The MBR (Membrane Bioreactor)process flow and design calculation

The MBR (Membrane Bioreactor)process flow and design calculation

Summary

The MBR process is a key step in sewage treatment. Next I will introduce the MBR (Membrane Bioreactor)process flow and design calculation.

The MBR (Membrane Bioreactor)process flow and design calculation
The MBR (Membrane Bioreactor)process flow and design calculation
MBR Process Flow
The MBR (Membrane Bioreactor) process flow mainly consists of the following steps:
1. Pretreatment:
Wastewater entering the MBR system undergoes preliminary filtration to remove large solid impurities and suspended particles, reducing the burden on subsequent processing, usually using screens or sedimentation tanks.
2. Biological Reaction:
Pre-treated wastewater enters the bioreactor, where microorganisms in activated sludge degrade organic matter. A certain sludge concentration (MLSS) and dissolved oxygen (DO) are usually maintained to promote the removal of organic pollutants.
3. Membrane Separation:
After biological treatment, the wastewater undergoes solid-liquid separation through membrane modules (usually hollow fiber or flat sheet membranes). The membrane pore size is typically below 0.1 microns, effectively trapping microorganisms and most suspended solids.
4. Effluent Treatment:
The water treated by membrane separation, known as 'membrane permeate,' can usually be directly discharged or reused after further disinfection. The effluent quality can meet or exceed Class IV surface water standards.
5. Sludge Return:
Some concentrated sludge is returned to the bioreactor to maintain a certain concentration of activated sludge, supporting normal microbial metabolism. Excess sludge can be discharged or further treated as needed.
6. Cleaning and Maintenance:
The membrane modules are periodically cleaned both physically and chemically to prevent fouling and clogging, ensuring membrane flux and lifespan.
Design Calculation of MBR Capacity
The design and calculation of MBR system capacity typically involve the following steps and parameters to determine the number of membranes and system scale based on wastewater volume and inflow/outflow quality requirements:
1. Determine Treatment Water Volume
2. Calculate Membrane Area
Formula: A = Q / (J x 24)
3. Number of Membrane Modules
Formula: N = A / A_unit
4. Mixed Liquor Suspended Solids (MLSS)
5. Air Demand
Formula: Q_air = SADm x A
6. Control System and Cleaning Frequency
Calculation Example:
Assume: Daily treatment volume is 1000 m³/d, membrane flux J is 20 L/m²·h, and each membrane module area is 50 m².
1. Calculate total membrane area: A = 1000 / (20 * 24) = 2.08 m²
2. Calculate number of membrane modules: N = 2.08 / 50 ≈ 42 modules

Using these calculations, the number of membrane modules, aeration volume, and system configuration of the MBR system can be determined. In practice, adjustments are often made based on specific project requirements, influent quality, effluent standards, and membrane supplier data.