Pilot Study on the Removal of Lactic Acid and Minerals from Acid Whey Using Membrane Technology

Acid whey presents a major disposal issue for the dairy industry due to its high lactic acid and mineral concentrations. In this work, the feasibility of using membrane technology to treat acid whey to produce high quality whey powder was demonstrated at pilot scale. Three process combinations were tested, namely, (1) ultrafiltration and electrodialysis; (2) ultrafiltration, nanofiltration, and electrodialysis; and (3) ultrafiltration, dia-nanofiltration, and electrodialysis. All three combinations were successful in reducing the levels of lactic acid and minerals in acid whey. However, the lowest ratio between lactic acid and lactose (0.017 g lactic acid/g of lactose) was obtained with the process that utilized dia-nanofiltration. The energy required for the electrodialysis of the ultrafiltration permeate and dia-nanofiltration retentate were comparable (7.5 and 7.8 kWh/tonne of feed, respectively). However, the dia-nanofiltration retentate was at least 3.5 times more concentrated than the ultrafiltration permeate, thus reducing the annual energy consumption and capital investment of the electrodialysis unit. The product of the nanofiltration and electrodialysis process was successfully dried to produce a powder with an ash and moisture content of 4% and 2.5%, respectively.