MBR Technology: The Platinum Standard for Sewage Treatment
Membrane Bioreactor (MBR) combines biological treatment with membrane filtration. It produces the highest quality recycled water of any biological process.
If you want to turn sewage directly into crystal-clear water suitable for toilet flushing, gardening, or even cooling towers, MBR (Membrane Bioreactor) is the technology of choice.
It replaces the gravity settling (clarifier) of traditional plants with a physical barrier—an Ultrafiltration (UF) Membrane.
How MBR Works
- Biological Tank: Bacteria consume the waste, just like in other processes.
- Membrane Tank: Instead of waiting for the sludge to settle, we stick a suction pipe connected to microscopic membranes (0.04 microns) directly into the sludge soup.
- Suction: A pump sucks water through the membrane.
- The Result: The bacteria, solids, and even viruses are too big to pass. They stay in the tank. Only pure water molecules pass through.
The Technical Specs
To a water engineer, MBR is all about Flux and TMP.
| Parameter | Standard Activated Sludge (ASP) | MBR Technology |
|---|---|---|
| MLSS (Bacterial Conc.) | 2,000 - 3,500 mg/L | 8,000 - 12,000 mg/L |
| Effluent Quality (TSS) | 10 - 20 mg/L | < 1 mg/L (Total) |
| Footprint Area | 100% (Baseline) | 25% - 40% |
| Bacteria Age (SRT) | 10 - 20 days | 30 - 60 days |
| Disinfection? | Required (Chlorine) | Built-in (Membrane) |
Key Metrics
- Flux: The flow rate per unit area of membrane (L/m2/h). Typical flux is 15-25 LMH.
- TMP (Trans-Membrane Pressure): The pressure needed to suck water through the membrane. If TMP rises too high (> 0.4 bar), it's time for a chemical wash.
- Air Scouring: Bubbles are released at the bottom of the membrane to "scrub" the surface physically, preventing gunk from sticking.
Internal vs. External MBR
- Internal (Submerged): The membrane sits inside the biological tank.
- Best for: Large sewage plants; lowest energy cost.
- External (Side-stream): The sludge is pumped to a separate container where the membrane lives.
- Best for: Toxic industrial waste; easier to clean but 10x higher energy use due to massive pumping.
The Maintenance Ritual: CIP
CIP (Clean-In-Place) is mandatory for MBR survival.
- Maintenance Wash: Weekly 30-minute soak in low-strength chlorine.
- Recovery Clean: Bi-annual deep soak in high-strength Citric Acid (to remove scale) and Sodium Hypochlorite (to remove organics).
The Downsides (Cost)
Quality comes at a price.
- High Capital Cost: The membranes are expensive.
- High Energy Cost: Keeping the membranes clean requires blasting air (scouring) continuously, which uses a lot of electricity.
- Fouling: The membranes get clogged with gunk. They require frequent automated chemical cleaning (CIP) with Citric Acid and Chlorine.
Typical Applications
- Commercial Building basements: Where space is extremely expensive.
- Water Reuse Projects: Golf courses, data centers, and industries that need high-quality recycled water.
- Upgrading Plants: Doubling the capacity of an existing plant without building new concrete tanks.
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