Improvement of oxygen transfer efficiency in aerated ponds using liquid-film-assisted approach

Abstract

In aerated ponds, oxygen is generally supplied through either diffused or mechanical aeration means. Surface transfer and bubble transfer both contribute significantly to oxygen transfer in a diffused aeration system. In the present study, a liquid-film-forming apparatus (LFFA) is successfully developed on a laboratory scale to improve considerably the surface transfer via the unique liquid film transfer technique. The experimental results show that the volumetric mass transfer coefficient for LFFA alone is found to be as much as 5.3 times higher than that for water surface and that the total volumetric mass transfer coefficient for the liquid film aeration system increases by 37% in comparison with a conventional aeration system. Additionally, by tuning finely the structural parameters of the LFFA, it can also lead to high dissolved oxygen (DO) water with the DO percent saturation greater than 90%. More importantly, this result is accomplished by simply offering a single-pass aeration at a depth as shallow as 26 cm. As a result, the objective of economical energy consumption in aerated ponds can be realized by lowering the aeration depth without sacrificing the aeration efficiency. It is noteworthy that the data presented in this study are acquired either numerically or experimentally.

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“…Bagatur and Sekerdag (2003) [10] studied the air -entraining rate of circle nozzles with and without air vents, and in particular, the influence of various numbers and placements of the air holes and the distance between air hole sites and the nozzle outlet. Ozkan et al (2006) [11] performed a series of laboratory experiments on tap water for studying the efficiency of air injection using Venturi aerator considering the effects of many parameters such as; the dimensions of Venturi aerator and the pipe at which it is installed, and liquid density and viscosity on air injection rate. [12] investigated the air entrainment properties in a descending water jet setup with rectangular nozzles and rounded ends.…”

Combination of Surface and Diffused Aerators in Term of Oxygen Transfer Efficiency and Energy Performance

“…It was found that all of the installation patterns had the same trend of the conductivity which increased immediately when the NaOH was dosed, after that it was slightly decreased with time, after that the result was calculated in term of the exit age (E(t)) in the function of time as shown in figure 2. 13. Then the trend of E(t) was analyzed in form of average residence time (ART) which it was around 49.4-50.5 min, comparing to 56.3 min of the designed residence time, this result represented the short circuit flow was occurred during the operation period.…”

“…And total volumetric mass transfer coefficient was increased around 37%. By this research the suitable structure of the LFFA was studied and optimized, to propose the suitable shape of the LFFA for oxygen transfer improvement in aeration system [13].…”