Optimization of Positional Angle of Propeller–Aspirator Pump Aerator and Its Performance Evaluation at Different Dynamic Condition Avinash Kumar 1*+ , S. Moulick 2 , B.C. Mal 1 , C.K Mukherjee 1 1 Agricultural and Food Engineering Department, IIT Kharagpur 721302, India 2 Kalinga Institute of Industrial Technologies, Bhubaneswar751024, India Abstract. Aeration test was conducted in a brick masonry tank of dimension 5 × 3 × 1.5 m 3 to evaluate the optimum geometric condition of Propeller –aspirator pump aerator, i.e., positional angle of propeller shaft (α).The results indicated a maximum SAE at α = 75°. Keeping the geometric condition constant (α = 75°), aeration experiments were further conducted at different rotational speeds of propeller shaft, N ranging from 1420 to 2840 rpm with an interval of 355 rpm and different values of submergence depth, d from 140 to 460 mm with an interval of 80 mm to evaluate the effect of dynamic conditions on aeration characteristics. Non- dimensional numbers related to standard aeration efficiency (SAE) and wire power (P) termed as E and Ne respectively, were introduced. It was found that E and Ne could be well correlated with Froude number (Fr) and Reynolds number (Re) respectively. Keywords: Aeration, Positional angle, Dimensionless numbers 1. Introduction Dissolved oxygen (DO) is considered to be the most vital water quality parameter in water and wastewater treatment. Atmospheric oxygen gets dissolved in water through diffusion process. As diffusion is a very slow process, aerators are generally used to maintain desired level of DO in water body. The aerators consume around 60% of the total energy consumption in a typical activated sludge wastewater treatment plant [1]. Therefore, the prime idea is to minimize the energy consumption by utilizing properly designed aerators. Presently diffused-air and surface aerators are being popularly used in wastewater treatment plants as well as in lakes and aquacultural ponds. The propeller-aspirator-pump aerator draws atmospheric air through a rotating hollow shaft which is connected to an electric motor at one end and a propeller at the other end which is submerged under water. Basically the propeller accelerates the water to a velocity high enough to cause a drop in pressure over the diffusing surface. This forces air to pass through a diffuser in the hollow shaft and enter into the water as fine bubbles. The fine bubbles thus formed are thoroughly mixed with the water due to the turbulence created by the propeller. The aeration performance of a propeller-aspirator-pump aerator depends on the positional angle of propeller shaft, submergence depth of the shaft, rotational speed of the propeller and the design features of the propeller. Keeping in view the above points, the present investigation was focussed on determining the effect of various geometric and dynamic conditions on aeration efficiency of a propeller- aspirator-pump aerator. 2. Theoretical Considerations + Corresponding author. Tel.: + (91 9734426775); fax: + 91 3222 283136 E-mail address: avinashiitkgp86@gmail.com 155 2012 International Conference on Environment Science and Engieering IPCBEE vol.32(2012) © (2012)IACSIT Press, Singapoore