In-Depth: 10 Key Questions and Answers About the MBBR Process

How long does it take for the carrier to form a biofilm during low-temperature commissioning?

1.Visible Biofilm Formation: The first part is the time it takes for a visible biofilm to appear on the carrier, which can be observed with the naked eye. This typically takes about seven days.

2.Compliance Time: The second part is the time needed for the system to meet discharge standards, which generally occurs within one month.

3.Mature Biofilm Formation: The third part is the time required for the biofilm to become fully mature, which takes much longer. From a professional perspective, for a biofilm to be considered fully mature, it should go through at least one complete cycle of winter and summer. This allows the microbial community on the biofilm to achieve ultimate stability.

Summary: From an academic standpoint, the biofilm is considered stable after undergoing one winter and summer cycle. From an operational effectiveness perspective, the effluent can meet standards within thirty days. Finally, from a visual standpoint, the biofilm can be observed on the carrier within seven days.

Does the MBBR process require additional addition of microbial agents?

Answer: Strictly speaking, MBBR does not require the addition of microbial agents. It operates by optimizing parameters that allow for natural enrichment of microorganisms, such as nitrifying bacteria or denitrifying bacteria. The conditions of the biofilm in the MBBR are favorable for the attachment of these bacteria. For example, in the case of anammox (anaerobic ammonium oxidation), specific conditions promote the attachment of anammox bacteria.

However, under special water quality conditions—such as wastewater that is difficult to degrade or has a very uniform source—certain specialized microbial agents can have specific effects. In these cases, microbial agents can be added as an initial inoculation, but subsequent additions are generally unnecessary.

In summary, for domestic wastewater, adding microbial agents is not needed. However, for certain specific types of wastewater, it could be considered a research topic to explore the effects of adding microbial agents.

Some industry experts say that fillers are prone to clogging and that fluid dynamics are difficult to control. What do you think?

Answer: This issue is indeed a challenging one. It is precisely because of such challenges that different technical teams and manufacturers can be distinguished in their ability to overcome them. Those who successfully address these issues can achieve world-leading status. If problems arise and cannot be resolved, those teams or manufacturers will gradually be eliminated from the market.

Does MBBR require denitrification backwashing?

Answer: The biggest advantage of MBBR, compared to traditional biofilm systems, is that it does not require backwashing. This is because the biofilm in MBBR naturally detaches on its own. When the biofilm is highly active, it produces more extracellular polymeric substances, which increases its stickiness. As the biofilm ages and the secretion of extracellular substances decreases, its stickiness weakens, causing it to naturally detach during the fluidization process. New biofilm then forms in its place. Therefore, backwashing is not needed in MBBR systems.

What is the core wonder of MBBR?

Answer: The core of MBBR lies in two main aspects: the carriers (media) and the fluidization process. The carriers serve as the medium, and currently, there is no unified research indicating the extent of their impact on performance. However, the shape of the carriers does influence fluidization. Globally, the most commonly used carriers are flat cylindrical shapes. Research on carriers is ongoing, and it’s worth exploring various types to determine which works best.

From an engineering perspective, there are several dimensions to evaluate, such as performance, biofilm formation speed, final stability, lifespan, and abrasion resistance. Therefore, at present, the core focus for suspended carriers remains on the fluidization aspect.

What about the filling rate of the MBBR system?

Answer: The currently verified maximum filling rate is 67%. In practical engineering applications, the highest achievable filling rate is 60% for aerobic zones and 50% for anoxic zones.

Can an MBBR system still operate at a water temperature of 3 degrees Celsius?

Answer: There have been practical cases in the Xinjiang region where MBBR systems have been able to operate stably at water temperatures of around 7 to 8 degrees Celsius. While water temperatures as low as 3 degrees Celsius have not been encountered domestically, according to available information, the Nordheim wastewater treatment plant in Norway (which serves the Winter Olympics) receives inflow from melting ice and snow with a water temperature of 3 degrees Celsius. It has been proven through practice that the MBBR system can operate stably and meet standards at this temperature.

In the first large-scale wastewater treatment plant in China to apply MBBR technology, the Wuxi Lucun Wastewater Treatment Plant, are the aeration system and the propeller system present simultaneously?

Answer: The Wuxi Lucun Wastewater Treatment Plant is the first in China to meet the Class A discharge standard and the first to use a large-scale IFAS/MBBR system. The Lucun plant utilizes a circulating flow tank design, which is similar to the traditional bottom aeration oxidation ditch model. It has both propellers and aeration systems. However, during installation, aeration should not be present near the propellers.

Is there a risk of sludge bulking with the use of carriers?

Answer: The primary cause of sludge bulking is filamentous bacteria. According to reports from abroad, carriers can help reduce sludge bulking because they can break up the "long filamentous" bacteria in the sludge system. For normal sludge flocs, whose size is much smaller than that of the carriers, the carriers do not break up the sludge. Therefore, based on foreign studies, MBBR is beneficial for improving sludge settleability. In our engineering practice, we have not observed any significant sludge bulking issues in systems that use MBBR.

How can one quickly find high-quality MBBR media suppliers?

Answer: You should definitely consider Hangzhou AquaSust Water Technology Co., Ltd.. Founded in 1992, the company covers an area of 42,000 square meters with a building area of over 68,000 square meters and employs more than 300 professional technical personnel. The company is a national high-tech enterprise, fully implementing the ISO 9001, ISO 14001, and ISO 45001 systems. It has a provincial-level enterprise research institute and holds over 130 national patents.

Hangzhou AquaSust specializes in the research and production of environmental water treatment media and hydraulic products. The company is also the drafter of the industry standard HG/T5924-2021 "Biofilm Carrier for Waste (Sewage) Water Treatment."

The company has long-term collaborations with universities such as Hohai University, Zhejiang University, Xi'an Jiaotong University, and Hubei University of Technology. Its products are widely used in various fields, including industrial wastewater, municipal wastewater, rural wastewater, and water for recirculating aquaculture. They are also involved in the research of environmental materials for rivers, seas, lakes, and water management.