What is Membrane Bioreactor (MBR) Technology?

Author: Ahmed Bakhiet – Project Manager – Coftec.

(i)  Introduction

Water purification is essential for maintaining the well-being of communities and ensuring the sustainability of industrial operations. Among the innovative approaches in this field, Membrane Bioreactor (MBR) technology stands out for its exceptional efficiency and effectiveness.  In this blog post, we will explore the world of MBR technology and briefly introduce Coftec’s modular Membrane Bioreactor solution. We will uncover the advantages of MBR technology in both municipal and industrial applications, highlighting its role in fulfilling environmental responsibilities and the potential of Membrane Bioreactor for wastewater treatment and process efficiency.

(ii)  What is Membrane Bioreactor Technology for Wastewater Treatment?

Membrane Bioreactor technology combines the principles of biological treatment and membrane filtration to achieve high-quality wastewater treatment. It integrates a biological process, typically an activated sludge process, with physical liquid-solid separation using membrane filtration. This unique combination allows for the efficient removal of contaminants, including suspended solids, pathogens, and dissolved organic matter, resulting in treated water of superior quality.

Below is a representation of a typical (submerged) MBR process flow diagram:

Figure 1: Process layout of a typical submerged MBR

• Influent Pumping & Preliminary Treatment: Wastewater influent, either from a municipal or industrial source, is pumped into the Membrane Bioreactor system. In some cases, a pre-treatment step may be included before the MBR process to remove large solids, debris, or other non-biodegradable materials. This can involve processes such as screening or grit removal to protect the MBR membranes from clogging or damage.
• Biological Treatment: The wastewater enters the biological reactor, which contains a mixture of microorganisms and activated sludge. In the reactor, organic compounds present in the wastewater are biologically degraded by the microorganisms through a process called biological treatment. The microorganisms consume the organic matter and convert it into carbon dioxide, water, and biomass. The biological reactor operates under aerobic conditions, ensuring an adequate supply of dissolved oxygen for the microbial community. This is essential for the growth and metabolism of aerobic microorganisms, enabling them to efficiently oxidize and degrade organic matter.
• Membrane Filtration: The bioreactor also contains the submerged membrane modules, which act as a physical barrier, selectively allowing the permeation of treated water (permeate) while retaining suspended solids, bacteria, and other contaminants.

Figure 2: Flow through an MBR membrane

As the feed water flows through the membranes, air is continuously supplied from the bottom of the membrane unit. This helps to scour off any sludge accumulating on the surface of the membranes during filtration.

• Permeate Collection: The permeate, or treated water, that passes through the membranes is collected and discharged for further treatment or reuse purposes. The quality of the permeate from the submerged Membrane Bioreactor system is typically of high clarity and low turbidity, meeting stringent effluent standards.
• Sludge Management: The biomass and activated sludge that are retained by the membranes form a concentrated sludge called mixed liquor suspended solids (MLSS). This sludge contains high concentrations of microorganisms and organic matter. Depending on the system design, a portion of the MLSS may be returned to the bioreactor to maintain the microbial population and treatment efficiency (Return Activated Sludge – RAS), while excess sludge may be wasted from the system (Waste Activated Sludge – WAS).
• Membrane Cleaning: Over time, the membranes can accumulate solids or foulants that may reduce their filtration efficiency. Periodic membrane cleaning is necessary to maintain optimal performance. This can involve various cleaning methods such as backwashing, air scouring, or chemical cleaning to remove accumulated solids or biofilm from the membrane surface.

(iii)  What are the Different Types of Membrane Bioreactor Membranes?

The main subtypes of MBR membranes include:

Figure 3: MBR configurations, (A) = Hollow Fibre, (B) Multi-tube, (C) Flat sheet

Hollow Fibre MBRs: This type of submerged MBR utilizes hollow fibre membranes, which are small, hollow tubes that allow for the filtration of wastewater. The mixed liquor flows through the interior of the hollow fibres, while permeate (filtered water) is collected outside of the fibres.

Figure 4: Example of a Hollow Fibre Membrane

Flat Sheet MBRs: Flat sheet membranes are used in this type of submerged MBR. The mixed liquor is pumped over the flat membrane surface, and the permeate is collected on the other side of the membrane.

Figure 5: Example of a flat sheet membrane

Multi-tube MBRs: In multi-tube MBRs, multiple tubes containing membranes are bundled together, creating a compact filtration unit. The mixed liquor passes through the tubes, and the permeate is collected on the outside of the tubes.

Figure 6: Example of a multi-tube membrane

 (iv)  What are the Benefits of Membrane BioReactor Technology?

