scholarly journals The Influence of Optic and Polarographic Dissolved Oxygen Sensors Estimating the Volumetric Oxygen Mass Transfer Coefficient (KLa)

2016 ◽  
Vol 10 (8) ◽  
pp. 142 ◽  
Author(s):  
Gustavo Andrés Baquero-Rodríguez ◽  
Jaime A. Lara-Borrero
Keyword(s):  
Mass Transfer ◽  
Wastewater Treatment ◽  
Dissolved Oxygen ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Oxygen Transfer ◽  
Airflow Rate ◽  
Oxygen Probe ◽  
Aeration System ◽  
Oxygen Measurement

Aeration is usually the most energy intensive part of the wastewater treatment process. Optimizing the aeration system is essential for reducing energy costs. Field tests oriented to estimate parameters related to oxygen transfer are a common approach to compare aeration systems. The aim of this research is to assess the effect of dissolved oxygen probe lag on oxygen transfer parameter estimation. Experimental procedures regarding to process automation and control were applied to quantify dissolved oxygen probe lag. We have measured oxygen transfer in clean water, under a wide range of conditions (airflow rate, diffuser characteristics and diffuser density), with optic and polarographic sensors for dissolved oxygen measurement. The oxygen transfer was measured as per ASCE Standard procedures. Nonparametric statistical tests were used to compare the estimated volumetric mass transfer coefficient KLa with different sensors. According to the results, there is not significant influence of the probe lag (also known as time constant) or probe characteristics on the parameters used to assess oxygen transfer efficiency. This fact has great relevance in common practice of aerobic process for wastewater treatment because dissolved oxygen monitoring is used as an input for decision making related to the energy optimization in the aeration system. Findings from these tests contradict previous studies which claim that lag time in polarographic sensors for the dissolved oxygen measurement can bias estimate KLa.

scholarly journals Specific Oxygen Uptake Rate and Mass Transfer Coefficient in Activated Sludge System

2019 ◽  
Vol 4 (2) ◽  
pp. 24-32
Author(s):  
S.H. Tan ◽  
◽  
Jamaiatul Lailah M.J. ◽  
Aida Isma M.I. ◽  
◽  
...  
Keyword(s):  
Mass Transfer ◽  
Oxygen Uptake ◽  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Uptake Rate ◽  
Oxygen Transfer ◽  
Oxygen Uptake Rate ◽  
Specific Oxygen Uptake Rate

Activated sludge process is one of the effective methods in biological wastewater treatment and the impact of oxygen transfer through aeration process has the most important breakthroughs as it served as the largest consumer in the treatment. Aeration is an energy demanding process. Oxygen transfer into an activated sludge is a very challenging issue in the field of multiphase flows. Apart from the physical mass transfer phenomena between gas, liquid and solids phases, the transport mechanisms are also overlapped by time and temperature, varying microbial activity, impurity loads, adsorption and desorption processes. Oxygen uptake rate (OUR) for microbial population in the activated sludge system is important parameter to determine the amount of oxygen consumed during aerobic heterotropic biodegradation in the system. Evaluation of specific oxygen uptake rate (SOUR) and the volumetric mass transfer coefficient (KLA) of oxygen for three different wastewater treatment processes, namely conventional activated sludge (CAS), oxidation ditch (OD) and sequencing batch reactor (SBR) treating municipal wastewater in Kuala Lumpur have been carried out. In-situ and ex-situ measurement of pH, dissolved oxygen (DO), temperature, MLSS and MLVSS were carried out. In the activated sludge treatment, very low concentration of dissolved oxygen may cause the wastewater to turn septic resulting in death of bacteria or in active due to unstable anaerobic conditions. Conversely, an excessive dissolved oxygen may result to high energy and high 25 operating cost. Higher flowrate may also cause dissolved oxygen to rise, reducing the quality of sludge and slowing the denitrification process in the system. Results revealed that the OUR for SBR, OD and CAS were 9.582 mg O2 /L/hr, 10.074 mg O2 /L/hr and 13.764 mg O2 /L/hr, respectively. Low oxygen uptake rate indicates a low rate of microbial respiration. By computing the OUR, the mass transfer coefficient could be evaluated. It should be noted that among the treatment system in this study, the conventional activated sludge shows the highest mass transfer coefficient and specific oxygen uptake rate of 2.038 hr-1 and 15.605 mg O2 /g MLVSS/hr, respectively. Improving the oxygen transfer rate and reducing aeration in the system could achieve a cost-effective aeration system.

