  • Simple treatment. Process management is simple and economical because there is no sedimentation in the biological tank.
  • Resistance to oxidizing agents
  • Simplicity of operation, since the operator only has to control the operation of the permeate and recirculation pump and the working pressures. The working parameters are controlled by a PLC with the possibility of remote connections via MODEM.
  • Stability and flexibility
  • Modularity
  • Standardization

Thanks to our MBR systems, very high quality treated water is obtained and can be reused in numerous industrial production processes.

Installation of an MBR system

Our membrane bioreactors can be installed in ISO containers, facilitating transport, assembly and, eventually, subsequent expansions.

  • Quick plug&play installation
  • Low space requirements
  • Does not emit odors or attract carriers such as insects.
  • High load volumes
  • Disinfection without UV or chemicals
  • Effluent suitable for agricultural use, or for reuse in toilet flushing water.
  • Fully automated process
  • Modular expandability

Technical information

SMBR 50501100021502200GRAVITY10060450030000
SMBR 1001001100021502200GRAVITY100120450030000
SMBR 1501501100021502200GRAVITY100180450030000

Filtration membranes

Our MBR systems include KUBOTA brand ultrafiltration parallel flat membranes, which are vertically submerged in the aeration chamber, inside the mixed liquor.

Air is blown from the bottom of the membranes into the container, which on the one hand creates the overpressure of the medium on the membrane, and on the other hand keeps the biomass in motion to prevent the formation of a layer of microorganisms (a term known as 'biofouling') blocking the membrane. A permeate pump continuously extracts the water that has been treated on the inside of the membrane.

The membrane film is made of chlorinated polyethylene and has a maximum (nominal) pore size of 0.4 μm and an average size: 0.2 μm, which blocks almost all microorganisms in the mixed liquor.

The "flat plate" configuration keeps the space between the membranes clear and minimizes debris accumulation.

Submerged membranes separate the liquid part from the solid part. The liquid fraction is sent to a storage tank while the solids are recirculated to the aeration zone.

Operation of our membrane bioreactors

Inside the reactor, the aeration system provides oxygen to the aqueous medium. Under these conditions, the microorganisms degrade and eliminate the organic matter present in the wastewater. The aeration system, in addition to providing oxygen, allows the reactor to maintain homogeneous mixing conditions.

It is very important not to introduce fats, oils and hair remains in this type of reactors, so it will be necessary to install an appropriate pretreatment to avoid these elements.

The membranes are located vertically in the aeration chamber, submerged in the mixed liquor. In this way, the mixed liquor (a mixture of water and the solids that make up the biomass) is directly in contact with the membranes and clarification is carried out simultaneously. The membranes suck the wastewater by means of a self-priming centrifugal pump.

Air is blown from the bottom of the membranes into the container, which keeps the biomass moving to prevent the formation of a layer of microorganisms blocking the membrane. A permeate pump continuously extracts the purified water in the inner part of the membrane.

After the solid-liquid separation carried out in the membranes, the low molecular weight contaminants are sent to a storage tank, while the solids are sent back (recycled recirculated) to the aeration zone.

In the passage of the wastewater through the membrane, the physical separation of water and biomass takes place:

  • The permeate, consisting of water, salts and low molecular weight non-biodegradable substances, leaves the system through the top of the membranes.
  • The concentrate, consisting of biomass and organic substances of higher molecular weight, is retained and remains inside the reactor to continue biological degradation.

Sludge generation from this type of reactor is minimal and requires occasional blowdowns.

In scenarios where there is a high nitrogen concentration and/or nitrates are generated above the discharge limits, a modified MBR system with an anoxic pre-chamber will be offered. This configuration allows for the simultaneous removal of COD and nitrogen by nitrification-denitrification.

Importance of diffusers

Diffusers or aeration systems are an essential part for the correct operation of a biological reactor. These systems allow the introduction of air, and therefore oxygen, into the reactor in the form of fine bubbles. This bubble size favors the contact area of the air with the biomass, which uses oxygen, and the efficiency of organic matter degradation. In addition, this bubble injection allows a homogeneous agitation of the mixed liquor, without disturbing or breaking the microorganisms.

Therefore, the efficiency of wastewater treatment depends directly on the efficiency of the diffusers and their correct design and installation.

Membrane maintenance and washing

The correct maintenance and cleaning of the membranes inside the bioreactor is essential to ensure maximum efficiency and performance of the MBR system.

Before deciding which washing system is the most appropriate, it is important to know the rate and type of fouling that occurs in the membrane bioreactor.

Some factors that influence fouling are membrane characteristics (material, configuration, pore size and distribution), operating conditions (permeate flux, cross-flow, aeration and retention time) and biomass properties (viscosity, temperature, dissolved oxygen, floc property, sizes, etc.).

Air Washing

This process combines backwashing with an air stream that is sent through nozzles located in the center of the membrane bundles.

The air bubbles will travel across the outer surface of the membranes performing a flushing action that removes any solids that may have accumulated on the membrane surface.

The air filtration and washing operation is controlled by a computer, in which predetermined time cycles are programmed. This pressure/vacuum process is monitored and controlled in the membrane system. 

Chemical washing

Over time, organic matter and biomass accumulate in the pores and on the outer surfaces of the membranes, requiring more thorough cleaning.

This is achieved by chemical washing in which the membranes are backwashed, or immersed in a cleaning solution containing a solution of dissolved chlorine, citric acid, caustic soda or detergent.

This deep cleaning is configured according to the operating conditions of each specific case.

We offer an "in situ" washing system, which is supplied with the plant itself to allow automatic washing in the plant itself without the need to remove the membrane modules from the tank.

The sludge or residual sludge from cleaning is sent out of the equipment for final disposal.

MBR bioreactor applications

The applications of membrane bioreactors are very wide. In Sigmadaf we have carried out installations in a wide variety of industries, as well as in more special applications:

  • Industrial Processes
  • Municipal water
  • Military camps and humanitarian missions
  • Hotels and resorts
  • Buildings such as hospitals or shopping centers


  • Capacity: 200 - 500 inhabitants
  • Weight: less than 1.2 ton
  • Transportable by helicopter

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