Biofilms: A Complex Role in Water Treatment

Biofilm formation process

The formation of biofilm is a complex process, which can be generally divided into the following stages:

Initial adhesion: Microorganisms reversibly adsorb to solid surfaces through their surface attachments (such as flagella, pili, capsules, etc.).
Irreversible attachment: Microorganisms secrete extracellular polymers (EPS) to firmly fix themselves on the surface to form microcolonies.
Maturation: Microcolonies continue to grow to form a three-dimensional biofilm with water channels formed inside to ensure the exchange of nutrients and metabolites.
Dispersion: Under adverse environmental conditions, some microorganisms break away from the biofilm and enter a new environment.

The positive role of biofilm in water treatment

The core technology of sewage treatment: Biofilm method is one of the widely used technologies in sewage treatment. By cultivating biofilm on a specific carrier, the microorganisms in it can effectively degrade organic matter, ammonia nitrogen and other pollutants in sewage, thereby achieving the purpose of purifying water quality. Common biofilm methods include biofilter, biorotating disc, moving bed biofilm reactor (MBBR), etc.
Sludge treatment: Biofilm technology can be used for stabilization and reduction of sludge. By cultivating specific microorganisms in sludge, the degradation of organic matter can be accelerated and the amount of sludge produced can be reduced.
Water purification: Biofilm can effectively remove heavy metals, organic pollutants, pathogens, etc. from water.
Nutrient cycle: Microorganisms in biofilm participate in the nutrient cycle in water bodies and maintain the ecological balance of water bodies.

Negative effects of biofilm in water treatment

Biological fouling: Biofilm grows on the surface of pipes and equipment, which will cause pipe blockage, reduce equipment efficiency, and even cause system failure.
Secondary pollution: The growth of biofilms may lead to the breeding of pathogens and increase the risk of secondary pollution of water bodies.
Impact on water quality: Excessive growth of biofilms may release odorous substances and affect water quality.

How to control the impact of biofilms in water treatment

Optimize process parameters: Control the growth rate of biofilms by adjusting process parameters such as aeration volume and hydraulic retention time.
Select suitable fillers: Select fillers with large surface area and high specific surface area, which are conducive to the growth and shedding of biofilms.
Regular cleaning: Clean the equipment regularly to remove biofilms and prevent pipe blockage.
Add bio-inhibitors: In some cases, bio-inhibitors can be added to control the growth of biofilms.
Adopt new biofilm technology: Develop new biofilm carrier materials and biofilm reactors to improve the stability and treatment efficiency of biofilms.

Future development of biofilm and water treatment technology

Intelligentization of biofilm technology: Real-time monitoring and control of biofilms are achieved through technologies such as sensors, big data and artificial intelligence.
Innovation of biofilm materials: Develop new biofilm carrier materials to improve the impact load resistance and toxicity resistance of biofilms.
Coupling of biofilm with other technologies: Coupling biofilm technology with other water treatment technologies (such as membrane separation, advanced oxidation, etc.) can achieve a higher level of water purification.