Ozonation of C.I. Reactive Black 5 and Indigo

The ozone transfer for the ozonation of the azo dye Reactive Black 5 (RB5) and indigo was investigated using a bubble column at semi-batch conditions. The results were analyzed by applying film theory and surface renewal theory. The ozonation of both dyes was so fast that an instantaneous reaction directly at the bubble surface can be assumed. The ozone balance in the gas phase was used to determine the volumetric mass transfer coefficient k_La and the enhancement factor E. Besides the measured concentrations, temperature and pressure only the Henry coefficient was required for the determination of k_La and E. By varying the ozone inlet and the dye concentration the reaction regime was identified. The Hatta number Ha which requires uncertain parameters did not have to be determined.     

Biologische Denitrifikation nitrathaltiger Abwässer und Grundwässer

Biological denitrification of nitrate-containing waste water and ground water. The differing objectives serve to distinguish processes for the treatment of waste water and those for the production of drinking water. In waste water purification, frequent use is made of submerged reactors with deposition and recycling of bacteria. The carbon compounds required by the bacteria are either present in the water or have to be added. If the nitrogen is present as ammonium in the waste water, then there are several different ways of combining nitrification and denitrification reactors. In production of drinking water, both heterotrophic and autotrophic bacteria are used. Since the bacteria are not allowed to enter the supply network, fixed reactors or other reactors with immobilised biomass are used. Sand bed filters are still necessary to retain compounds from the water after denitrification.     

Development of Co-Cu-C-Mn Catalysts for the Synthesis of Higher Alcohols

Co-Cu catalysts represent a promising possibility to synthesize higher alcohols. In this study, novel carbon-embedded Co-Cu catalysts have been prepared and were tested in an 8-fold parallel reactor system. Moreover, the influence of Mn as a dopant on the catalytic performance has been studied. It was shown that Mn reduced the selectivity for methane and favored the formation of olefins. In contrast to Cu-free catalysts, Cu-containing catalysts have an improved selectivity for alcohols.     

Robust design of multilayer optical coatings by means ofevolutionary algorithms

Robustness is an important requirement for almost all kinds of products. This article shows how evolutionary algorithms can be applied for robust design based on the approach of Taguchi. To achieve a better understanding of the consequences of this approach, we first present some analytical results gained from a toy problem. As a nontrivial industrial application we consider the design of multilayer optical coatings (MOCs) most frequently used for optical filters. An evolutionary algorithm based on a parallel diffusion model and extended for mixed-integer optimization was able to compete with or even outperform traditional methods of robust MOC design. With respect to chromaticity, the MOC designs found by the evolutionary algorithm are substantially more robust to parameter variations than a reference design and therefore perform much better in the average case. In most cases, however, this advantage has to be paid for by a reduction in the average reflectance. The robust design approach outlined in this paper should be easily adopted to other application domains     

Hybrid ordered phase encoding (HOPE): an improved approach for respiratory artifact reduction

Respiration causes continuous change in cardiac position, which leads to image degradation. Phase-encode reordering methods are often used to reduce these artifacts. An improved method for suppressing motion artifacts by reordering the acquisition of k space has been developed that is less sensitive to change of breathing patterns and bulk movement. We describe the theory behind the new approach and compare its results with those of existing methods by use of a phantom with simulated and actual acquired breathing patterns. The comparison was also made in vivo; cardiac scans were performed in 15 subjects with image planes that are known to be particularly susceptible to respiratory artifact. A significant improvement in image quality was achieved compared with conventional nonreordered and existing reordering methods.     

Potential of OUR and OTR measurements for identification of activated sludge removal processes in aerated basins.

In order to develop a process control scheme to reduce energy costs for aeration in activated sludge systems with biological P removal, pre-denitrification and nitrification stages, the spatial distribution of carbon oxidation and nitrification was evaluated over a long full-scale plug flow aeration basin using an externally measured specific oxygen uptake rate (sOUR) and in basin measurement of the actual specific oxygen transfer rate (sOTR) with off-gas testing as well as with the calculated oxygen demand from NH4-N concentrations (sOTR(N)). Using a simple static model, a gas phase balance on oxygen and carbon dioxide, sOTR(N) values were also calculated from off-gas testing. Comparison of sOTR(N) to sOTR and sOUR for carbon oxidation (sOUR(C)) to nitrification (sOUR(N)) at different loading conditions allowed the oxidation processes to be followed over the three zones of the aeration basin. As expected, the distribution depended on the dissolved oxygen concentration (DO) in the basin. However, the major change was in the C-oxidation rate and not the nitrification rate. At a low DO, and when NH4-N was present in the zone, the amount of oxygen transferred for nitrification was nearly the same, but the overall sOTR was lower. The externally measured sOUR was only useful when it was differentiated into sOUR(N) and sOUR(C). sOUR(N) could be used to predict the nitrification rate in the basin. With further refinement, the gas phase balance model has potential to be used to monitor the degree of nitrification over the basin length. This can be integrated into a control scheme to reduce aeration costs by adjusting the DO setpoint according to loading conditions in the