A study of the separation of lactose from whey ultrafiltration permeate using nanofiltration

Whey is the main by-product obtained from cheese production. It contains a high concentration of organic matter, mainly proteins and lactose, and mineral salts. Usually, pre-treated whey was discharged into sewer together with the other liquid effluents from the dairy industry. However, the increasingly stringent legal standards for wastewaters in contrast with the high COD and BOD of whey have entailed a change in the approach to whey management. The present paper is focused on the study of the concentration and diafiltration processes applying nanofiltration (NF) membranes for whey after its ultrafiltration. The NF membrane used in all experiments was DS-5 DL from GE-OSMONICS. For each test, different transmembrane pressures ranging between 0.5 and 2.5 MPa were tested. Results indicated that both the lactose concentration and the whey demineralization were achieved for a combination of the concentration and continuous diafiltration modes. The best operating conditions for the process (those entailing the lowest lactose loss) were 2 MPa and a VDF of around 2. Higher volume dilution factor (VDF) implied higher chloride removal from the whey but at the same time a lactose loss increase.

NF process was effective for mineral salts removal from whey with the aim of reusing lactose. In this way, three operation modes were studied: total recycle, concentration and continuous diafiltration. Combining the concentration and CDMs, the lactose concentration and the whey demineralization are achieved. The best operating conditions for the process (those entailing the lowest lactose loss) were 2 MPa and a VDF of around 2. Higher VDF implied higher chloride removal from the whey but at the same time a lactose loss increase. A further treatment of the NF permeate streams is required in order to discharge it into sewer because of their COD measured values. However, permeates can be reused in cheese processing. Fouling problems were not detected for the performed NF tests. However, longer experiments in a larger scale plant have to be performed to [1] H. Roginski, J.W. Fuqua and P.F. Fox, Encyclopedia of dairy sciences, Academic Press, London, 2003. [2] S.C. Marshall, Applying membrane processes: the first steps, Aust. J. Dairy Technol., 4 (1997) 50 Á 52. [3] J.G. Zadow, Whey and lactose processing, Elsevier Applied Science, New York, 1992. [4] R. Jeantet, P. Schuck, M.H. Famelart and J.L. Maubois, Intr^t de la nanofiltration dans la ee production de poundres de lactoserum deminralises, Le lait 80 (2000) 155 Á 163. e e [5] H.C. van der Horst, J.M.K. Timmer, T. Robbertsen and J. Leenders, Use of nanofiltration for concentration and demineralisation in the dairy industry: model for mass transport, J. Membr. Sci., 245 (1995) 205 Á 218. [6] J. Timmer, Properties of nanofiltration membranes; model development and industrial application. PhD thesis, Technische Universiteit Eindhoven, 2001. [7] R. Atra, G. Vatai, E. Bekassy-Molnar and A. Balint, Investigation of ultra- and nanofiltration for utilization of whey protein and lactose, J. Food Eng., 67 (2005) 325 Á 332.