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

2007 ◽  
Vol 55 (11) ◽  
pp. 183-191 ◽  
Author(s):  
H. Zhu ◽  
T. Imai ◽  
K. Tani ◽  
M. Ukita ◽  
M. Sekine ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Liquid Film ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Oxygen Transfer ◽  
Structural Parameters ◽  
Volumetric Mass Transfer Coefficient ◽  
Aeration System ◽  
Film Forming ◽  
Oxygen Transfer Efficiency

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.

scholarly journals Gas–liquid mass transfer characteristics of aviation fuel scrubbing in an aircraft fuel tank

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Li Chaoyue ◽  
Feng Shiyu ◽  
Xu Lei ◽  
Peng Xiaotian ◽  
Yan Yan
Keyword(s):  
Mass Transfer ◽  
Dissolved Oxygen ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Oxygen Concentration ◽  
Gas Holdup ◽  
Aviation Fuel ◽  
Volumetric Mass Transfer Coefficient ◽  
Dissolved Oxygen Concentration ◽  
Liquid Mass Transfer

AbstractDissolved oxygen evolving from aviation fuel leads to an increase in the oxygen concentration in an inert aircraft fuel tank ullage that may increase the flammability of the tank. Aviation fuel scrubbing with nitrogen-enriched air (NEA) can largely reduce the amount of dissolved oxygen and counteract the adverse effect of oxygen evolution. The gas–liquid mass transfer characteristics of aviation fuel scrubbing are investigated using the computational fluid dynamics method, which is verified experimentally. The effects of the NEA bubble diameter, NEA superficial velocity and fuel load on oxygen transfer between NEA and aviation fuel are discussed. Findings from this work indicate that the descent rate of the average dissolved oxygen concentration, gas holdup distribution and volumetric mass transfer coefficient increase with increasing NEA superficial velocity but decrease with increasing bubble diameter and fuel load. When the bubble diameter varies from 1 to 4 mm, the maximum change of descent rate of dissolved oxygen concentration is 18.46%, the gas holdup is 8.73%, the oxygen volumetric mass transfer coefficient is 81.45%. When the NEA superficial velocities varies from 0.04 to 0.10 m/s, the maximum change of descent rate of dissolved oxygen concentration is 146.77%, the gas holdup is 77.14%, the oxygen volumetric mass transfer coefficient is 175.38%. When the fuel load varies from 35 to 80%, the maximum change of descent rate of dissolved oxygen concentration is 21.15%, the gas holdup is 49.54%, the oxygen volumetric mass transfer coefficient is 44.57%. These results provide a better understanding of the gas and liquid mass transfer characteristics of aviation fuel scrubbing in aircraft fuel tanks and can promote the optimal design of fuel scrubbing inerting systems.

Study of the Process of Wastewater Treatment with Activated Caron from Dimethylamine and Dimethylformamide in their Joint Presence

2021 ◽  
Vol 25 (2) ◽  
pp. 18-22
Author(s):  
Yu.V. Solovyova ◽  
V.P. Yustratov ◽  
N.S. Golubeva ◽  
I.V. Vasiljeva ◽  
E.V. Nazimova
Keyword(s):  
Mathematical Modeling ◽  
Mass Transfer ◽  
Wastewater Treatment ◽  
Activated Carbon ◽  
Aqueous Solutions ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Adsorption Column ◽  
Limiting Stage ◽  
Column Process

The regularities and mechanism of adsorption of dimethylformamide and dimethylamine by industrial activated carbon in their joint presence from aqueous solutions are considered. The characteristics of equilibrium adsorption, the limiting stage, and the mass transfer coefficient have been determined. The main parameters of the adsorption column process and the mode of continuous cleaning are calculated by the method of mathematical modeling.

