Estimation of the volumetric oxygen tranfer coefficient (KLa) from the gas balance and using a neural network technique

Abstract

This paper reports on the use of the gas balance and dynamic methods to obtain an estimate of the volumetric oxygen transfer coefficient (kLa) in a conventional reactor during the growth phase of the microorganism Cephalosporium acremonium. A new way of calculating kLa by the dynamic method employing an electrode with a slow response, is proposed. The calculated values of kLa were used in the training of a feedforward neural network, for which the inputs were the parameter measurements of the related variables. The neural network technique proved effective, predicting values of kLa accurately from input data not used during the training phase. In contrast, the gas balance method was shown to be less useful. This could be attributed to the poor data obtained with the apparatus used to measure the oxygen in the exhaust gas, explained by the low rate of oxygen consumption by the microorganism

Optimization of Hydrogenotrophic Denitrification Behavior Using Continuous and Intermittent Hydrogen Gas Supply

“…The hydrogen effectiveness decreased when the hydrogen flow rate was increased, with measurements of 205 mg-N/g-H 2 at 1 mL/min, 199 mg-N/g-H 2 at 5 mL/min, 108 mg-N/g-H 2 at 10 mL/min, and 76.2 mg-N/g-H 2 at 15 mL/ min. This is because the air stone diffuser causes low transfer rate of hydrogen into the liquid phase [14,15]. Therefore, a high volume of hydrogen was required to achieve saturated DH concentrations; meanwhile, a large volume of hydrogen was released into the air during operation.…”

Microbubble Application to Enhance Hydrogenotrophic Denitrification for Groundwater Treatment

“…The increasing rate of DH concentration in the microbubble reactor was found to be faster than that in the millibubble reactor because of the transfer of most microbubbles to the surrounding liquid, large driving force, and low rising velocity. The transfer coefficient (K L a) refers to the ability to transfer hydrogen gas to the liquid phase, which depends on the size of bubble (Cruz et al, 1999;Painmanakul et al, 2009). As such, the K L a of the microbubble reactor was 45×10 -3 s -1 , which is approximately 22.5 times greater than that of the millibubble reactor (2×10 -3 s -1 ).…”

Methods for Oxygenation of Continuous Cultures of Brewer’s Yeast, Saccharomyces cerevisiae

“…Recent reviews of bioreactor aeration discuss a variety of methods [4][5][6]. There are also many variables that can influence aeration including temperature, mixing rate, membranes, biomass concentration, and media [7][8][9][10]. In this study, we use a novel sensor array to compare different filter technologies and media to conventional methods to determine if the methods can be used in space to oxygenate yeast cultures.…”

“…Recent reviews of bioreactor aeration discuss a variety of methods [4][5][6]. There are also many variables that can influence aeration including temperature, mixing rate, membranes, biomass concentration, and media [7][8][9][10]. In this study, we use a novel sensor array to…”