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.