• • • Enhanced Treatment Efficiency: MBR technology produces treated water of exceptional quality, surpassing stringent regulatory standards. It is superior to conventional wastewater treatment methods in terms of treatment efficiency and performance. The membranes effectively remove suspended solids, bacteria, viruses, and even certain pollutants, resulting in water that can be safely discharged or reused.

Figure 7: Typical effluent quality values for a CAS system vs. an MBR system

• • • Small Footprint: MBR systems have a compact footprint compared to conventional treatment processes. The membrane filtration component eliminates the need for secondary clarifiers, sand filters, and other large settling tanks. MBR systems typically require only a third of the space required by a CAS system.

Figure 8: Conventional Activated Sludge (CAS) System vs. Membrane Bioreactor (MBR)

• • • Enhanced Nutrient Removal: MBR technology facilitates the efficient removal of nutrients, such as nitrogen and phosphorus, from wastewater. This is particularly important in addressing environmental concerns related to eutrophication and water pollution. By incorporating additional treatment processes like biological nutrient removal (BNR) or chemical precipitation, MBR systems can achieve high levels of nutrient removal.
    • Tolerance to Fluctuations: MBR systems exhibit higher tolerance to variations in influent characteristics compared to traditional treatment methods. The robustness of MBR technology allows for reliable operation and consistent production of high-quality effluent, even under fluctuating influent conditions.
    • Potential for Water Reuse: With increasing water scarcity, the ability to reuse treated water is crucial. Permeate water from an MBR process is highly treated, and coliforms are significantly removed. This high-quality permeate is suitable for various non-potable applications like irrigation, industrial processes, and more. For Reverse Osmosis (RO) applications, the permeated water from an MBR system requires no further treatment before being fed into the RO process.

(v)  What are the Applications of Membrane BioReactor Technology?

MBR technology finds applications in various sectors, including:

• • • Municipal Wastewater Treatment: Many municipalities face the challenge of upgrading aging wastewater treatment infrastructure to meet stricter environmental regulations. MBR technology provides an excellent solution for enhancing treatment capacity and improving effluent quality without the need for extensive facility expansions. The compact footprint of MBR systems allows for easy integration into existing treatment plants, making the upgrade process more cost-effective and efficient.
    • Industrial Wastewater Treatment: MBR systems find extensive applications in various industries, including food and beverage, pharmaceuticals, and chemicals, where high-quality effluent is required for compliance with environmental regulations. Industrial wastewater can be highly variable in composition, containing a wide range of organic and inorganic contaminants. The ability to handle high organic loads and variable influent conditions makes MBR technology well-suited for industrial wastewater treatment.
    • Decentralized Wastewater Treatment: Many regions, particularly in developing countries or rural areas, lack the necessary infrastructure for centralized wastewater treatment. In such cases, decentralized systems become crucial for managing wastewater effectively.

MBR systems are modular and pre-fabricated, making them easily transportable and quick to deploy. This flexibility is particularly valuable in emergency situations, disaster-stricken areas, or temporary work camps where rapid installation and operation are essential. The modular nature of MBR systems also allows for easy scalability, enabling the treatment capacity to be adjusted based on the population size or wastewater volume.

(vi)  Introducing Coftec’s Modular Treatment Solutions with Membrane Bioreactor Technology.

Coftec stands at the forefront of modular treatment solutions, integrating MBR technology into our product offerings. Our expertise lies in providing scalable, flexible, and easily installable MBR treatment systems tailored to meet specific client requirements.

A Coftec modular Membrane Bioreactor plant offers numerous advantages when it comes to integration into an existing plant. The compact size and modular nature allows for easy scalability and expansion as needed.  The minimal civil work required for the installation of the modular MBR unit is another significant benefit of this technology.  It is possible for a modular plant to be rapidly constructed, transported, and installed, thus enabling swift deployment and reducing project timelines.

Figure 9: Example of Coftec’s Containerised MBR System

Coftec’s modular solutions leverage MBR technology to deliver high-quality effluent, optimize space utilization, and ensure reliable operation, even in challenging conditions. With Coftec, clients can trust in innovative and efficient wastewater treatment solutions that meet regulatory standards while prioritising sustainability.

(vii)  Conclusion

In conclusion, this blog post sets out a comprehensive exploration of membrane bioreactor technology and its implementation in Coftec’s modular water purification products. By diving into the advantages of MBR technology in both municipal and industrial settings, we aim to showcase the transformative potential of these innovative systems. Stay tuned as we embark on an enlightening journey to unravel the wonders of MBR technology and its role in shaping a cleaner, greener future.