Chemical and Biomolecular Engineering - Research Publications
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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.
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ItemEutectic freeze crystallization of saline dairy effluent(Elsevier, 2020-04-15)The disposal of saline effluent in the dairy industry is subject to increasingly strict regulatory requirements. In this work, eutectic freeze crystallization (EFC) was investigated as a mechanism for the simultaneous separation of salts and ice in a typical saline effluent, namely salty whey. Experiments were conducted using salty whey samples collected from a dairy processing facility. The eutectic point of the salty whey was determined using differential scanning calorimetry and was found to be lower than that of NaCl solutions (−24 °C for salty whey vs. −21 °C for aqueous NaCl solutions). Crystallization experiments were then used to construct the phase diagram of this dairy stream under equilibrium conditions. The change in cation composition in the supernatant at the eutectic temperature was measured as a function of time and showed that pure NaCl salts and ice formed within 5 min after this temperature was reached. The energy consumption of this process was estimated to be ~120 kWh/t for salty whey, which is comparable to that for conventional thermal crystallization of brine.
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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.
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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.
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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.
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ItemThe effect of restriction membranes on mass transfer in an electrodialysis with filtration membrane process(ELSEVIER SCIENCE BV, 2017-03-15)
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ItemRemoval of lactic acid from acid whey using electrodialysis(ELSEVIER SCIENCE BV, 2016-01-28)
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ItemCrystallisation of minerals from concentrated saline dairy effluent(PERGAMON-ELSEVIER SCIENCE LTD, 2016-09-15)An understanding of crystallisation within saline effluents is important for the design of both brine crystallisers and brine disposal ponds. In this work, crystallisation of a saline effluent concentrate from the Australian dairy industry has been examined at 22 wt% and 30 wt% total solids and at temperatures between 10 and 70 °C. The precipitation occurs more rapidly at higher temperatures. This trend is dictated by precipitation of calcium phosphate salts, albeit the major constituents of the mixture are NaCl and lactose. The crystallisation induction time can be shortened by introducing cavitation induced by ultrasound. In particular, the use of two short acoustic pulses between 3.7 J/g and 16 J/g at 20 kHz spaced ten minutes apart has maximum impact upon both induction time and crystal size. It is believed that the first ultrasound pulse either generates new nuclei or enhances the mass transfer of solute toward the surface of sub-micron growing crystals. Conversely, the second pulse disrupts the growing crystals and forms secondary nuclei. The ultrasound cannot shift the solution equilibrium and so is not able to improve the low crystal yield. To increase this total yield, further evaporation is necessary. The work provides direction to personnel in the dairy industry of the feasibility of brine crystallisation with respect to energy demand and solid recovery.