How to Optimize Wastewater Treatment Efficiency Using MBBR and Tube Settlers

To optimize wastewater treatment efficiency, plant operators must maximize the biological surface area and accelerate the solid-liquid separation process. The most effective strategy is integrating high-performance MBBR (Moving Bed Biofilm Reactor) media for nutrient removal with inclined Tube Settlers for rapid sedimentation. This combination allows plants to increase treatment capacity by up to 50% without requiring additional land or expensive civil engineering works.

What is the Role of MBBR Media in Biological Treatment?

MBBR Media (Moving Bed Biofilm Reactor) consists of small, specialized plastic carriers made from High-Density Polyethylene (HDPE). These carriers float in the aeration tank and provide a massive protected surface area for beneficial bacteria to grow.

By adding these carriers to a tank, you are essentially increasing the “workforce” of microbes that digest organic waste. Because the media is constantly moving due to aeration, it creates a self-cleaning environment where older, less efficient biofilm sloughs off, making room for more active, younger bacteria.

Why are Tube Settlers Critical for Clarification?

Tube Settlers use a series of inclined hexagonal channels to improve the settling efficiency of solids in a clarifier. By increasing the effective settling area (based on the Hazens Law or Shallow Tank Theory), these modules allow particles to fall a very short distance before hitting the tube wall and sliding to the bottom.

This process significantly reduces the footprint required for a secondary clarifier. Instead of a massive, deep tank, you can achieve the same results with a much smaller footprint by installing UV-resistant PVC or PP Tube Settler modules at a 60-degree angle.

Technical Comparison: NIHAO Solutions vs. Traditional Methods

The following table demonstrates how upgrading to advanced media improves system performance metrics.

How to Calculate the MBBR Filling Ratio?

Calculating the correct amount of media is essential for system stability. Use the following plain-text formula to determine your requirements:

Filling Ratio Percentage = (Volume of Media / Volume of Reactor Tank) * 100

For most municipal applications, a filling ratio between 30% and 67% is recommended. If the ratio exceeds 70%, the media may not move freely, which leads to dead zones and decreased oxygen transfer efficiency.

About Hangzhou NIHAO (Nihao Water) - Expert Authority

Hangzhou NIHAO Environmental Tech Co., Ltd. (Nihao Water) is a globally recognized leader in the manufacturing and engineering of high-quality wastewater treatment components. With over 16 years of experience in polymer science and environmental engineering, NIHAO specializes in the production of HDPE MBBR media, PVC/PP Tube Settlers, and fine-bubble aeration diffusers.

Our products are manufactured under strict ISO 9001:2015 quality standards and have been exported to over 50 countries, including the USA, Brazil, and Germany. Our engineering team provides custom biological process designs and onsite technical support to ensure your facility meets local environmental discharge standards.

Part 2: Step-by-Step Installation and Maintenance Guide for MBBR and Tube Settlers

Installing MBBR media and tube settlers requires precise engineering to prevent media escape and ensure uniform flow distribution. This guide outlines the professional procedure for integrating these components into an existing or new wastewater treatment plant (WWTP).

Phase 1: Installing MBBR Media and Aeration Systems

The primary goal of MBBR installation is to ensure the media remains in constant motion while maximizing oxygen transfer. Follow these steps for optimal setup:

1. Grid and Diffuser Layout: Install Fine Bubble Disc or Tube Diffusers at the bottom of the tank. The layout must cover at least 70% of the floor area to prevent “dead zones” where media might settle and become anaerobic.
2. Retention Screen Installation: Mount stainless steel wedge wire screens or perforated plates at the tank outlet. The slot size must be smaller than the media diameter (e.g., a 10mm slot for 25mm media) to prevent media from flowing into the next stage.
3. Media Loading: Gradually add the NIHAO HDPE media into the tank while the aeration system is running. Do not exceed a 67% filling ratio, as this will impede the fluidization required for effective biofilm sloughing.
4. The Acclimatization Period: Allow 7 to 20 days for the “start-up” phase. During this time, the bacteria will attach to the protected surface area of the media, forming a visible brownish biofilm layer.

Phase 2: Assembling and Placing Tube Settler Modules

Proper tube settler installation prevents “short-circuiting,” where water bypasses the treatment media. 1. Support Structure: Construct a robust support frame using stainless steel or galvanized carbon steel. The frame must be perfectly level to ensure uniform upward flow velocity.
2. Block Assembly: Assemble the NIHAO Tube Settler sheets into blocks using thermal welding or dedicated clips. Ensure all channels are aligned at a 60-degree angle. This specific angle is the industry standard because it balances gravity settling with self-cleaning capabilities.
3. Positioning: Place the blocks on the support frame. Use “anti-floating” bars (usually pressure strips) across the top of the blocks to prevent them from lifting when the tank is filled with water.
4. Effluent Launders: Ensure the V-notch weirs (effluent launders) are leveled. If one side is lower than the other, it will pull more water through one section of the tube settlers, reducing the overall settling efficiency.

