Aerobic treatment of waste water requires the continuous replenishment of oxygen economically in sufficient quantities. Efficient aerators are developed towards this end. Plunging Hollow Jet Aerators consist of a cone, which deflects the water at the end of a discharging pipe through the annular opening, forming a hollow jet. The thin jet striking the water in the aeration tank formed a circular wave front creating high turbulence and entraining large quantities of air. The efficiency of the device was high (1.5 to 2,25 kg./ kW.h) under standard conditions, for the small opening between the pipe and the cone. But this method can be used only when the water does not have solids which may clog the openings.
Venturi and Sudden Expansion type Aerators
Wastewater from the aeration tank is drawn by a pump and discharges towards the bottom of the tank after passing through an air aspirating device. It could be a Venturi or sudden expansion downstream of which air is admitted. Experiments have shown that such devices can have high oxygenation efficiencies of 1.5 to 2.25 kg /.kW.h under standard conditions. These devices can be used without fear of clogging due to solids in the wastewater. The performance in model is shown in Photograph attached. The devices can be used very efficiently even in small package wastewater treatment plants. The sudden expansion air aspirating aerators are being used in a new waste water treatment plant in the Ettimadai campus.