Most of the time, the old saying, “An ounce of prevention is worth a pound of cure,” is true. Preventing an unwanted event is usually easier than doing remediation work to repair whatever damage is done if the event occurs. However, in virtually all water systems, including pharmaceutical water systems, it is safe to assume that BOTH prevention and remediation are needed to control bacteria and other contaminants.
For pharmaceutical water systems, prevention means not allowing bacteria to enter a system. Tank vent filters are an important part of the prevention process. The system schematic below shows three tanks. Not all of the tanks are required, depending on system design, but at least one tank is in almost all systems.
Tank Vent Filters
Vent filters prevent bacteria and other contaminants found in the air or process gas (like nitrogen) from coming directly in contact with water in storage tanks.
As a tank is filled, the air inside must be allowed to escape. Conversely, as the tank is emptied, the air or gas must be allowed to enter the tank to replace lost liquid volume.
The air or gas entering the tank must have particles and bacteria removed or the water will become contaminated.
The tank filter media must remain dry so that air/gas can pass freely through it. If the filter pores are filled with water, then airflow is blocked, and a vacuum will develop inside a tank being emptied. (Many tanks, like thin aluminum soft drink cans, are built to remain stable when pressurized, but easily crush if even a small vacuum develops.) Hydrophobic membrane such as PTFE is typically used because it resists wetting from water vapor and reduces the risk of tank failure.
It is important to remember that each facility and water system design is different. The nature of the particles in the environment can significantly change the filter system design required and the number of filters used.