Chemical and Biomedical Engineering - Research Publications
Permanent URI for this collection
Search Results
1 - 10 of 11
-
ItemThe application of forward osmosis to dairy processing(Elsevier, 2020-09-01)This work assesses the feasibility for concentrating process streams within dairy processing facilities using commercial forward osmosis membranes; to increase their total solids concentrations before entering energy intensive unit operations including thermal evaporators and spray dryers. These streams include demineralised whey, lactose, whey protein concentrate, sweet whey and skim milk. FTSH2O cellulose acetate (CTA) and Aquaporin flat sheet membranes are used with magnesium chloride concentrations of 1.66 ± 0.12 M as the draw solution. The experimental data are fitted to conventional mathematical models for forward osmosis, further modified by considering the nonlinear relationship between osmotic pressure and solute concentration. The diffusion coefficients of magnesium chloride in 1.6 M solutions at 10 °C, 20 °C and 50 °C are obtained and reported for the first time. Minimal fouling and a significantly smaller degree of concentration polarisation was observed on the membrane surface during lactose concentration compared to the concentration of other dairy solutions, due to the absence of proteins and calcium phosphate salts. The transfer of magnesium into the concentrated products was monitored and shown to be below 100 mg per 100 g dry powder. Acid cleaning alone was not effective in recovering pure water flux, and enzyme cleaners at neutral pH were needed given the limited pH tolerance (3–8) of the CTA membranes. Total solids concentrations of the concentrated dairy streams by forward osmosis (up to 40%) exceed those which can be achieved by nanofiltration and reverse osmosis (i.e., 15–20%). This study shows that forward osmosis is an effective approach to concentrate relevant dairy streams to achieve high concentration factors (e.g. >4 for sweet whey samples) without jeopardising product quality.
-
ItemUtilisation of salty whey ultrafiltration permeate with electrodialysis(Elsevier, 2019-12-01)Salty whey is a waste by-product that incurs increasingly high disposal costs for the dairy industry. This study investigated electrodialysis of the ultrafiltration permeate of salty whey as either a concentrate for the treatment of sweet whey or as a source of lactose and salt. The type of concentrate (0.1 m NaCl or salty whey permeate) did not affect the rate of sweet whey demineralisation or the energy consumed per tonne of whey, but less sodium and more divalent cations were removed when salty whey permeate was used as the concentrate. Salty whey permeate could be effectively demineralised using either 0.1 m NaCl or a second stream of salty whey permeate as the concentrate. The concentrate purity could be enhanced using monovalent selective membranes without increasing the energy consumption of the process (3.2 ± 0.3 kWh per kg of NaCl removed from the diluate at 15 V).
-
ItemSeparation Technologies for Salty Wastewater Reduction in the Dairy Industry(Taylor & Francis, 2019-10-02)The wastewater discharged by cheese manufacturing processes is highly saline. This waste is generated from whey demineralization, chromatography and clean-in-place processes. Salty effluent can be diluted with other effluents and discharged as trade waste but the high salinity can trigger penalties imposed by local water authorities. Alternatively, such waste can be sent to evaporation ponds, but in some areas in Australia, environmental impacts regarding land degradation, odor and dust have prevented further pond construction. Similar concentrate and brine management issues are emerging in the seawater desalination and mining industries. This paper reviews a range of commercial and emerging separation technologies that may be suitable to both reduce the costs of salty wastewater treatment and to improve the recoveries of dairy and salt-based products. These technologies have been commercialized or applied at a laboratory scale to the fields of desalination and brine concentration. Each technology is discussed in terms of its principle of operation and suitability for treating high-salinity dairy wastewater. The potential energy requirement and processing cost of each technology is identified with respect to feed water salinity, to provide additional insights into the energy and cost efficiencies of these technologies.
-
ItemFouling and in-situ cleaning of ion-exchange membranes during the electrodialysis of fresh acid and sweet whey(ELSEVIER SCI LTD, 2019-04-01)This work investigated the fouling of ion-exchange membranes during the electrodialysis of sweet and acid dairy whey. Fresh whey was used, rather than solutions made up in the laboratory, giving a unique perspective. While membrane fouling occurred in all experiments, the effects on system performance were limited. Reductions in the current during pure NaCl circulation fell to a minimum of 80% of the original value after 5 h of whey processing. The use of an alkaline concentrate resulted in the strongest increase in system resistance, but the mineral deposits formed appeared to detach readily, thereby reducing these effects. The use of an acidic concentrate gave significantly greater rates of lactic acid removal, which is important in industrial applications. A solution of HCl with a pH of 1.0 ± 0.15 was effective for in-situ cleaning of the mineral deposits. However, protein deposits were not readily removed using the recommended base cleaning formula of 3% NaCl at a pH of 9.2 ± 0.2.
