The basic purpose of aeration is the reduction of the content of substances which cause unpleasant tastes and odours as well as discoloration. Aeration is frequently used for treatment of groundwater where it also has additional positive side effects (precipitation of iron and manganese). When treating surface water aeration is useful in adding oxygen to the raw water. Aeration always precedes some other treatment process. The combination of treatment components is determined by the desired result of the treatment.
Aeration equipment is used to intensively mix air and water so as to facilitate the transfer of gases into or out of the water. The following effects can be obtained:
– Addition of oxygen; this may be necessary for surface water where the natural oxygen content was depleted due to the presence of large amounts of organic substances. Aeration contributes positively to subsequent biological treatment (e.g. slow sand filtration).
– Removal of dissolved iron and manganese; iron and manganese are oxidized and form nearly insoluble hydroxide sludge. They can be removed in a settling tank or by means of a coarse filter.
– Removal of excess carbon dioxide (CO2) to prevent corrosion of metal and concrete surfaces.
– Reduction of H2S, CH4 and other volatile compounds which produce objectionable taste and-odour.
– Temperature reduction.
