Oxygen transfer conditions

Bioreaction optimisation involves assessment of good oxygen transfer conditions and evaluation of shear stress influence on cell growth and productivity. 

Use of pure oxygen, (i.e., their UNOX system), was once proposed by Union Carbide for the rejuvenation of highly eutrophic lakes. Certainly, this system provided excellent oxygen transfer conditions, and was made feasible with the availability of low-cost processes for oxygen enrichment of air. More recently, the UNOX system has been used for rapid treatment of high BOD waste streams from a fully bleached kraft pulp mill before discharge [36]. 

The oxygen transfer rate for aerators is normally reported at standard conditions. Thus, ia order to make meaningful comparisons, the ORT under working or field conditions should be adjusted to standard conditions oxygen requirement for treatment (SORT) by means of... 

The SORT value when divided by the standard conditions oxygen transfer rate (OTR) given for a mechanical aerator yields the oxygen concentration required for treatment. 

As the oxygen transfer rate under steady-state conditions must equal oxygen uptake, K a may be calculated ... 

Once a plant is built, the conditions of agitation, aeration, oxygen transfer, and heat transfer are more or less set, and sterilization cycles are defined. Those environmental conditions achievable in plant-scale equipment should be scaled down to the pilot plant and laboratoiy equipment (shaken flasks) to insure that results can be translated. 

Benzoyl hydroperoxide was used for the conversion of divinyl sulphide into divinyl sulphoxide by Levin as early as 1930. In 1954 Bateman and Hargrave reported that saturated sulphides may be oxidized to sulphoxides by means of cyclohexyl or t-butyl hydroperoxide. These authors found that in both polar and non-polar solvents oxygen transfer occurred to give quantitative yields of sulphoxides over a wide range of experimental conditions according to equation 7. It was also reported that a quantitative yield of sulphoxides was obtained from the reaction of unsaturated sulphides with t-butyl and cyclohexyl hydroperoxides in methanol. With t-butyl hydroperoxide in benzene the sulphoxide yield was in no case stoichiometric, varying from 90 to 5% under the condition chosen. 

Organoboron compounds cannot react without proper activation. The use of oxygen bases is inherent in the standard Suzuki-Miyaura cross-coupling method. Fluorides (usually CsF) can be used as alternative activating agents, which is particularly useful in cases when the reagents are incompatible with oxygen bases for the reactions run under anhydrous conditions,24 (66) 241 Fluoride activation can be effective, however, even under aqueous phase-transfer conditions (67) 242... 

Special sewer structures like junctions, manholes, bends, weirs and drops may give rise to a turbulence that is increased compared with the hydraulic conditions that exist under normal sewer pipe flow. The turbulence introduced by these structures increases the air-water oxygen transfer, and the formulas in Table 4.7 are no longer valid. These special sewer structures typically have their own site-specific characteristics, and a simple empirical description of the reaeration at sewer drops and falls that includes only the most important parameters is needed. 

In Figure 8.3, the oxygen transfer coefficient, KLa, the flow velocity, u, the bulk water DO concentration and the DO consumption rate of the biofilm, ry, are all plotted versus the flow, Q, under steady state conditions in a gravity sewer pipe under the conditions given. 

---