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.
Illustration: Continuous production of lactobionic acid from oxidation of lactose via the flavoenzyme cellobiose dehydrogenase (CDH) was achieved. The enzyme is regenerated to its active (oxidized) ...state when the redox mediator (Med) accepts the electrons, and further oxidized at the anode. This electrochemical process promises to be cost-effective and more environmentally friendly as compared to enzymatic processes reported for the same purpose.
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This study focussed on the continuous electrochemical regeneration of cellobiose dehydrogenase, which has excellent biocatalytic properties. Conversion of lactose to latobionic acid was used to measure catalytic activity. The results obtained were compared with the results for the enzymatic regeneration method. Moreover, medium components were optimised using response surface methods for the turnover frequency of the biocatalyst. No loss of activity for the biocatalyst was observed due to contact with electrodes. Overall, this electrochemical process promises to be easier to control, more cost-effective and environmentally friendly than enzymatic processes. The product lactobionic acid can be widely applied because of its non-toxic and biodegradable character.
Scarcity of water is becoming an increasingly serious problem in many Asian countries. The situation is aggravated further by the pollution of fresh water resources due to the discharge of untreated ...wastewater from industrial enterprises and municipal wastewater. These problems have become worse since ground water reservoirs are also exhausted. The concurrent wastewater treatment and water re-use secures the sufficient availability of fresh water. A EU-founded project (Asia-Pro-Eco-programme, contract number: VN005/104759) was created to conduct a feasibility study for introduction of membrane-supported bioreactor technology (MBR) under tropic conditions. The study will reveal: (1) whether and in which way membrane bioreactors can be applied under tropic conditions to treat municipal wastewater; (2) the possibility of the adaptation of MBR technology to the technical, climatic and socio-economic circumstances of Asia; (3) in general the introduction of modern wastewater treatment plants will improve the environmental situation in Asia. A pilot plant was constructed and built in Vietnam with Vietnamese workers. MBR technology was chosen because it allows to build up decentralised wastewater treatment plants in areas where no municipal sewage system exists. It provides improved health conditions due to a almost bacteria-free effluent and the possibility of re-using the treated water.
: 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.
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.
