Five Common Misconceptions About MBR Technology in Wastewater Treatment

1.Is Higher MBR Membrane Flux Design Always Better?

The membrane flux is determined by the material and structure of the membrane. For a specific membrane unit, there is an upper limit to its porosity and flux. Filtration is inherently a physical process—reducing pore size sacrifices throughput while balancing strength and long-term operational stability. Therefore, flux is a fixed value.During design and application, parameters recommended by membrane manufacturers should be followed.

2. Does MBR Technology Eliminate the Need for Sludge Discharge?

Due to the excellent retention effect of membrane filtration, the activated sludge concentration in MBR systems can reach high levels, decoupling hydraulic retention time (HRT) from sludge age. This eliminates concerns about sludge concentration affecting effluent quality.

However, this advantage only enhances biochemical performance and does not justify avoiding sludge discharge. Whether to discharge sludge depends on the condition of the activated sludge.

Without sludge discharge, activated sludge will age, degrading biochemical performance and affecting aeration efficiency. In practice, MBR systems can reduce sludge discharge but cannot eliminate it entirely.

3. Should Sludge Concentration Be Minimized to Prevent Membrane Fouling?

Membrane fouling is a common issue in MBR applications, often caused by sludge, especially at high concentrations. This leads to the misconception that lowering sludge concentration can prevent fouling.

However, both excessively low and high sludge concentrations accelerate membrane clogging. The correct approach is to maintain sludge concentration within an optimal range. Additionally, aeration plays a role in scouring the membrane surface and should be maintained at appropriate levels.

4.Is the Membrane Solely Responsible for Effluent Quality?

The membrane’s principle is physical filtration, primarily removing suspended solids (SS). Its role in MBR systems lies in enhancing biochemical performance, but it cannot filter soluble organic matter. Organic pollutant removal relies on the design and management of the entire treatment process.

5. Is MBR Only Suitable for Domestic Wastewater?

MBR technology combines activated sludge processes with membrane filtration, replacing traditional setups like activated sludge with secondary clarifiers. In this sense, MBR is applicable wherever activated sludge processes are used. However, for wastewater prone to membrane fouling, proper pre-treatment is essential.