In domestic MBR wastewater treatment, replacing clarifiers with membrane processes produces a high-quality effluent on a smaller footprint

A membrane bioreactor (MBR) is an advanced wastewater treatment technology that integrates membrane processes, including microfiltration or ultrafiltration, with a conventional activated sludge process. The MBR system comprises the following components:

  • A bioreactor: This is where the wastewater undergoes treatment using the activated sludge process, which is a biological process conducted under aerobic or anaerobic conditions. Microbes present in the activated sludge help to break down and oxidize organic pollutants present in the wastewater.
  • Membranes: The MBR system utilizes membranes to separate particles from the liquid component of the wastewater. These membranes function by filtration, clarifying the effluent and ensuring that the discharged liquid meets the required environmental standards for safety.

What Type of Membranes Are Used in Bioreactors?

In membrane bioreactors, there are three commonly used types of membranes: flat sheet, hollow fiber, and tubular/multitubular membranes. These membranes play a crucial role in the filtration process within the bioreactor.

Although both microfiltration and ultrafiltration membranes can be employed in membrane bioreactors, ultrafiltration membranes offer distinct advantages over microfiltration membranes. One notable benefit is their ability to effectively filter out smaller particles, including viruses. This finer filtration capability enhances the removal of contaminants from the wastewater, ensuring a higher degree of purification.

MBR in Wastewater Treatment Systems

In an MBR system, membranes serve the primary function of separating solid matter from liquid waste, which is typically performed by clarifiers in conventional activated sludge treatment processes.

A membrane bioreactor can be designed in two configurations: submerged membrane bioreactor (SMBR) and side-stream membrane bioreactor.

In the submerged configuration, the membrane is placed below the wastewater within the bioreactor. This setup utilizes vacuum-driven membranes to facilitate the separation of solids from the liquid component. The submerged membrane bioreactor allows for direct contact between the wastewater and the membrane surface, enhancing the filtration process.

On the other hand, and more common, is the side-stream membrane bioreactor. Here, the membrane is positioned outside the bioreactor and serves as an additional step to clarifying the wastewater after biological treatment. Pressure-driven membranes are employed in side-stream MBR systems, enabling efficient separation of solid particles from the liquid effluent.

Advantages of MBR in Wastewater Treatment

MBR technology offers numerous advantages over conventional wastewater treatment methods, including the following:

  • Reduced footprint: MBRs offer a significant advantage in terms of space requirements compared to conventional clarifiers. The chamber needed to house the membranes is much smaller, allowing for more efficient space utilization. Additionally, MBRs can sustain higher biomass concentrations, resulting in reduced sludge production and the need for smaller tanks to store the solid waste.
  • Fully-automated process: MBR technology provides a higher automated treatment process, requiring less manual intervention compared to conventional wastewater treatment systems. This makes MBRs well-suited for decentralized wastewater treatment plants deployed in remote locations where skilled operators may not be readily available. The automation capabilities ensure efficient and reliable operation, minimizing the need for constant supervision.
  • High-quality, pathogen-free effluent: MBRs excel in producing high-quality effluent that is free from pathogenic microorganisms. The membrane filtration effectively removes bacteria and viruses from the wastewater, resulting in purified water of superior quality compared to effluent produced by the conventional activated sludge process. This treated effluent can be safely discharged into the environment or reused for various purposes such as toilet flushing or irrigation of landscaping and recreational facilities. With further treatment using processes like reverse osmosis, MBR effluent can be utilized for a wide range of applications.

MBR Wastewater Treatment Applications

Membrane bioreactors are highly versatile systems designed to treat wastewater from diverse sources. They offer effective solutions for various applications:

  1. Municipal Wastewater: MBR technology excels in treating municipal wastewater, making it suitable for reuse purposes. With its compact footprint, MBRs are well-suited for decentralized applications where space is limited. They efficiently remove contaminants, producing high-quality treated water that meets the standards required for safe reuse.
  2. Industrial Wastewater: MBRs provide an effective solution for treating industrial wastewater that contains high concentrations of challenging organic and chemical pollutants. These pollutants can be difficult to treat using conventional methods. MBR technology combines biological treatment with membrane filtration to achieve excellent removal efficiency, ensuring compliance with stringent discharge standards.
  3. Specialized Wastewater: MBRs are valuable for treating specific waste streams, including landfill leachate. Landfill leachate often contains complex and high-strength contaminants that require advanced treatment. MBRs offer an efficient and reliable option for removing pollutants from landfill leachate, ensuring environmental compliance.
  4. Pretreatment for Challenging Wastewater: MBRs can also serve as a crucial pretreatment step for wastewater containing high levels of inorganic pollutants and heavy metals. By effectively removing suspended solids and contaminants, MBRs enhance the overall treatment efficiency of such wastewater, facilitating subsequent treatment processes.

FAQ

What advantage does submerged MBR offer over side-stream MBR?
Submerged MBR systems consume less energy compared to their use of vacuum-driven membranes. Unlike side-stream MBRs that require high-pressure pumping for cross-flow filtration, submerged MBRs rely on the suction effect, resulting in lower energy requirements.

Do MBR systems require any pre- or post-treatment?
The recommended pre-treatment measures for MBR systems depend on factors such as feed water quality, discharge regulations, and specific application. To safeguard the integrity of the membrane surface and prevent damage, it is advisable to screen the wastewater to remove debris and ensure the removal of oil and grease prior to MBR treatment.

How much maintenance do membranes require?
Regular membrane cleaning is essential to maintain optimal performance. The frequency of cleaning depends on the quality of the wastewater undergoing treatment.

What are the signs of membrane fouling?
Membrane fouling can lead to decreased trans-membrane pressure and recovery rate. In such cases, cleaning the membranes becomes necessary to restore and improve their performance.

Contact AUC Group to learn how our MBR systems, together with our flexible leasing plans, can help you efficiently and cost-effectively treat your wastewater stream to produce high-quality effluent suitable for reuse.