You can use a deaerator which is defined as a piece of equipment which heats water with steam to insure essentially the complete removal of dissolved gases. There are several types of deaerators available, each having its own advantages and disadvantages. 

Internal treatment for dissolved oxygen corrosion is normally accomplished by the addition of sodium sulfite. Most oxygen scavengers contain a catalyst which speeds the reaction of the sulfite with the oxygen. In systems equipped with a deaerator the sulfite should be fed to the storage tank of the deaerator or to either the suction or pressure side of the feed water system, including the condensate tank. Internal treatment for carbon dioxide is normally accomplished by the use of volatile amine. “Amine” refers to any number of chemicals derived from ammonia. There are two major groups of amines in practice as water treatment chemicals today. They are normally referred to as “neutralizing amines” or filming amines” depending upon whether they neutralize the acid formed by carbon dioxide or forms a protective film on the metal. Filming amines do not neutralize the carbonic acid which forms in condensate systems. Instead, they form a film on the metal which is non-wettable, or impervious to water. This protective film prevents the corrosive impurities from contacting the metal. Neutralizing amines function by increasing the PH of the condensate. Normally, they are fed at such a rate that the PH of the condensate is maintained slightly above 7.0. Satisfactory reduction of carbon dioxide corrosion is possible with the use of a neutralizing amine. It is necessary to supplement this type of condensate protection with an oxygen scavenger to remove dissolved oxygen. Whether condensate corrosion is controlled by chemical treatment or a combination of mechanical and chemical methods, it is important that careful checks and testing be incorporated as a part of the treatment program. No treatment can be better than the way in which it is applied. Consult a water treatment expert to get you started on the right foot.