Water has a greater affinity for O2 than CO2 so aeration is a cheep and easy way to get the CO2 out of water supplies. It is used often when iron and or manganese are a problem and being held in solution by CO2. The ionic state is altered, becomes less soluble and can be settled out. Council water supplies are usually not high in CO2 as this makes the water acid, corrosive to copper and causing dezincafication of brass fittings like taps.