Generally surface aerators are used in the secondary effluent treatment plant for oxygenation. Typically a surface aerator transfers 0.9 to 1.0 kg oxygen per HP of motor per hour. The design and location of surface aerators create anaerobic pockets in the aeration tanks besides frothing at the surface of effluent which results in very low or no oxygen transfer. The submersible aeration system is extremely useful for aeration due to very high oxygen transfer efficiency as against surface aerators/ diffused air systems. Typically the oxygen transfer efficiency varies between 1.6 to 1.9 Kg/HP/Hr. The other advantages are no foundation, no noise, no sprays, low maintenance, thorough mixing, flexibility in layout & space saving.