Membrane bioreactor (MBR) technology is a highly effective wastewater treatment process that combines two fundamental treatment steps: biodegradation, membrane filtration, chemical and enzymatic degradation, and membrane filtration. The outcome is a streamlined method as compared to the conventional wastewater treatment strategies. MBR technology is used in many fields such as municipal wastewater treatment, industrial use, and even in small systems like a hotel or a resort. In this blog, the author will also endeavor to discuss MBR membrane bioreactors, their constituents, using MLSS and SRT, its benefits, and ‘real world’ application.
1. What is an MBR Membrane Bioreactor?
An MBR membrane bioreactor is a wastewater treatment technology that combines both biological and membrane methods of water purification. This change of process eliminates the sedimentation process and can offer a more efficient and more compact means to purify water.
There are two main types of MBR configurations:
- Submerged (immersed) MBR systems: Membranes are immersed in the bioreactor, and vacuum is created to draw the treated water through membranes.
- External (side-stream) MBR systems: The membrane modules are external to the bioreactor and the high-pressure solids are pumped through the membranes.
2. Understanding how the MBR process works entails the following steps:
The MBR process primarily consists of two components:
Biological Treatment: In an MBR, the biological process is similar to the activated sludge process where microorganisms decompose organic compounds in water. Air is supplied to the bioreactor to enhance the activities of aerobic microorganisms capable of breaking down the said pollutants and nitrogenous substances.
Membrane Filtration: Following biological treatment, the effluent is subjected to membranes that work as filters. These membranes are normally composed of polymeric or ceramic materials and are well suited for capturing of suspended solids, bacteria and viruses.
3. Key components of an MBR System:
- Bioreactor: This is the phase where the biological deterioration of the contaminants occurs.
- Membrane Modules: These are used for filtering the treated water and are manufactured either in the form of hollow fibers, flat sheets or tubes.
- Aeration System: Supplies the required amount of oxygen to the microorganisms inhabiting the bioreactor and minimizes fouling of the membrane interface due to the development of turbulences.
- Permeate Pump: Removes and collects the treated water (permeate) from the membrane module.
- Cleaning Systems: From time to time fouling takes place and this warrants the cleaning of the membranes. Cleaning methods may involve chemical washing, back washing, or even physical washing methods such as air agitation.
4. Advantages of MBR Systems
The MBR membrane bioreactor technology offers several advantages over conventional wastewater treatment methods, making it an attractive solution for many applications:
High-Quality Effluent: This process integrates biological treatment with membrane filtration, resulting in water that is very purified and free from suspended particles and other pathogens. This makes the water acceptable for other uses like irrigation, industrial use and in some cases, direct consumption.
Compact Footprint: MBR systems take up less space as compared to conventional treatments such as activated sludge. This is because membrane filtration eliminates the need for a huge secondary clarifier and the system can work at higher SL duty biomass levels.
Flexibility and Scalability: HINADA’s MBR systems can be expanded or shrunk to meet the treatment capacity needs of large municipal plants to tiny houses and apartment buildings.
Reduced Sludge Production: MBR systems are more efficient in removing sludge than the normal treatment systems; hence, the need to dispose of sludge is limited.
Consistent Performance: The membrane barrier makes it possible that the quality of the treated effluent should be stable irrespective of the quality of the influent water.
5. Assessing Workability Issues and Possible Remedies in MBR Systems
However, like most treatment processes, MBR membrane bioreactors also have some drawbacks, more notably associated with costs of operation and membrane fouling.
Membrane Fouling: Membrane fouling is one of the major issues associated with MBR systems that involve the accumulation of independent particles, microorganisms or other organic matter on the surface of membrane. To combat this, MBR systems use various cleaning strategies, including:To combat this, MBR systems use various cleaning strategies, including:
Air Scouring: Stirs air into the solution to provide turbulence that assists in removing foulants from the surface of the membrane.
Chemical Cleaning: Sometimes, these membranes are chemically cleaned using solutions such as sodium hypochlorite or citric acid in order to strip the foulant layer.
Energy Consumption: MBR systems are known to consume a lot of energy especially in the processes of aeration and membrane filtration. Although membrane concentration polarization and fouling represent major challenges to the energy efficiency and overall feasibility of membrane distillation, progress in the membrane materials, system design, and operating techniques has enhanced energy efficiency of the system.
Cost: It can be considerably more expensive to install an MBR system in comparison to that of a traditional plant. However, the smaller size, lower cost of sludge disposal and high quality of effluent which is normally produced may pay off in the long-run.
6. Applications of MBR Technology
MBR membrane bioreactors are used in a wide variety of applications, including:
Municipal Wastewater Treatment: MBR systems can also be employed especially in MWWT plants that have given emphasis on the use of limited space and where water reuse is given importance.
Industrial Wastewater Treatment: Most industries like the food and beverage, the pharmaceutical, and textile manufacturing industries rely on MBR systems to treat their wastewater to match regulatory discharge standards.
Water Reuse Projects: Due to the characteristics of effluent being highly treated in MBR systems, they are suitable for water reclamation purpose, including irrigation water, industrial water, and even drinking water after further advanced treatment.
Decentralized Wastewater Treatment: MBR systems are ideal for the decentralized treatment of wastewater in small towns and villages, hotels and resorts, and any other areas where centralized treatment plants cannot be put in place.
Conclusion
The MBR membrane bioreactor is one of the most effective and efficient techniques for wastewater treatment with many advantages including high quality of developed effluent, relatively small area required for its construction, and low sludge generation. Despite the aforementioned drawbacks, especially the membrane fouling problem and high energy demand, continuous improvement of MBR technology can make MBR systems more practical and applicable for various fields. There remains the need to come up with better solutions for MBR membrane and this is something that companies like HINADA are now developing to meet the increasing demand for effective wastewater treatment.
