Solids, transport processes with

Because of the basic requirements of collection and transport, sewer networks are normally dealt with from a physical point of view, i.e., the hydraulics and sewer solids transport processes have been focal points. From this point of view, new design and operational principles have been developed, to a great extent supported by numerical procedures and the ever-increasing capacity of computers. Under wet-weather conditions, the hydraulics and solids transport phenomena in a sewer play a major role, and the chemical and microbiological processes are typically of minor importance. Not surprisingly, interests devoted to urban drainage have focused on the physical behavior of the sewer. 

Microbial transformations and generally not chemical transformations characterize the sewer environment in terms of quality transformations of the wastewater. On the other hand, the physicochemical characteristics, e.g., diffusion in the biofilm and exchange of substances across the water-air interface, play an important role and must be integrated with the microbial transformations. The hydraulics and the sewer solids transport processes have a pronounced impact on the sewer performance. These physical processes, however, are typically dealt with in hydraulics and are, therefore, only included in the text when directly and closely related to the chemical and biological processes. 

Transport Processes with Reactions Catalyzed by Solids... 

CHAPTER 3 TRANSPORT PROCESSES WITH REACTIONS CATALYZED BY SOLIDS... 

The first one is a general methodology developed by Abu-Reziq et al [26,27] for the conversion of fully hydrophobic catalytic reactions - the catalyst, the substrate, and the product, are all hydrophobic - into a catalytic reaction that is carried out in water, eliminating the need for organic solvents. The method is based on a three-phase system composed of an emulsion (oil in water of the substrate and product molecule) and a solid (the catalysts), and was termed the EST (emulsion/solid transport) process. The idea (Figure 31.11) relies on the transport of hydrophobic substrates to an entrapped catalyst, and the transport of the resulting product from the catalyst porous solid back into the bulk. Specifically, the catalyst is entrapped inside a hydrophobically modified porous sol-gel matrix the hydrophobic substrate for that catalyst is emulsified in water in the presence of a suitable surfactant and the powdered catalytic sol-gel material is dispersed in that emulsion. Upon contact of the surfactant with the hydrophobic interface of the sol-gel matrix, it reorients and spills the substrate into the pores... 

Combined Pore and Solid Diffusion In porous adsorbents and ion-exchange resins, intraparticle transport can occur with pore and solid diffusion in parallel. The dominant transport process is the faster one, and this depends on the relative diffusivities and concentrations in the pore fluid and in the adsorbed phase. Often, equilibrium between the pore fluid and the solid phase can be assumed to exist locally at each point within a particle. In this case, the mass-transfer flux is expressed by ... 

Enantioselective transport processes can be achieved either with solid or liquid membranes (Fig. 1-5). In this latter case, the liquid membrane can be supported by a porous rigid structure, or it can simply be an immiscible liquid phase between two solutions with the same character (aqueous or nonaqueous), origin and destination... 

Figure 9-3 portrays a hypothetical model of how chemical weathering and transport processes interact to control soil thicknesses. The relationship between soil thickness and rate at which chemical weathering can generate loose solid material is indicated by the solid curve. The rate at which transport processes can potentially remove loose solid weathering products is indicated by horizontal dotted lines. The rate of generation by chemical weathering initially increases as more water has the opporhmity to interact with bedrock in the soil. As soil thick-... 

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