DESIGN CRITERIA OF AERATED LAGOON

1. Detention Time
   The basis of design Of aerated lagoon can be hydraulic retention time (HRT) as well as the mean cell residence time or solids retention time (SRT). Typical design value of HRT as well as SRT (0c), for suspended growth aerated lagoon varies from about 3 to 6 days, while for facultative aerated lagoon the HRT and SRT varies from 4 – 10 days.
2. Oxygen Requirement
   The oxygen requirement for oxidizing the organic solids, is varying from 0.7 to 1.4 kg of oxygen per kg of BOD5 removed. The oxygenation capacity of aerators is reported to range from 1.85 to 2.0 kg oxygen/ kWh of power delivered at shaft under standard conditions. The oxygenation capacity of aerator at field condition is obtained by using the equation.
3. Power Requirement
   The facultative aerated lagoons should be mixed with an energy level of about 0.8 – 1 W/m3 of basin volume (1kW/103 m3). The threshold energy input for the suspension of bio solids is about 1.5 to 1.75 kW/103 m3. The energy requirement to maintain all of the solids in suspension is 5 to 8 kW/ 103 m3. Aerators ranging from 2 to 50 kW are now readily available
4. Typical Design Criteria