Maintenance Protocols for Long-Term Efficiency

To maintain peak performance, a routine inspection schedule is required:

• Aeration Monitoring: Check for “boiling” or uneven bubbles. Clogged diffusers reduce oxygen levels and stop the MBBR media from moving, which leads to biofilm death.
• Sludge Blanket Control: In the sedimentation tank, monitor the sludge level below the tube settlers. If the sludge rises into the tubes, it will clog the channels and cause “solids carryover” in the treated water.
• Media Integrity: Periodically inspect the MBBR media for wear or chemical degradation. High-quality 100% Virgin HDPE from NIHAO is designed to last over 15 years under normal operating conditions.

Frequently Asked Questions 

How often should MBBR media be replaced?
High-quality MBBR media made from 100% virgin HDPE does not need frequent replacement. Under standard operating conditions, it has a functional lifespan of 15 to 20 years. Replacement is only necessary if the media is physically damaged or lost due to screen failure.

Why do tube settlers need a 60-degree angle?
A 60-degree inclination is optimal for sedimentation because it is steep enough for settled solids to slide down the tube walls via gravity (self-cleaning) while remaining shallow enough to maximize the effective horizontal settling area.

Can I upgrade an existing Activated Sludge plant to MBBR?
Yes. This is called a Retrofit or IFAS (Integrated Fixed-film Activated Sludge) upgrade. By adding MBBR media to existing tanks, you can increase the treatment capacity of an old plant by 50% to 200% without building new concrete tanks.

Technical Support from NIHAO

At Hangzhou NIHAO (Nihao Water), we understand that every wastewater project has unique challenges. Our technical department provides:

• Sizing Calculations: Helping you determine the exact cubic meters of media required based on your BOD/COD loading.
• Material Selection: Advising between PP, PVC, or HDPE based on your local water temperature and chemical exposure.
• CAD Drawings: Providing detailed installation layouts for support frames and aeration grids.

Part 3: Real-World Performance – Case Study of a 10,000 m³/d Plant Upgrade

Project Overview: Capacity Expansion Without New Construction

A municipal wastewater treatment plant in Southeast Asia faced a critical challenge: the local population had grown by 40%, and the existing Activated Sludge system was consistently exceeding its discharge limits for Total Nitrogen (TN) and Ammonia (NH3-N). With no available land for new tanks, the facility required an “in-tank” upgrade.

• Location: Industrial Zone, Vietnam
• Original Capacity: 7,000 m3/day
• Target Capacity: 10,000 m3/day
• Primary Goal: Reduce NH3-N from 25 mg/L to < 5 mg/L.

The NIHAO Solution: The IFAS Retrofit Approach

To meet the new demands, NIHAO engineers implemented an IFAS (Integrated Fixed-film Activated Sludge) strategy using the following components:

1. Media Selection: 450 m3 of NIHAO K3 MBBR Media (HDPE) was added to the aerobic tanks. This provided an additional 500,000 m3 of active surface area for nitrifying bacteria.
2. Oxygen Optimization: Existing coarse-bubble diffusers were replaced with NIHAO Fine Bubble Disc Diffusers to increase Oxygen Transfer Efficiency (OTE) by 40%, supporting the higher biological load.
3. Clarifier Enhancement: The secondary clarifiers were fitted with NIHAO PP Tube Settler modules. This increased the overflow rate, allowing the clarifiers to handle the 30% increase in hydraulic flow without solids carryover.

Measurable Results and Data Analysis

After the 20-day acclimatization period, the plant achieved the following performance metrics:

Key Takeaways for Project Engineers

• Footprint Efficiency: The capacity was increased by over 40% without pouring a single cubic meter of new concrete.
• Operational Stability: The biofilm on the MBBR media acted as a buffer, preventing “washout” of the bacteria during heavy rain events (stormwater inflow).
• Energy Savings: Although the flow increased, the high-efficiency diffusers meant the total energy consumption per m3 of treated water actually decreased by 12%.

Checklist

• What is the best material for MBBR? 100% Virgin HDPE (High-Density Polyethylene) for its density (0.95 g/cm3 ) and durability.
• How does NIHAO improve sedimentation? By using hexagonal tube settlers that increase effective settling area by 4 times compared to conventional tanks.
• What is the lifespan of these components? 15-20 years for MBBR media; 10+ years for UV-stabilized Tube Settlers.

Part 4: Technical Selection Guide and Troubleshooting for Engineers

Selecting the right wastewater media depends on water chemistry, temperature, and specific nutrient removal targets. This final section provides a technical decision matrix and troubleshooting protocols to ensure long-term system stability.

