In this study, the characteristic and filtration behaviour of a newly developed ceramic nanofiltration membrane was studied and compared to other commercial ceramic nanofiltration membranes currently ...available. It could be shown that it was possible to produce a ceramic membrane with separation properties in the nanofiltration range and with permeability rates clearly superior to that of polymer nanofiltration membranes. The ceramic membrane was used in tests involving the treatment of textile wastewater, alkaline solutions from bottle washing machines and pickling bath solutions.
: In this paper we report on the characteristic and filtration behavior of a newly developed ceramic nanofiltration membrane and compare it with other commercial ceramic nanofiltration membranes ...currently available. It is shown that it is possible to produce a ceramic membrane with separation properties in the nanofiltration range and with permeability rates that are clearly superior to those of polymer nanofiltration membranes. The ceramic membrane was used in tests involving the treatment of textile wastewater, alkaline solutions from bottle washing machines, and pickling bath solutions.
: The modelling of membrane filtration processes is often performed by applying black‐box models or short‐cut methods, because of the complexity of the molecular interactions on and inside the ...membrane. The assumptions made for short‐cut methods can be applied with accuracy to reverse osmosis processes, whereas the simulation of nanofiltration can lead to unreliable results that sometimes deviate from real conditions to a great extent. A steady‐state process simulation, NF‐PROJECT, based on input information from membrane characterization, was developed (isothermal operation). The individual separation characteristics of each membrane element are calculated in an iterative sequence, illustrating the successive reduction in permeability and rejection between the elements arranged inside the pressure vessel. The simulation provides information on the increasing feed concentration and osmotic pressure, the hydraulic pressure loss, the deterioration of the flow conditions in the vessel, and the joint performance of the membrane elements to be analyzed. Taking an example from a practical application, a two‐stage nanofiltration pilot plant was simulated, the results of which are presented in this article. Examples of optimization potentials are illustrated for the target criteria of economic efficiency (specific energy costs), permeate quality, and flow.
Aqueous two-phase systems often face mass transfer limitations due to very poor miscibility of the fluids, and to enhance the homogeneity (or emulsification) in the reaction volume, high energy ...inputs are required which result in high shear forces in the culture medium. For the purposes of emulsification, microporous systems have advantages over other conventional methods due to mild operating conditions and narrow droplet-size distribution. In this study, emulsification within the culture volume was achieved by feeding the oily substrate (dispersed phase) into the aqueous medium (dispersion phase) via ceramic membranes integrated in the bioreactor. The method was investigated for bioprocesses aimed at producing rhamnolipids and polyhydroxyalkanoates (PHA). Better homogenization of the mixed volume and hence improved consumption of oily substrate was successful. Surfactants are produced by various bacterial cultures, especially
Pseudomonas aeruginosa
species, when oil is present as the only carbon source. Are surfactants produced only as a result of bacteria feeding on the oily substrate, or as a requirement to feed on the oily substrate, owing to their surface-active characteristics? This paper also intends to draw some conclusions in this respect.
The modelling of membrane filtration processes is often conducted by applying black-box models or short-cut methods because of its complexity due to molecular interactions on and inside the membrane. ...The assumptions made for the short-cut-methods are applicable for reverse osmosis, whereas the simulation of nanofiltration processes can lead to unreliable results, which sometimes deviate greatly from real conditions. A steady-state process simulation NF-PROJECT, which is based on input information from membrane characterisation, was developed (isothermal operation). The individual separation characteristics of every membrane element are calculated in iteration, which leads to reduction of permeability and rejection for every further element arranged in series inside the pressure vessel. The simulation provides information on the increasing feed concentration and osmotic pressure, the hydraulic pressure loss, the deterioration of the flow conditions along the feed side in the vessel and the combined performance of the membrane elements to be analysed. Serving as an example from practical applications, a two-stage nanofiltration pilot plant was simulated, the results of which will be presented. Examples of design and optimisation potentials will be illustrated for the target criteria of economic efficiency (specific energy costs), permeate quality and flow.
In the beverage industry, numerous alkaline solutions are generated in cleaning processes. The treatment of these alkaline cleaning solutions with the objective of recovery or improvement of their ...quality can be conducted using pressure-driven membrane processes. This paper focuses on the behaviour of additive components, used for the alkaline cleaning of returnable bottles, during filtration with pH-stable ultrafiltration (UF) and nanofiltration (NF) membranes. A flux decline, which was more pronounced initially, was observed for the UF membranes with a cut-off of 1 and 50 kDa. This can be attributed to concentration polarisation at the membrane surface and the adsorption of cleaning additive components, especially of a non-ionic surfactant. The most stable membrane permeability during filtration was achieved by a 0.2 kDa NF membrane. The UF membrane with a cut-off of 50 kDa showed the lowest rejection for the different cleaning additives (5–20%), whereas the NF membrane with a cut-off of 0.2 kDa showed the highest rejection (about 90%) for all cleaning additives.
In recent years, nanofiltration has increasingly gained in significance. To increase efficiency in process development, particularly for new fields of application, it has become essential to use ...calculation tools in conjunction with the process in question. The tool NF-PROJECT for the simulation of two-stage NF processes at industrial scale has already been developed and presented. Its suitability for practical application in process simulation was examined as an additional aid for process development, the results of which will be discussed in this paper. To this end, the simulation tool was applied in the treatment of spent process water from the food industry. In this case, NF-PROJECT was conducive to the selection of suitable nanofiltration membranes and to process optimization while significantly reducing the time span of process development.