-
ItemAn investigation of the impact of fouling agents in capacitive and membrane capacitive deionisation(Elsevier, 2019-05)The effect of organic fouling on both capacitive deionisation (CDI) and membrane capacitive deionisation (MCDI) was studied using two model foulants, the sodium salt of alginic acid and humic acid. Fouling of the activated carbon electrodes in the CDI cell was significant. The salt adsorption fell to 75% and the charge efficiency to 90% of their initial values after 18 cycles of operation with 0.5 mM CaCl 2 and 60 mg L −1 of sodium alginate. Similarly, the salt adsorption fell to 70% and the charge efficiency to 65% of their initial values after 18 cycles of operation with 60 mg L −1 of humic acid. The effect on MCDI was much more limited with these two foulants. The ability to clean the CDI cell with alkali cleaning agents was also investigated. While this cleaning was effective in restoring the salt adsorption, the alkali solution caused erosion of the activated carbon electrode or its PVDF binder, evidenced by an accumulation of carbon within the cleaning solution. Alternative electrode designs or alternative cleaning solutions will be needed if this approach is to be used in systems with similar foulants.
-
ItemA pilot scale study on the concentration of milk and whey by forward osmosis.(Elsevier, 2019-05-15)The concentration of skim milk and whey was investigated at a pilot scale using forward osmosis membranes with an installed membrane area of 24 m2. The pilot plant was operated in batch mode using a draw solution (48–57 g/L of NaCl) that mimics the potential brine streams available in a dairy processing plant. This approach avoids or limits the need for the regeneration of a synthetic draw solution. A concentration factor of ∼2.5 was achieved for both the skim milk and fresh whey, resulting in a total solids concentration of ∼21 wt% and 15 wt%, respectively. Increasing the transmembrane pressure was found to be effective in improving the water flux, whereas a much greater increase in the draw solution osmotic pressure would be needed to achieve the same enhancement of flux. This study also showed that small organic molecules, such as lactose, were not fully rejected by the forward osmosis membranes. A cleaning protocol was established for recovering the membrane performance after milk and whey concentration. The specific energy required for milk and whey concentration using only the forward osmosis step (5–10 kWh/t water removed) is much lower than that required by reverse osmosis. Forward osmosis is an energy efficient and effective process for dairy applications if unlimited access to a brine stream can be made available within or in the proximity of dairy processing plants.
-
ItemA review of salty waste stream management in the Australian dairy industry(ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2018-10-15)Saline wastewater is a by-product of cheese manufacturing and whey processing that can have serious environmental and economic consequences. Salty streams originating from dairy processing operations include chromatography wastes, clean-in-place wastewater, acid whey, salty whey and waste generated from whey demineralization processes such as nanofiltration, electrodialysis and ion exchange. With the participation of the major dairy companies in Australia, an industry wide survey was conducted to acquire a comprehensive understanding of the management strategies for these salty waste streams. High salinity waste streams are commonly directed to evaporation ponds. However, environmental impacts from land degradation, odour and dust have prevented the construction of further evaporation ponds in some areas of Australia. The survey results also show that disposal to municipal trade waste is not always effective, as the current levels of some salinity-related parameters are significantly higher than the levels allowed by the local water/environmental authorities. For high salinity streams, salt removal can lead to more substantial savings in trade waste charges compared to wastewater volume reduction. Thus, salt removal and recovery from salty waste streams has become a major focus of the sustainability agenda of the Australian dairy industry.
-
ItemSpray assisted layer-by-layer assembled one-bilayer polyelectrolyte reverse osmosis membranes(ELSEVIER SCIENCE BV, 2018-10-15)
-
ItemEffects of industrial gas impurities on the performance of mixed matrix membranes(ELSEVIER SCIENCE BV, 2018-03-01)
-
ItemThe Role of Ion Exchange Membranes in Membrane Capacitive Deionisation(MDPI, 2017-09)Ion-exchange membranes (IEMs) are unique in combining the electrochemical properties of ion exchange resins and the permeability of a membrane. They are being used widely to treat industrial effluents, and in seawater and brackish water desalination. Membrane Capacitive Deionisation (MCDI) is an emerging, energy efficient technology for brackish water desalination in which these ion-exchange membranes act as selective gates allowing the transport of counter-ions toward carbon electrodes. This article provides a summary of recent developments in the preparation, characterization, and performance of ion exchange membranes in the MCDI field. In some parts of this review, the most relevant literature in the area of electrodialysis (ED) is also discussed to better elucidate the role of the ion exchange membranes. We conclude that more work is required to better define the desalination performance of the proposed novel materials and cell designs for MCDI in treating a wide range of feed waters. The extent of fouling, the development of cleaning strategies, and further techno-economic studies, will add value to this emerging technique.