Dissolved oxygen dynamics

In a typical experiment by the dynamic gassing-in/gassing-out method during the normal operation of the plant, the air supply is shut off and the dissolved oxygen (DO) concentration is monitored as the DO is depleted. The dissolved oxygen dynamics during the gassing-out part of the experiment are described by... 

Subsequently, during the gassing-in part of the experiment, we can determine kLa. In this case, the dissolved oxygen dynamics are described by... 

Kemp, W.M., and Boynton, W.R. (1980) Influence of biological and physical processes on dissolved oxygen dynamics in an estuarine system implications for measurement of community metabolism. Estuar. Coastal Shelf Sci. 11, 407—431. 

Oxygen transfer rate (OTR) The product of volumetric oxygen transfer rate kj a and the oxygen concentration driving force (C - Cl), (ML T ), where Tl is the mass transfer coefficient based on liquid phase resistance to mass transfer (LT ), a is the air bubble surface area per unit volume (L ), and C and Cl are oxygen solubility and dissolved oxygen concentration, respectively. All the terms of OTR refer to the time average values of a dynamic situation. 

Almost all aquatic organisms rely on the presence of dissolved oxygen for respiration. Although oxygen is nonpolar, it is very slightly soluble in water and the extent to which it dissolves depends on its pressure. We have already seen (in Section 4.2) that the pressure of a gas arises from the impacts of its molecules. When a gas is introduced into the same container as a liquid, the gas molecules can burrow into the liquid like meteorites plunging into the ocean. Because the number of impacts increases as the pressure of a gas increases, we should expect the solubility of the gas—its molar concentration when the dissolved gas is in dynamic equilibrium with the free gas—to increase as its pressure increases. If the gas above the liquid is a mixture (like air), then the solubility of each component depends on that component s partial pressure (Fig. 8.21). 

Figure 17.4 PULSAR Measurements of Dissolved Oxygen (DO) Concentration During a Dynamic Gassing-in/Gassing-out Experiment.

Vacuum/pressure vs. distance VOC concentrations in soil and groundwater under static and dynamic conditions C02 and 02 in soil vapor Increase in dissolved oxygen (DO) levels... 

Biochemical oxygen demand (BOD) is one of the most widely determined parameters in managing organic pollution. The conventional BOD test includes a 5-day incubation period, so a more expeditious and reproducible method for assessment of this parameter is required. Trichosporon cutaneum, a microorganism formerly used in waste water treatment, has also been employed to construct a BOD biosensor. The dynamic system where the sensor was implemented consisted of a 0.1 M phosphate buffer at pH 7 saturated with dissolved oxygen which was transferred to a flow-cell at a rate of 1 mL/min. When the current reached a steady-state value, a sample was injected into the flow-cell at 0.2 mL/min. The steady-state current was found to be dependent on the BOD of the sample solution. After the sample was flushed from the flow-cell, the current of the microbial sensor gradually returned to its initial level. The response time of microbial sensors depends on the nature of the sample solution concerned. A linear relationship was foimd between the current difference (i.e. that between the initial and final steady-state currents) and the 5-day BOD assay of the standard solution up to 60 mg/L. The minimum measurable BOD was 3 mg/L. The current was reproducible within 6% of the relative error when a BOD of 40 mg/L was used over 10 experiments [128]. 

FIGURE 4.1 Application of computational fluid dynamics to simulate (A) bubble position after 120 s during O2 dosage at 26 mg/L/month and 670- tm bubble size (B) represents a diagonal slice of the wine phase velocity field, and (C) the dissolved oxygen concentration in milligram per liter. Reprinted with permission from Dykes and Kilmartin (2007). Copyright 2007 Winetitles Pty Ltd. 

Boicourt, W.C. (1990) The influences of circulation processes on dissolved oxygen in Chesapeake Bay. In Oxygen Dynamics in Chesapeake Bay, USA, A Synthesis of Recent Research (Smith, D.E., Leffler, M., and Mackiernan, eds.), pp. 1-59, Maryland Sea Grant, College Park, MD. 

A method of measuring kya which has gained wide acceptance in recent years is the dynamic method using fast dissolved oxygen probes. The rate of change of oxygen tension in a semibatch... 

Because modulation of enzyme activities depends on metabolite concentrations, which in turn are determined by the entire metabolic network, the overall response time for these controls can be on the order of seconds. This is the same as the time scale for changes in environmental conditions (e.g., pH, dissolved oxygen concentration) encountered by cells as they circulate through the nonuniform contents of a large-scale bioreactor. Therefore, beyond the complexities of enzyme activity control in the steady state, dynamic properties of this control system are important. The circulation pattern in a bioreactor has major effects on product formation [28]. Lack of understanding of transient responses of cell metabolism is one central obstacle to systematic scale-up of laboratory results (obtained in idealized,... 

With respect to whole cell biosensors utilising dissolved oxygen probes, Liang et al. reported a four-layer model to describe the signals from an oxygen probe used to transduce the respiratory activity of mouse leukaemia tumour cells [13]. This work was carried out with a view to using the biosensor to study the dynamic responses to various drugs. Finite difference methods were used to solve the material balances between the inner... 

Dynamic equilibria occur in all saturated solutions for instance, there is a continuous exchange of oxygen molecules across the surface of water in an open container. This is fortunate for fish, which breathe dissolved oxygen. 

A simple dynamical box-model was constructed in order to test the seasonal variation features of phytoplankton, zooplankton, DIN, DIP, DOC, POC, as well as dissolved oxygen (DO) in the northern part of Jiaozhou Bay in 1995. The annual variations of the phytoplankton production show two high value periods (Mar. to Apr. and July to Aug.) and two low value periods (May to July and after Oct ). DOC shows the common features it is high in summer and low in winter (Wu and Yu, 1999). Their model equations describing the cycles of phytoplankton and OC in the ocean are as follows ... 

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