What method is effective in reducing gases like methane and carbon dioxide in water?

Aeration is an effective method for reducing gases like methane and carbon dioxide in water. This process involves introducing air into the water, which creates turbulence and helps to enhance the transfer of gases from the water to the atmosphere. As water is agitated during aeration, dissolved gases can escape, effectively lowering their concentration in the water. This is particularly useful in water treatment processes, where the removal of unwanted gases can improve water quality and reduce potential odors or other issues.

In contrast, filtration primarily focuses on removing particulate matter and certain contaminants but does not significantly address dissolved gases. Chlorination is a method used for disinfection, targeting microorganisms rather than gas removal. Softening is used to remove hardness from water, dealing with issues like calcium and magnesium ions, but does not impact dissolved gases. Thus, aeration stands out as the correct method for reducing methane and carbon dioxide in water.