Process-scale membrane filtration

Figure 2a. Flow Diagram of Two-Stage Pilot Scale Membrane Filtration Process for Recovery of an Extracellular Protease...

This chapter is concerned primarily with process scale membrane fihratinn and phenomena or effects that are relevant to such filtration. Cartridge filtration has already been discussed in Chapter 6, hence most of the following work refers to membrane filtration under crossflow conditions. Hiis technique is applicable to both microfiltration... 

While the ambient-temperature operation of membrane processes reduces scaling, membranes are much more susceptible not only to minute amounts of scaling or even dirt, but also to the presence of certain salts and other compounds that reduce their ability to separate salt from water. To reduce corrosion, scaling, and other problems, the water to be desalted is pretreated. The pretreatment consists of filtration, and may include removal of air (deaeration), removal of CO2 (decarbonation), and selective removal of scale-forming salts (softening). It also includes the addition of chemicals that allow operation without scale deposition, or which retard scale deposition or cause the precipitation of scale which does not adhere to soHd surfaces, and that prevent foam formation during the desalination process. 

The key process parameters for filtration scale-up are trans-membrane pressure, filtration area, shear rate, operating time, temperature, flux rate, protein concentration, and solution viscosity (5). 

This study focuses firstly on the transfer of regeneration principles as they have been developed in the field of water-based electroplating and of purification options for ionic liquids as they are experienced in other fields of ionic liquid application. A number of purification procedures for fresh ionic liquids have already been tested on the laboratory scale with respect to their finishing in downstream processing. These include distillation, recrystallization, extraction, membrane filtration, batch adsorption and semi-continuous chromatography. But little is known yet about efficiency on the technical scale. Another important aspect discussed is the recovery of ionic liquids from rinse or washing water. 

The development of the membrane production to real large-scale production will increase the realiability of membrane-filtration plants and increase the competitive power of the membrane-filtration process. 

In a recent study, which analyzed influent and effluent concentrations from drinking water treatment plants, it was concluded that only the treatment plants with membrane filtration removed PFCs efficiently [90]. However, PFCs analyzed did not include compounds with carbon chain lengths shorter than C6, thus not revealing the removal capacity for, e.g., PFBA and PFBS at process scale [90]. The generation of a concentrated waste stream when membrane filtration is used and the relatively high operation costs make this treatment method not widely used yet in the drinking water treatment process. 

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