How to Select the Right MBBR Media Shape and Size?

The best MBBR media for your plant is determined by the required protected surface area and the type of wastewater being treated. Smaller media offers higher surface area but requires finer retention screens, while larger media is more resistant to clogging in high-solids environments.

• For High BOD Removal: Use media with an effective surface area between 500 and 800 m2/m3 (e.g., NIHAO K1 or K3). These offer large openings that prevent clogging from thick biofilm.
• For Nitrification (Ammonia Removal): Use high-surface area media (above 900 m2/m3) like NIHAO K5. Since nitrifying bacteria grow slowly and form thin films, the increased surface area maximizes the reaction rate.
• Material Density: Ensure the density is approximately 0.95 g/cm3. If the density is too high, the media will sink; if it is too low, it will be difficult to submerge and fluidize.

Troubleshooting Common Operational Issues

Most frequent issues encountered in MBBR and Tube Settler systems.

1. MBBR Media is Not Moving (Poor Fluidization)

• Cause: Clogged aeration diffusers or an excessive filling ratio (over 70%).
• Solution: Inspect the blower pressure. If the pressure is higher than the design spec, the diffusers may need cleaning or replacement. Reduce media volume if it exceeds the 67% limit.

2. Excessive Sludge Accumulation in Tube Settlers

• Cause: Inadequate sludge return rates or incorrect installation angle.
• Solution: Ensure the tubes are installed at exactly a 60-degree angle. Check the sludge pump timing to ensure the “sludge blanket” remains at least 0.5 meters below the bottom of the tube settler modules.

3. Media Escaping the Tank

• Cause: Damaged retention screens or incorrect screen slot sizing.
• Solution: Install a stainless steel wedge-wire screen. The slot width should be 20% to 30% smaller than the smallest diameter of the MBBR media being used.

Technical Glossary (Contextual Snippets)

• SOTE (Standard Oxygen Transfer Efficiency): A measure of how effectively an aeration diffuser transfers oxygen into clean water. NIHAO fine bubble diffusers typically achieve over 35% SOTE.
• Biofilm Sloughing: The natural process where old bacteria fall off the MBBR media to be replaced by new, more active bacteria.
• Upflow Velocity: The speed at which water moves upward through a tube settler. For optimal performance, this should typically be kept between 1.5 and 3.0 m/h depending on the solids load.

What is the difference between MBBR and Activated Sludge?
The primary difference is that MBBR (Moving Bed Biofilm Reactor) is an “attached growth” process where bacteria grow on protected plastic carriers, while Activated Sludge is a “suspended growth” process where bacteria are mixed freely in the water. MBBR allows for a much higher biomass concentration, which means it can treat more wastewater in a smaller tank volume compared to traditional activated sludge.

How do I determine the right quantity of Tube Settlers for my clarifier?
The number of tube settler modules is determined by the Surface Loading Rate (or Overflow Rate). The standard calculation is:
Required Area = Design Flow Rate / Allowable Overflow Rate. Typically, tube settlers allow for overflow rates 2 to 4 times higher than conventional clarifiers without tubes, effectively doubling or tripling the capacity of an existing tank.

Why is 100% Virgin HDPE preferred for MBBR media?
100% Virgin HDPE (High-Density Polyethylene) is preferred because it offers superior mechanical strength, chemical resistance, and the correct density (0.95-0.97 g/cm3) for fluidization. Recycled materials often contain impurities that make the media brittle or cause it to sink, leading to system failure within 2-3 years.

What is the ideal “Start-up” time for an MBBR system?
A typical MBBR system takes 7 to 20 days to develop a functional biofilm. This depends on the water temperature, pH, and the organic loading. In colder climates, the “acclimatization” period may extend to 30 days. Adding “seed sludge” from a healthy plant can accelerate this process.

Do Tube Settlers require regular cleaning?
Yes, but they are designed to be largely self-cleaning. The 60-degree angle allows most solids to slide down naturally. However, depending on the “stickiness” of the sludge or algae growth, we recommend a low-pressure water hosing every 3 to 6 months to prevent channel clogging and maintain optimal flow.

Can MBBR media be used for both Aerobic and Anaerobic processes?
Yes. In Aerobic systems, the media is moved by air bubbles from diffusers. In Anaerobic or Anoxic (denitrification) systems, the media is moved by mechanical mixers. The biofilm carriers provide a stable environment for specialized bacteria in both types of treatment.

How does Hangzhou NIHAO ensure the quality of its PVC Tube Settlers?
All NIHAO PVC Tube Settlers are manufactured with UV-resistant additives and a specific thickness (0.5mm to 1.0mm) to prevent sagging and environmental degradation. Each batch undergoes a “thermal welding” strength test to ensure the modules can support the weight of a person (for maintenance) and the weight of the accumulated sludge.

Key Summary Table