Oxygen transfer rate

The purpose of the paper is to demonstrate that the use of fine bubbles generators which are moving into the water is more efficient than the use of fixed fine bubbles generators. The results of the theoretical and experimental researches on the oxygen transfer rate to water are presented in the case of an immobile fine bubbles generator. Keywords—Water; aeration; generating air bubbles; fine bubble generators; oxygen transfer rate; I. INTRODUCTION Oxygen transfer to water, which occurs both in aquariums, fish breeders and sewage, is an important problem in applying aeration technologies. If fine bubbles aeration [1] is used, significant energy savings are obtained, 20 ÷ 50% of the energy required for aeration [2]. Of the power consumption of a sewage plant, 67% is the energy consumption of water treatment [1] [2]. Reducing energy consumption can be done by using fine bubbles generators (FBG) where the pressure loss is low; at the same time, the efficiency of the oxygen transfer to water must be higher and the consumption of compressed air should be reduced. Air pressure at the entrance to the fine bubbles generator is a very important parameter in the selection and monitoring of fine bubbles generators, regardless of the shape or material from which they are built. It is necessary to monitor this parameter during the operation of the aeration system as it indicates the operation state of the fine bubbles generator by the fact that any clogging of the FBG orifices automatically leads to an increase in air pressure at the entrance. The size and the orifices dimensions is a major parameter of FBG, because it directly affects the working pressure of it. The working pressure of the FBG is the air pressure under the orifices plate. Using FBG which moves in water, i.e. mobile FBG has the following advantage: the trajectory of the air bubbles in water is a curve directed toward the free surface of the water; as a result the contact time between the air bubble and the water is higher, the rate of increase in the dissolved oxygen concentration in the water will be higher. As a result, the time required to aerate the water is reduced.