Have you ever noticed a slippery, hard-to-clean layer inside your household water tanks, faucet filters, or industrial circulation pipes? This is what we commonly call biofilm. It is not just ordinary dirt-it is a complex ecosystem composed of bacteria, fungi, algae, and other microorganisms, along with their secreted extracellular polymeric substances (EPS).
Composition and Formation Mechanism of Biofilm
The formation of biofilm is a dynamic process:
1.Attachment: Microorganisms in the water initially attach to the surface of pipes or equipment.
2.Growth and Reproduction: The attached microorganisms begin to reproduce rapidly and secrete a viscous extracellular polymeric substance (EPS).
3.Maturation: The EPS acts like "cement," tightly enclosing the microbial cells and forming a robust, multilayered structure. This structure provides perfect protection for the microorganisms inside, allowing them to resist external environmental stresses.
4.Dispersion and Detachment: Once the biofilm matures, some microorganisms detach from the film and re-enter the surrounding environment as planktonic cells. These detached cells can spread to new surfaces, initiating the formation of new biofilms.
Which industrial equipment or water systems are prone to biofilm formation?
Biofilm is a sticky layer composed of microorganisms and their secreted extracellular polymeric substances. It can form on almost any surface that comes into contact with water. The following are types of industrial equipment and water systems that are particularly susceptible to biofilm formation:
Cooling Towers
Cooling towers are among the most common and favorable places for biofilm growth. They provide ideal conditions for its development:
· Abundant nutrients: Cooling water systems capture dust, organic matter, and algal spores from the air, supplying food for microorganisms.
· Optimal temperature: The temperature range of cooling towers is usually between 25°C and 35°C, which is ideal for the growth of many microorganisms.
· Continuous water flow: Although water is circulating, stagnant areas exist in fillers, basins, and pipe corners, allowing biofilm to attach and thrive.
Pipelines and Heat Exchangers
In many industrial water systems, pipelines and heat exchangers are high-risk zones for biofilm.
· Pipelines: Especially in sections with slow flow or dead zones, biofilm easily forms on the inner wall, increasing water resistance and promoting corrosion.
· Heat exchangers: Once biofilm forms on heat exchanger surfaces, it significantly reduces heat transfer efficiency. Since biofilm has poor thermal conductivity, it acts like an "insulating blanket" that hinders heat transfer.
Filtration Systems
Filtration systems, particularly sand filters, activated carbon filters, and membrane filtration systems, are highly prone to biofilm contamination.
· Sand and activated carbon filters: The large surface area of the filter media adsorbs organic matter, providing abundant attachment points and food sources for microorganisms.
· Membrane filtration systems (e.g., reverse osmosis and ultrafiltration): Once biofilm develops on the membrane surface, it clogs the pores, leading to reduced flux and increased operating pressure, severely impacting the system's performance and lifespan.
Why Is Biofilm So Difficult to Remove?
The real challenge of biofilm lies in its unique structure. The thick EPS protective layer makes it difficult for conventional chemical disinfectants (such as chlorine) to penetrate, preventing effective killing of the microorganisms inside. Even if the surface is cleaned, the microbes within may survive and rapidly regrow. This is why simple physical scrubbing or chemical dosing often only addresses the symptoms, not the root cause, and biofilm problems tend to recur.
The Hazards of Biofilm
Biofilm not only affects water quality but can also cause serious damage to water systems:
·Reduced Efficiency: In heat exchangers or cooling towers, biofilm forms an insulating layer that significantly lowers heat transfer efficiency.
·Equipment Corrosion: Microorganisms within biofilm produce acidic substances, accelerating the corrosion of pipes and equipment. This is known as microbiologically influenced corrosion (MIC).
·Disease Transmission: Biofilm can serve as a breeding ground for pathogenic microorganisms, such as Legionella, posing potential health risks.
Understanding the composition and hazards of biofilm is the first step toward finding effective solutions. Long-term suppression and removal require fundamentally disrupting the conditions that allow biofilm to form.
Addressing Biofilm Problems at the Source-Attachment Points-Using a Scale Inhibitor
We know that the first step in biofilm formation is attachment. The conditions that favor microbial attachment include:
· Rough or porous surfaces: Microorganisms attach more easily to uneven or porous surfaces, while smooth surfaces make attachment more difficult.
· Chemical properties: The surface's hydrophilicity/hydrophobicity and charge can affect the initial adsorption of microbes.
·Presence of scale or deposits: Scale provides support and protection for microorganisms, increasing the likelihood of biofilm formation.
Considering the conditions preferred by biofilms, rough pipe or product surfaces with scale deposits provide initial attachment points for microorganisms, accelerating biofilm formation. By installing a DPSE physical scale inhibitor at the source of the whole-house water system, scale deposition in pipes can be suppressed, keeping the pipe walls relatively smooth and reducing opportunities for microbial attachment.
Additionally, the chips in the DPSE scale inhibitor generate a weak electrode reaction during operation, releasing microcurrents. The resulting electric field in the pipe may influence the surface charge of microorganisms, partially interfering with their initial attachment. However, this effect mainly serves to prevent the creation of a favorable environment for biofilm growth, significantly delaying biofilm formation and preventing it from developing into a large, mature layer. It cannot completely stop biofilm formation.
When Biofilm Struggles to Establish Attachment Points-UV Water Disinfection Takes Effect
Biofilm formation relies on the initial attachment of microorganisms to the surfaces of pipes and equipment. Once these attachment points are disrupted or absent, microorganisms find it difficult to grow stably, and the establishment and maturation of biofilm are significantly delayed.
By forming a smooth chelated layer on the pipe wall, a scale inhibitor can effectively cover potential attachment points, making it difficult for microorganisms to find a foothold. The core of biofilm is the extracellular polymeric substances (EPS) secreted by microorganisms, which form a thick gel-like layer. This EPS layer can absorb or scatter ultraviolet light, reducing the intensity of UV reaching microbial cells. However, when biofilm is unable to establish, most bacteria in the water remain in a planktonic state. At this stage, a UV water disinfection system can directly kill microorganisms in the water, cutting off their reproduction at the source. The two work synergistically to create a dual-protection mechanism.
Dual Protection: Say Goodbye to Biofilm Problems
In summary, traditional single treatment methods are often ineffective because they fail to address the two core issues of biofilm formation: attachment points and microbial sources. Combining a scale inhibitor with a UV water disinfection system provides a perfectly complementary solution.
