As suggested, the basic purpose of aeration is the improvement of the physical and chemical characteristics of waters for public supply. Primarily, this improvement involves the reduction of objectional tastes and odors, but some additional benefits of aeration, as a preliminary step to other purification processes have also been noted.
In the cool stagnant bottoms of lakes and reservoirs during late summer and late winter, in deep wells and in the dry-weather flow of some sluggish rivers are found natural waters which are so deficient in oxygen that they are objectional in both taste and odor. Aeration of such waters inproves their taste by supplying the deficient oxygen, rescuing the free carbon dioxide and eliminating much of the hydrogen sulfide and other odorous constitutents present. Removal of iron and manganese from such oxygen deficient waters also usually requires aeration as an intiial step. This initial step allows for the lower oxides of these minerals that are dissolved in the water and combined with carbon dioxide to be converted to higher insoluble oxides and in turn removed by subsequent sedimentation, contact or filtration.