In treating water for the production of pharmaceuticals, the concentration of gases dissolved in the water plays an important role. In many cases the CO2 content in the raw water has to be further reduced to obtain purified water with a conductivity of < 1.3 μS/cm (at a temperature of 25°C).
membrane degasification system downstream of the RO system and before an EDI system. See the flow diagram on page 2. A Polypropylene Hollow Fiber membrane is used to put a gas and liquid phase in direct contact with each other. Because the fiber is hydrophobic, the liquid will not penetrate the pore. A strip gas or vacuum used on the inside of the hollow fiber lowers the partial pressure of the gas phase which causes the gases to diffuse from the liquid phase through the membrane wall into the gas phase. The removed CO2 is continuously swept out of the contactor by the air sweep.
Hollow fiber membrane contactors maximize the surface contact area for efficient, chemical-free, CO2 removal. Historically, NaOH dosing has been used to control CO2. With chemical dosing CO2 is converted into a carbonate, which can be removed by the RO. The latest state of the art technology for this task is membrane degasification
where chemicals are not needed.