Why is it necessary to regularly dose fungicides in circulating water systems?
Publish Time: 2025-09-11
In industrial production and large-scale building operations, circulating water systems, like the human body's blood circulation network, continuously provide temperature control for cooling equipment, heat exchangers, and air conditioning systems. However, this seemingly closed waterway environment is in fact a breeding ground for microbial growth. The combination of suitable water temperature, rich nutrients, fluctuating flow rates, and the constant influx of spores and organic matter from the air creates ideal conditions for the growth of bacteria, fungi, and algae. If left unchecked, microorganisms can rapidly proliferate, forming difficult-to-remove biosludge, which can lead to a series of cascading problems. Therefore, regular dosing of fungicides is not an optional supplementary measure but an essential component to maintaining healthy system operation.Excessive microbial growth primarily impacts heat transfer efficiency. When bacteria attach to the inner walls of pipes and secrete extracellular polymeric substances, they form a slippery biofilm. This film itself has extremely poor thermal conductivity, acting like an insulating blanket covering the heat exchanger tubes, hindering heat exchange. More seriously, biofilms trap suspended particles, corrosion products, and minerals in the water, gradually accumulating into thick biosludge. These deposits not only further reduce heat exchange efficiency but can also clog pipes, filters, and nozzles, resulting in poor water flow, increased pump load, and even localized overheating or equipment downtime.Microbial activity can also exacerbate metal corrosion. Certain sulfate-reducing bacteria metabolize in anoxic environments to produce hydrogen sulfide, which is highly corrosive to carbon steel. Iron-oxidizing bacteria, on the other hand, oxidize ferrous ions to form rust tumors, destroying the passive film on the metal surface and inducing pitting corrosion. These microbial-induced corrosion processes are often hidden and rapidly progress. By the time they are discovered, perforations or leaks have already occurred, leading to costly repairs. Furthermore, corrosion products serve as a substrate for microbial attachment, creating a vicious cycle of "corrosion-growth-re-corrosion," seriously threatening the structural safety of the system.Cooling towers, as the part of the circulating water system most exposed to the outside world, are a source of microbial transmission. A moist, warm fill layer provides an ideal growth environment for algae. Sunlight can cause algae to spread rapidly, reducing ventilation efficiency and potentially entering the system with water flow. Pathogens such as Legionella can also thrive in warm and humid environments. If they are released into the air via aerosols, this poses a public health risk, especially in places like hospitals, hotels, and office buildings.Physical cleaning or filtration alone cannot eradicate these problems. Biofilms offer a strong protective barrier, shielding against regular flushing and allowing microorganisms to continue to thrive. Chemical fungicides penetrate this barrier, killing living microorganisms and removing biosludge, restoring the system to a clean state. Regular dosing of fungicides not only controls the current microbial load but also inhibits regrowth, maintaining stable water quality.Oxidizing and non-oxidizing fungicides each have their own characteristics. The former quickly kills floating bacteria, while the latter excels at penetrating deep into biofilms. A combination of these two is even more effective. Using either a burst or continuous dosing method allows for flexible adjustments based on system operating conditions to ensure microbial growth is always under control.More importantly, good microbial control prolongs the effectiveness of corrosion and scale inhibitors. When biosludge is reduced, the chemicals can effectively reach metal surfaces and inhibit crystal growth, preventing them from becoming ineffective due to coating. This makes the entire water treatment solution more coordinated and efficient.Regular dosing of fungicides is essentially proactive maintenance of system health. It's not a remedial measure to deal with a problem, but a core component of preventive management. When clear water circulates smoothly through clean pipes, heat exchange equipment operates efficiently, and its lifespan is extended, it's all thanks to the silent efforts of fungicides. They safeguard not only water quality but also the stability, safety, and economical operation of the entire system.
