10 Benefits of Using MBR Membranes in Water Treatment

Membrane bioreactor (MBR) technology is commonly used when wastewater treatment requires guaranteed effluent quality with minimum space requirements. It uses biological treatment along with membrane filtration so that the membrane filters out biomass and suspended solids, while microorganisms are used to treat biodegradable pollutants.

The performance of a membrane is not the only factor in an industrial, municipal, commercial or decentralized project. Pretreatment, aeration, loading of the membrane, cleaning strategy and characteristics of the wastewater are all important. When working with the water treatment system supplier, it is important to ensure these elements function as one process; this can be achieved by selecting an experienced supplier.

A competent water treatment system manufacturer will be able to find the right membrane area, pumps, tanks, controls & treatment stages to fit actual circumstances, and a custom water treatment system can be used for limited space, variable flows or reuse objectives.

Let's explore 10 real-world advantages of MBR membranes in water treatment.

How MBR Membranes Work in Water Treatment

An MBR is a biological reactor in which the biological microorganisms are used to remove the biodegradable organic matter. Mixed liquor next comes into contact with microfiltration or ultrafiltration membranes. Water gets filtered through the membrane while the activated sludge and suspended solids are retained in the reactor.

This is a substitute for the secondary clarifier used in many conventional activated sludge plants. This has the benefit of improving control over biomass retention and the clarity of effluent because separation is no longer primarily based on gravity settling.

10 Key Benefits of MBR Membranes

1. Consistently Low Suspended Solids

The function of the MBR membrane is to prevent mixed liquor from coming into contact with treated water. “Maintains” is technically wrong in this context. The membrane retains the solids.

This helps to ensure effluent is consistently clear and is beneficial when downstream equipment is sensitive to solids or effluent discharge quality requirements are stable.

2. Smaller Process Footprint

Typically a biological treatment process, such as conventional activated sludge, must be followed by a secondary clarification process. But those large settling tanks may not be necessary when using MBR, which is a method of solid-liquid separation in which membranes are involved.

3. Higher Biomass Retention

With MBR membranes, the activated sludge remains within the biological system and is not discharged with the treated water. This can take place with a higher biomass concentration than is possible in many clarification-based systems.

This can provide more biological treatment capacity per unit volume of a reactor and can provide additional flexibility to reactor sizing and loading in the design phase.

4. Better Control of Solids Retention Time

MBR can achieve better separation of solids retention time (SRT) from hydraulic retention time (HRT) than conventional clarification systems. Water can pass through the process and microorganisms can reside in the reactor for a much longer time.

This reduces the amount of hydraulic residence time needed to obtain the desired biological treatment goals while maintaining a desirable microbial population.

5. Less Dependence on Sludge Settling

Good sludge-settling characteristics are important for secondary clarifiers. Solids carryover can increase due to bulking, hydraulic disturbances or change in wastewater composition.

Although MBR membranes do not eliminate the need for biological control, the final separation is significantly less dependent on the settling. This offers a more reliable barrier with sludge variability.

6. Better Preparation for Water Reuse

MBR effluent could be a very powerful feed stream for re-use systems because a large share of the suspended material is already removed. It may then be subjected to disinfection, activated carbon, reverse osmosis or other polishing.

The staged approach is important in that irrigation, cooling, process water and high-purity applications have varying water quality targets.

7. Better Use of Existing Tank Volume

MBR can be an appealing choice in retrofit scenarios where it may be hard to incorporate new biological tanks or clarifiers. This can sometimes enable existing reactor volume to be used at a higher intensity, due to higher biomass concentrations.

Checks still are needed on hydraulic capacity, oxygen transfer, membrane-tank design, pretreatment, piping, and sludge handling with a retrofit. The advantage is that process intensification does not necessarily imply a site extension.

8. Easier Modular Expansion

By nature, membrane systems are modular. Designers can decide on the number of membrane elements/skids based on flow, loading and operating flux and allow space for future expansion.

QILEE provides hollow fiber MBR membrane systems and modular membrane configurations for municipal, industrial, decentralized, and water reuse applications.

9. Suitable for Packaged and Containerized Treatment

Packaged or containerized treatment layouts are suited for MBR, as biological treatment and membrane separation can be integrated in a compact process train. Prior to delivery pumps, blowers, membrane modules, instrumentation, and controls can be integrated.

In addition, QILEE also packages MBR into combination systems with other wastewater-treatment technologies where necessary to provide pretreatment or polishing.

10 Flexibility in terms of integrating with other treatment stages.

MBR may be used for biodegradable wastewater and is not a one size fits all. Sometimes, before or after the biological stage, oils, high suspended-solids loads, toxic compounds, dissolved salts, or particularly challenging industrial compounds may need to be treated.

Depending on the wastewater, MBR can be coupled with screening, chemical treatment, dissolved air flotation, ultrafiltration, nanofiltration, reverse osmosis, disinfection, and sludge dewatering.

Choosing a Water Treatment System Supplier for an MBR Project

A Water Treatment System Supplier should begin with the characteristics of the wastewater, and not with a standard membrane package. Significant design parameters are average flow, peak flow, COD load, BOD load, solids, temperature, pH, oils, nutrients, effluent discharge requirements, reuse goals, and available space.

Then, membrane flux, air scouring demand, transmembrane pressure, cleaning, pre-treatment, instrumentation, sludge wasting and redundancy should be taken into consideration as part of the design.

In addition to UF, NF, RO and other wastewater-treatment processes, QILEE's water-treatment portfolio includes MBR membranes and integrated membrane systems. MBR can thus be considered as part of a complete treatment train rather than as a standalone treatment stage in situations where multiple stages of treatment are needed.

Conclusion

MBR membranes are especially effective for projects that require guaranteed suspended-solids removal, minimum land space, biomass retention or a solid foundation for water reuse.

MBR is not maintenance-free. Life cycle performance is negatively impacted by fouling, aeration energy, periodic cleaning, pretreatment, replacement planning, and operator capability.

For this reason, the choice of a water treatment system supplier, an experienced water treatment system manufacturer, or a custom water treatment system must always be based on real-world influent data and defined treatment targets. MBR technology can form a robust and flexible platform for wastewater treatment if the selection of membranes is combined with the appropriate biological design to fit the actual use cases.