Dissolved oxygen levels

Stress Corrosion Crocking. Stress corrosion cracking occurs from the combined action of corrosion and stress. The corrosion may be initiated by improper chemical cleaning, high dissolved oxygen levels, pH excursions in the boiler water, the presence of free hydroxide, and high levels of chlorides. Stresses are either residual in the metal or caused by thermal excursions. Rapid startup or shutdown can cause or further aggravate stresses. Tube failures occur near stressed areas such as welds, supports, or cold worked areas. 

A suitable means of scale-up for aerobic processes is to measure the dissolved oxygen level that is adequate in small equipment and to adjust conditions in the plant until this level of dissolved oxygen is reached. However, some antibiotic fermentations and the production of fodder yeast from hydrocarbon substrates have very severe requirements, and designers are hard-pressed to supply enough oxygen. 

If refined products, such as gasoline, diesel, jet fuel, or kerosene, are transported in a pipeline, where otherwise sour hydrocarbon fluids are transported, there may be an undesired enrichment of sulfur in the refined products. This can be avoided if the oxygen level of the transportant is maintained at below 20 ppm [570]. The dissolved oxygen level in the hydrocarbon product is controlled by reducing the amount of air injection employed in mercaptan or disulfide reduction or by the use of oxygen scavengers prior to the introduction of the refined hydrocarbon product into the pipeline. 

The results of the calculation are plotted in Figure 4-2. Dissolved oxygen levels out at a value of about 0.2 mole/m3. The average length of time... 

Selecting an approach The in situ dissolved oxygen monitors in the river near the area of the kill report normal dissolved oxygen levels. 

Most of the studies05,20 271 show that a correlation between culture fluorescence and biomass concentration can be obtained mainly in the exponential growth phase. In addition, in order to obtain reproducible correlations, all of the fermentation conditions such as initial substrate concentration, pH, dissolved oxygen level, temperature, and agitation rate have to be the same. However, once the culture is past exponential growth, biomass measurement by following culture fluorescence is no longer accurate. 

Continuous culture systems of aerobic treatment are likely to be more cost effective since in steady state conditions the respiration rate and hence oxygen requirement, remain constant. This report describes the effects of mean treatment time, treatment temperature and dissolved oxygen level in aerobic continuous culture systems on the removal of odorants from piggery slurry and on the heterotrophic oxygen demand during treatment. 

The selection of the most appropriate mean treatment time, reaction temperature and dissolved oxygen level to be maintained in the aerated mixed liquor requires a clear definition of the treatment objectives for each particular farm enterprise. These are the... 

Samples of treated slurry were obtained from laboratory-scale continuous culture reactors (3 15 litres) during a series of treatments studying the effects on residual slurry quality of mean treatment time, reaction temperature, dissolved oxygen level and pH value (27). Some were also collected from a 2.4m3 pilot plant which was operating at 35°C and 7 day residence time and with dissolved oxygen saturation of 0 to 40%. The pilot plant was treating separated stored piggery slurry (TS 21 g/1 COD 26 g/1 ). 

Monitor dissolved oxygen levels regularly. Dissolved oxygen levels in water are affected by elevation, temperature, and salinity (17). Maintain values between 4 and 7.8 mg/L levels near the higher end of that range are especially favorable to health. 

Dissolved oxygen levels ranging between 0.37 and 1.28 ppm, depending on the contaminant and concentration... 

Wines on Dissolved Oxygen Levels, Amer. J. Enol. Viticult. (1960) 11, 164-169. 

While the dissolved oxygen level of the fermenter is steady, if you suddenly turn off the air supply, the oxygen concentration will be decreased (Figure 9.7) with the following rate... 

Because of this increased attention, major reductions were made in pollutant inputs, and by the 1970s some results were clear. Oil slicks disappeared dissolved oxygen levels improved odor problems were eliminated beaches reopened and algal mats disappeared. Buoyed by these successes, attention... 

Since crushed basalt has been recommended as a major backfill component (1), experiments were completed to evaluate the rate of dissolved oxygen consumption and the redox conditions that develop in basalt-water systems under conditions similar to those expected in the near-field environment of a waste package. Two approaches to this problem were used in this study (l)the As(III)/As(V) redox couple as an indirect method of monitoring Eh and (2) the measurement of dissolved oxygen levels in solutions from hydrothermal experiments as a function of time. The first approach involves oxidation state determinations on trace levels of arsenic in solution (4-5) and provides an estimate of redox conditions over restricted intervals of time, depending on reaction rates and sensitivities of the analyses. The arsenic oxidation state approach also provides data at conditions that are more reducing than in solutions with detectable levels of dissolved oxygen. 

The simulated groundwater used in these experiments was prepared to represent the compositon of groundwater from Well DC-6, Grande Ronde Formation, which samples water primarily from 200 m below the Umtanum unit on the U S DOE Hanford site near Richland, WA (1) Its composition is shown in Table II The groundwater used in these experiments was continually sparged with N2 gas before it entered the apparatus to reduce the dissolved oxygen level and to limit CO2 pickup ... 

Aeration and agitation are two important operations in animal cell culture. Oxygen has a low solubility in aqueous media, with a saturation concentration of approximately 7 mg Lr1 at 37°C. This implies that the oxygen must be provided continuously to the cultures, to ensure that the dissolved oxygen levels in the culture medium remain at an adequate level. The mass balance for oxygen in the liquid phase can be written as ... 

Dissolved oxygen levels in water depend, in part, on the chemical, physical and biochemical activities occurring in the water. Oxygen has a limited solubility in water directly related to atmospheric pressure and inversely related to water temperature and salinity. Low-dissolved oxygen levels can limit the bacterial metabolism of certain organic compounds. 

With shikonin, shear effects bein to limit productivity at a kLa of only 10 hr 1 in a shake flask culture. Therefore, if shear limitations can be overcome, at least a 30-fold improvement in productivity should be possible. This is the challenge b This represents 25% utilization of O2 in sparged air. c This represents 20% of saturation dissolved oxygen level. 

Regnell O. 1994. The effect of pH and dissolved oxygen levels on methylation and partitioning of mercury in freshwater model systems. Environ Pollut 84 7-13. 

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