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ABSTRACT
Aeration experiments were conducted in a brick masonry tank of dimension 4 m × 4 m × 1.5 m to study the engineering and economic analysis of pooled circular stepped cascade (PCSC) aeration system. Based on dimensional analysis, non-dimensional numbers related to geometric, dynamic and process parameters were proposed. The non-dimensional geometric parameters - percentage coverage of circumference of each step by enclosure (Pe) and number of enclosures in each step (Ne) were optimized by conducting aeration experiments at varied levels and keeping the dynamic conditions constant (pump discharge, Q = 0.016 m3/s). Maintaining the optimized geometric conditions (Pe = 20% and Ne = 9), aeration experiments were further conducted at different values of Qto develop simulation equations for prediction of aeration characteristics of PCSC aeration system at different dynamic conditions. Simulation equations for oxygen transfer and power consumption based on Froude (Fr) criterion were developed subject to 0.0014 Fr 0.0144. Standard aeration efficiency of the developed prototype PCSC aerators based on estimated brake power ranged between 2.43 to 3.23 kg O2/kW·h. The economic comparison of newly developed PCSC aerator in terms of aeration cost (`/h) with other four different types of aerators - circular stepped cascade (CSC), 1-hp paddle wheel (PW1), 2-hp paddle wheel (PW2) and propeller aspirator pump (PAP) was performed. Aeration costs for different types of aerators at different pond sizes, different initial DO concentrations of pond and operating hours of aerators were estimated; assuming a typical Indian major carp (IMC) culture with commonly practiced stocking density and feeding.
PCSC aerators were found to be suitable for pond sizes with less than 1000 m3 volume of water. However, for pond sizes more than 5000 m3, PW1 and PW2 were found to be more economical.
Keywords: Aeration, aeration cost, aerator selection, economic comparison, pooled circular stepped cascade, standard aeration efficiency.
