What is Membrane Bioreactor?

💧 Introduction: Why MBR is the "Game-Changer" in Wastewater Treatment
Global environmental regulations are tightening-for example, the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants (GB18918-2002) now requires stricter effluent quality. Traditional methods like the activated sludge process struggle to meet these standards. 
Enter MBR: a technology designed to bridge the gap. This guide is tailored for water treatment engineers, plant operators, and procurement decision-makers, focused on solving real-world technical and operational challenges.

What Exactly is an MBR?

A Membrane Bioreactor (MBR) combines membrane filtration (microfiltration/ultrafiltration) with biological treatment. Unlike traditional systems, MBRs replace bulky clarifiers with compact membrane modules, directly separating clean water from sludge. At the same time, MBR is also one of the core technologies in sewage treatment systems.
Think of it as a "super sieve + microbial factory": membranes trap solids, while bacteria break down pollutants to produce high-quality effluent.

MBR vs. Traditional Processes

To highlight MBR's edge, here's how it stacks up against the activated sludge process (common in global):

(Source: 2024 China Ministry of Ecology and Environment)

Key Advantages

High Efficiency

MBRs achieve 96-99% COD removal (vs. 85-90% in traditional systems).

Anti-Fouling Design

Hydrophilic PVDF membranes (contact angle <40°) reduce pollutant adhesion.

Space-Saving

A 30,000 m³/day MBR plant saved 30% space vs. its activated sludge predecessor.

Realistic Limitations

Membrane Fouling

60% of 3+ year MBR projects face fouling (needs 3-month/1-month backflushes for municipal/industrial use).

Energy Cost

15-20% higher than traditional systems (≈¥0.1-0.2/m³ with China's ¥0.6/kWh electricity).

Maintenance

Membrane replacement costs ¥800-1,200/m² (domestic vs. imported).

There are two main process configurations of membrane bioreactor (MBR): submerged MBR and external MBR.

Submerged MBR

In this configuration, the membrane system (e.g., membrane modules) is directly immersed in the mixed liquor of the bioreactor. After the wastewater is biologically treated, the liquid is filtered directly through the membrane.

The advantages of this configuration include lower energy consumption and easier maintenance, as the membrane modules are usually inside the reactor and can be cleaned by gas reflux (aeration), thereby reducing membrane fouling.

It is often used for smaller installations and/or difficult-to-treat industrial wastewater.

External MBR

The membrane components of the external MBR are not inside the bioreactor, but the bioreactor and the membrane are separated. The treated mixed liquid is pumped to the external membrane unit for filtration, and then the treated water is returned to the reactor.

The advantages of this configuration are the flexibility of membrane operation and easier maintenance, and the choice of efficient membrane cleaning solutions, but it usually increases the footprint and energy consumption of the entire system.

It is typically used in medium and large installations.

Top Brands: Who Leads in China?

China's MBR market is dominated by both global and homegrown players. Here's a quick snapshot:

(Source: 2025 China Water Treatment Industry Report)

2025 Trends to Watch

Industrial Growth: MBR projects for chemical/pharmaceutical wastewater are up 20% YoY globally.
Smart Tech: AI-powered membrane health monitoring predicts fouling risks.

Membrane Fouling

Signs: Reduced flux (e.g., 3,000 LMH → 2,000 LMH) or rising TMP (>0.05 MPa).
Fix:

Physical: Backflush every 3 months (municipal) or 1 month (industrial).
Chemical: Use 1,000 ppm sodium hypochlorite solution.

Sludge Buildup

Signs: Uneven aeration, poor sludge settling.
Fix:
Optimize aeration (switch to "pulsed aeration" to reduce dead zones).
Control MLSS (8,000-12,000 mg/L via regular sludge discharge).

High Energy Use

Signs: Energy costs >30% of total OPEX.
Fix:
Choose low-energy membranes (e.g., Bishuiyuan's "SuperHydro PVDF" cuts 10% energy).
Use cross-flow filtration to lower membrane velocity needs.

1. Municipal Wastewater Treatment: MBRs are commonly used in municipal wastewater treatment plants to treat domestic sewage. They effectively remove organic matter, nutrients, and pathogens, thus producing high-quality effluent that can be reused for irrigation, industrial processes, or even potable water supply after further treatment.
2. Industrial Wastewater Treatment: MBRs are suitable for treating wastewater from various industries, including food and beverage, pharmaceuticals, textiles, and chemicals. They can handle high organic loads and challenging contaminants, allowing for the treatment of water with high concentrations of pollutants.
3. Landfill Leachate Treatment: Membrane bioreactors are effective for treating landfill leachates, which contain high concentrations of organic and inorganic compounds. MBRs can reduce the pollution load, making the leachate safe for discharge or further treatment.
4. Reclaimed Water Systems: MBR technology is used to produce reclaimed water suitable for non-potable uses, such as irrigation, toilet flushing, and industrial processes. This application is particularly important in areas facing water scarcity.
5. Aquaculture and Fish Farming: MBRs are employed in aquaculture systems to treat wastewater from fish farms. They help maintain water quality by removing excess nutrients and pathogens, thus promoting healthy fish growth and reducing environmental impact.
6. Decentralized Wastewater Treatment: MBRs are ideal for decentralized treatment systems, such as small communities, rural areas, or remote locations where centralized treatment facilities are not feasible. Their compact design and high efficiency make them suitable for onsite wastewater management.
7. Food Processing: In the food industry, MBRs can be used to treat process water and wastewater generated from food processing operations. This application helps in water recycling and meets regulatory discharge requirements.
8. Brewery Wastewater Treatment: MBRs can effectively treat wastewater from breweries, which often contains high levels of organic material from brewing processes. The technology allows for the recovery of valuable components and minimizes environmental impact.
9. Pharmaceutical Wastewater Treatment: Due to the presence of complex organic compounds and pharmaceuticals, MBRs offer a suitable solution for treating wastewater from pharmaceutical manufacturing facilities, ensuring compliance with environmental regulations.
10. Reverse Osmosis Pre-treatment: MBRs are often used as a pre-treatment step for reverse osmosis (RO) systems, providing high-quality water that is essential for the efficient operation of RO membranes by removing suspended solids and organic matter.

How long do MBR membranes last?

A: With regular maintenance (backflushes + chemical cleaning), domestic membranes last 5-8 years; imported ones 8-10 years. Example: A Bishuiyuan membrane installed in 2018 at a Guangdong plant is still operational in 2025.

MBR vs. MBBR-What's the difference?

A: MBR focuses on membrane separation (superior effluent), while MBBR uses biofilm carriers (lower cost). See the quick breakdown:

Is MBR good for small plants?

A: Absolutely! Compact, containerized MBR units (20-50 m² footprint) are ideal for rural areas or small towns.