Membrane Bioreactor (MBR)
Membrane bioreactors (MBR) are systems that are highly effective in removal of organic, inorganic and biological contaminants from a wastewater stream. The system combines membrane filtration with a bioreactor as the title suggests. The system utilizes membranes submerged in the bioreactor with coarse bubble aeration to produce the mixing and reduce fouling. The process differs from a traditional wastewater treatment plant in that separation is not done by sedimentation in a secondary clarification tank but instead by membrane filtration.
MBR systems require a smaller footprint as compared to similar technologies and are a natural fit for industrial wastewater treatment.
Membrane Filtration
Membrane filtration is an enhanced form of filtration that can separate dissolved solids in wastewater. Pressure driven membrane processes from Micro-Filtration (MF) to Reverse Osmosis (RO) are specified with the respective pore size.
- Micro-Filtration (MF) can handle particulate or suspended solids from 0.1 to 10 microns.
- Ultra-Filtration (UF) recovers macro-molecules in the 0.01 to 0.1 μm range.
- Nano-Filtration (NF) removes particulate from 0.001 to 0.01 μm.
- Reverse Osmosis (RO) membranes separate materials less than 0.001 μm.
MF and UF membranes require pressure generally in the 0.1–10 bar range, while RO operation requires much higher pressure. The separation process generates permeate and concentrate streams.
Membrane cleaning is accomplished by frequent permeate back pulsing and occasional chemical backwashing. Anoxic or anaerobic compartments can be incorporated for simultaneous biological nutrient removal.
MBR Applications
Industrial wastewater streams typically contain high organic loadings in addition to difficult-to-treat compounds. The table below shows results achievable across several industries.
| Wastewater Source | Membrane Configuration | Treatment Efficiency |
|---|---|---|
| Paint Industry | Ultra-Filtration | COD Removal 94% |
| Food Industry | Micro-Filtration | Effluent TSS 9mg/l |
| Tannery Industry | Ultra-Filtration | COD Removal 94% |
| Cosmetic Industry | Ultra-Filtration | COD Removal 97% |
| Landfill Leachate | Ultra-Filtration | COD Removal 90% |
| Electrical Industry | Ultra-Filtration | COD Removal 97% |
MBR Advantages
- Smaller footprint required
- Higher effective sludge retention time (SRT)
- Lower sludge production
- Improved settling characteristics
- Operation at higher suspended biomass
- Ability to respond to load fluctuations
- Simple operation and maintenance
- Durable and stable
- No need for periodic backwashing
- Easily expanded as requirements change