The effect of microbubbles on gas-liquid mass transfer coefficient and degradation rate of COD in wastewater treatment

2016 ◽  
Vol 73 (8) ◽  
pp. 1969-1977 ◽  
Author(s):  
Kangning Yao ◽  
Yong Chi ◽  
Fei Wang ◽  
Jianhua Yan ◽  
Mingjiang Ni ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Wastewater Treatment ◽  
Activated Sludge ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Degradation Rate ◽  
Mass Transfer Rate ◽  
Cod Removal ◽  
Liquid Mass ◽  
Liquid Mass Transfer

A commonly used aeration device at present has the disadvantages of low mass transfer rate because the generated bubbles are several millimeters in diameter which are much bigger than microbubbles. Therefore, the effect of a microbubble on gas-liquid mass transfer and wastewater treatment process was investigated. To evaluate the effect of each bubble type, the volumetric mass transfer coefficients for microbubbles and conventional bubbles were determined. The volumetric mass transfer coefficient was 0.02905 s−1 and 0.02191 s−1 at a gas flow rate of 0.67 L min−1 in tap water for microbubbles and conventional bubbles, respectively. The degradation rate of simulated municipal wastewater was also investigated, using aerobic activated sludge and ozone. Compared with the conventional bubble generator, the chemical oxygen demand (COD) removal rate was 2.04, 5.9, 3.26 times higher than those of the conventional bubble contactor at the same initial COD concentration of COD 200 mg L−1, 400 mg L−1, and 600 mg L−1, while aerobic activated sludge was used. For the ozonation process, the rate of COD removal using microbubble generator was 2.38, 2.51, 2.89 times of those of the conventional bubble generator. Based on the results, the effect of initial COD concentration on the specific COD degradation rate were discussed in different systems. Thus, the results revealed that microbubbles could enhance mass transfer in wastewater treatment and be an effective method to improve the degradation of wastewater.

Sensitivity analysis of the WATER9 model: emissions of odorous compounds from passive liquid surfaces present in wastewater treatment plants

2018 ◽  
Vol 2017 (3) ◽  
pp. 903-912
Author(s):  
Milena J. Calvo ◽  
Ademir A. Prata ◽  
Leonardo Hoinaski ◽  
Jane M. Santos ◽  
Richard M. Stuetz
Keyword(s):  
Mass Transfer ◽  
Wastewater Treatment ◽  
Liquid Phase ◽  
Wind Speed ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Wastewater Treatment Plants ◽  
Effective Diameter ◽  
Odorous Compounds ◽  
Liquid Surfaces

Abstract Empirical mathematical models have been frequently used to estimate emissions and to act in the prevention of possible impacts from odorous compounds. Based on the regulatory WATER9 model, the present study had the aim to evaluate the deviations originating from the simplification of using the effective diameter (in contrast to the conceptually appropriate use of the linear physical fetch) as fetch parameter in the calculation of the global mass transfer coefficient at passive liquid surfaces at wastewater treatment plants (WWTPs). The present analysis incorporated the influence of different values of wind velocity, molecular diffusivity and Henry's Law constant. The analyses for the calculation of the mass transfer coefficients were developed for 1,000 wind speeds, chosen using the Monte Carlo method, three WWTPs and three compounds of environmental relevance, spanning different behaviour regarding their volatilisation. The wind speed had a direct influence on the deviations for all types of compounds analysed. However, this parameter was found to be more representative for the compounds whose volatilisation is limited by conditions in the liquid phase. Furthermore, the deviations for the calculation of the mass transfer coefficient arising from the use of the effective diameter as fetch parameter were significantly larger for liquid phase-dominated compounds, compared to gas phase-dominated compounds. Comparison against available experimental data confirm that the use of the effective diameter as the fetch parameter makes the model predictions further depart from the experimental values. The present analysis shows that, for a varied range of wind speed and WWTP configurations, the use of the actual physical fetch shall be preferred over the use of the effective diameter in emission models for WWTPs, so as to avoid the introduction of potentially large systematic deviations.

Oxygen transfer in high-speed fermenter under steady cultivation conditions

1987 ◽  
Vol 52 (11) ◽  
pp. 2654-2663
Author(s):  
Pavel Seichter
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Oxygen Pressure ◽  
Oxygen Transfer ◽  
High Speed ◽  
Suggested Method ◽  
Cultivation Conditions ◽  
Fermentation Conditions ◽  
Partial Oxygen

A method for volume mass transfer coefficient calculation under steady fermentation conditions, including correction of partial oxygen pressure in bubbles, has been developed. Number of continuous cultivations on ethanol and sulphite substrates were evaluated on the basis of the suggested method.

Sign in / Sign up

Export Citation Format

Share Document