1. Membrane Tank Water Level Control
The water level in the membrane tank should be maintained 500–1000 mm above the membrane module frame.
A low water level may cause membrane drying and suction issues, while an excessively high level can weaken the scouring effect of aeration on the membrane surface.
2. Aeration Conditions
The ratio of aeration flow to permeate flow should be controlled within 12–20:1.
The aeration water level should be kept 50–60 mm higher than the surrounding liquid level to ensure uniform aeration in the membrane zone.
3. Sludge and Water Quality Conditions
The MLSS concentration in the membrane tank should be maintained at 5000–8000 mg/L.
The optimal operating temperature is 15–35°C, and the pH should remain within 5.5–9.0.
The sludge volume index (SVI₃₀) should be controlled within 20–30% to ensure good sludge settleability and biological characteristics.
4. Cleaning and Maintenance
Perform routine water flushing of the membranes every 2–3 days, and no longer than one week.
Backwashing flow should be twice the design permeate flow, with a typical backwash duration of 10 minutes.
Aeration should not be stopped during flushing.
Backwash water should pass through a security filter with 1 µm precision.
5. Transmembrane Pressure (TMP) Control
The TMP for membrane system operation generally ranges from 10–50 kPa.
When TMP reaches 50 kPa, a chemical cleaning should be performed to prevent further membrane fouling.
6. Pretreatment Requirements
Pretreatment aims to remove large solids that may damage the membrane, such as fine fibers or hair.
A rotary mechanical screen with openings smaller than 1 mm is typically installed at the raw water inlet.
7. Material and Model Selection
Membrane material and model should be selected based on treatment needs.
PVDF is widely used due to its excellent chemical stability and mechanical strength.
Common membrane configurations include hollow-fiber, flat-sheet, and tubular membranes, each offering distinct advantages depending on application conditions.
8. Anti-fouling Performance
Choosing MBR membranes with strong anti-fouling capabilities is critical.
Advanced MBR membranes often incorporate specialized surface treatments, such as nanocoatings or hydrophilic modifications, to enhance anti-fouling performance and prolong service life.