Dissolved oxygen concentrations levels

Fig. 3.6. Experimental data for dissolved oxygen concentration level in liquid phase at 5 and 10 1/m.

The aeration requirements of the deep shaft (vertical shaft bioreactor using flotation technology) are provided by two, 100 hp rotary screw compressors rated at a pressure of 7 kg/m2 (100 psig). Dissolved oxygen (DO) levels of 4 mg/L are maintained in the head tank, and during the startup phase of the plant a DO meter measured a dissolved oxygen concentration of 25 mg/L at the shaft bottom. 

As an illustration, let us take a look at a bioreactor (Fig. 1.1). To find out if the bioreactor is operating properly, we monitor variables such as temperature, pH, dissolved oxygen, liquid level, feed flow rate, and the rotation speed of the impeller. In some operations, we may also measure the biomass and the concentration of a specific chemical component in the liquid or the composition of the gas effluent. In addition, we may need to monitor the foam head and make sure it does not become too high. 

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... 

Thirteen liters of medium was sterilized for 20 min. at 121°C in a 20 L Chemap fermenter. The medium was cooled to 36 C and maintained at that temperature throughout the fermentation. The pH was maintained at 6.9 with 5M NaOH. The dissolved oxygen concentration was maintained at the prescribed level by agitation RPM adjustments (min. 400, max 700 RPM) and the ad tion of air/02. The glucose concentration was maintained between 10 to 20 g/L. 

Besides the assumptions for the cells, the medium is formulated so that only one component may be limiting the reaction rate. All other components are present at sufficiently high concentrations, so that minor changes do not significantly affect the reaction rate. Fermenters are also controlled so that environmental parameters such as pH, temperature, and dissolved oxygen concentration are maintained at a constant level. 

In the glucose oxidase system, dissolved oxygen concentration as well as glucose levels will influence dehvery response requiring close control of mass-transfer limitations. For both systems containing a protein component, stabihty factors may limit operational hfetime. This may be particularly severe in the case of glucose oxidase where the reaction product H2O2 will accelerate enzyme denaturation unless it is rapidly removed by diffusion or reaction with a second enzyme (peroxidase or catalase). 

A recirculating methodology is an attempt to maintain the water quality of the test solution without altering the toxicant concentration. A filter may be used to remove waste products or some form of aeration may be used to maintain dissolved oxygen concentration at a specified level. The advantage of this system is the maintenance of the water quality of the test solution. Disadvantages include an increase in complexity, an uncertainty that the methods of water treatment do not alter the toxicant concentration, and the increased likelihood of mechanical failure. 

Depending on the inhibitory concentration of 02 and the rate of 02 evolution, aeration gis composition, aeration rate and agitation can be optimized to keep the dissolved oxygen concentration at the desired level. If need be, various types of 02 scavengers such as sodium... 

This bioluminescent system has been widely used as reporter system for the detection of pollutants because of its high sensitivity. The co-substrate (FMNH2) and substrate (R-CHO) required for this reaction do not accumulate in the cell, but their levels depend on the level and balance of metabolism. Thus the bioluminescent reaction is directly linked to the cells metabolic activity, and so in models using lux as the reporter system, the light emission capacity is directly affected by factors such as changes in cell growth and dissolved oxygen concentration (Nelson and Lawrence, 1980). 

Carbon dioxide produced in an aerobic fermentor should be desorbed from the broth into the exit gas. Figure 12.2 [11] shows, as an example, variations with time of the dissolved C02 and oxygen concentrations in the broth, C02 partial pressure in the exit gas, and the cell concentration during a batch culture of a bacterium in a stirred fermentor. It can be seen that the C02 levels in the broth and in the exit gas each increase, while the dissolved oxygen concentration in the broth decreases. 

---