Analysis and Solutions for MBR Membrane Fouling
What is an MBR Membrane?
The MBR (Membrane Bioreactor) is a wastewater treatment technology that combines membrane separation technology with biological treatment processes. Compared to traditional activated sludge processes, the MBR process offers advantages such as superior effluent quality, a smaller footprint, and a high degree of automation. Therefore, it is widely used in municipal wastewater treatment, industrial wastewater treatment, and reclaimed water reuse.
However, MBR systems also face a core challenge in long-term operation: membrane fouling. Membrane fouling not only affects system operational stability but also significantly increases energy consumption and maintenance costs.
Main Types of MBR Membrane Fouling
During the wastewater treatment process, membrane fouling primarily manifests itself in the following ways:
1. Particle Blocking
Suspended solids and colloids deposit on the membrane pores, resulting in a decrease in water flux.
2. Organic Fouling
Soluble organic matter and microbial metabolites accumulate on the membrane surface, forming an organic film layer.
3. Biofouling
Microorganisms form biofilms on the membrane surface, increasing the transmembrane pressure (TMP).
4. Scaling
Crystallization and deposition of inorganic salts such as calcium, magnesium, iron, and manganese lead to a sharp decrease in membrane flux.
Problems Caused by Membrane Fouling
Decreased effluent flux: Insufficient treatment capacity.
Increased TMP: Increased energy consumption and shortened membrane life.
Increased O&M costs: Frequent physical and chemical cleanings are required.
Shortened membrane life: Accelerated membrane aging and high replacement costs.
Solutions to MBR Membrane Fouling
The following optimization measures can be taken to address membrane fouling:
1. Strengthening Pretreatment
Install fine screens, grit chambers, sedimentation tanks, or sand filtration to reduce suspended solids and large particles entering the membrane tank.
2. Controlling Operating Parameters
Reasonably control MLSS (generally 8–12 g/L).
Maintain appropriate sludge age (SRT) and dissolved oxygen (DO) levels.
3. Membrane Aeration and Flushing
Use a high-efficiency aeration device to utilize air-water shearing to mitigate membrane surface fouling.
4. Regular Cleaning
Physical Cleaning: Backwashing and air-water scrubbing.
Chemical Cleaning: Sodium hypochlorite (NaOCl), citric acid, etc., to target organic fouling and inorganic scaling.
5. Select Anti-fouling Membrane Materials
Use hydrophobic/hydrophilic modified membranes to improve their anti-fouling properties.