The "Invisible Hero" in Sewage Treatment - Biological Filler

Have you ever wondered how sewage treatment plants turn turbid sewage into clean water? In addition to the contributions of microorganisms, there is also a material that silently contributes - biological filler. It is like an "ecological apartment" in the water, providing a habitat for microorganisms and doubling the efficiency of sewage purification. Today, let's take a look at this "invisible hero"!

I. What is biological filler?

Definition: Biofiller is the core carrier material in the biofilm wastewater treatment process, usually a porous, high-surface-area solid substance. It can adsorb microorganisms to form biofilms and remove pollutants through biodegradation and physical adsorption.
Core functions:
Provide a place for microorganisms to attach and increase the biomass per unit volume.
Prolong the residence time of microorganisms and improve the removal efficiency of complex pollutants (such as ammonia nitrogen and organic matter).

Fig.1 Biological filler biofilm formation process

II. Characteristics of biological fillers

1. Hydraulic performance optimization design
The fluid mechanics properties of biological fillers are mainly reflected in four dimensions: specific surface area, pore structure, geometric morphology and packing density. High specific surface area is the basic condition for maintaining high biomass concentration in the reactor, and the biomass level directly determines the pollutant degradation efficiency of the system. However, the increase in specific surface area will simultaneously increase fluid resistance, resulting in an increase in aeration energy consumption.

The size of the porosity directly affects the effective volume utilization of the reactor. A higher porosity can extend the actual residence time of wastewater, reduce flow resistance, reduce the risk of blockage and short-flow, and reduce the amount of biological filler and infrastructure costs.

2. Chemical stability requirements
The biofiller must be corrosion-resistant and able to withstand the erosion of wastewater components and microbial metabolites. The material itself should be inert to avoid dissolution of harmful substances causing secondary pollution, and must not contain chemicals that inhibit microbial activity. The physical level must meet mechanical strength requirements while maintaining lightweight properties to reduce system load.

3. Mechanisms promoting biofilm attachment
The efficiency of biofilm formation depends on the physicochemical properties of the biofiller:

Physical properties: Surface roughness and microporous structure are key factors. Rough surfaces can accelerate the biofilm formation process, while microporous structures enhance microbial retention through capillary action.

Chemical properties: Surface charge characteristics and hydrophilic and hydrophobic properties play a leading role. The surface of bacteria is usually negatively charged, and the positive potential on the surface of the biofiller can promote cell attachment through electrostatic adsorption. Hydrophilic surfaces can significantly shorten the biofilm formation cycle.

4. Material mechanical properties
A balance needs to be struck between lightness and high strength. The ideal biofiller should have sufficient compressive strength to resist water flow impact, while maintaining a low density to reduce system energy consumption.

5. Economic considerations
The cost of biofillers usually accounts for 30%-40% of the total investment in the biofilm process, so it is crucial to choose cost-effective materials. Raw materials with a wide range of sources and convenient processing should be preferred to achieve cost optimization while ensuring performance.

III. The “Best Partner” Technology of Biofillers

1. MBBR (Moving Bed Biofilm Reactor)
Features: The biological filler flows freely in the pool, and no backwashing is required.
Applicable: High-concentration sewage, upgrade of old sewage treatment plants.

Fig2. Practical application of MBBR process biological filler

2. Biological contact oxidation pond
Features: Biological fillers are fixed in the pond and need to be cleaned regularly.
Applicable: domestic sewage, low-concentration industrial wastewater.

Fig.3 Practical application of biological fillers in biological contact oxidation process

IV. Summary: Choose the right biological filler to make sewage treatment more efficient

Biological filler is the "ecological cornerstone" of sewage treatment. Choosing the right material and process can greatly improve the treatment effect. In the future, with the upgrading of environmental protection requirements, new biological fillers such as graphene and zeolite will become a research hotspot.

The technical value of biological fillers is not only reflected in water purification itself, but also through the coupling of material innovation and process, it promotes sewage treatment towards low-carbon and resource-based development, and becomes an indispensable technical support in the modern water environment governance system.