When not enough dissolved oxygen is present, at least some of the bio mass will die, and the organic wastes will not be properly treated. If this happens, the plant may have to replace the bugs which, in most cases, proves to be very expensive and time consuming. When too much dissolved oxygen is present, the treatment plant is over aerating, and consequently, wasting costly energy. The equalization basin provides a means of controlling the loading of the treatment process due to varying plant loads caused by erratic industrial discharges, storm water, diurnal variations, etc. It is important to monitor the dissolved oxygen content in the equalization basin stage to ensure that the incoming waste is not excessively loading the treatment plant.
Aeration ensures that proper sludge quality and bio mass growth conditions exist.
The dissolved oxygen added in the aeration basin, through the aeration process, provides the primary life sustaining element for the activated sludge microbes. Most wastewater treatment plants have sludge handling facilities that use an aerobic or anaerobic biological process to treat the sludge, rendering it harmless. When using an aerobic digester the operator wants to ensure the presence of oxygen, similar to monitoring in the aeration basin. When using an anaerobic digester the operator wants to ensure the presence of nitrogen, which is directly correlated to the lack of oxygen. When plant effluent is discharged into a lake or river, its dissolved oxygen level must be maintained to sustain the aquatic life near the discharge point.