There has been a huge expansion in acid whey production due to the rapid growth in Greek yogurt manufacture, therefore it is critical to find an economically feasible way to process acid whey. The objective of this study was to determine the suitability of novel experimental nanofiltration (NF) membranes to reduce the calcium content of acid whey, so that value added streams (e.g., lactose) could be produced from this whey. Approximately 1,000 L of acid whey was obtained from a local Greek yogurt manufacturer for each trial. A 10,000 Da UF membrane was used to produce a permeate stream (i.e., remove any residual proteins). Acid whey was then processed by one of 4 different NF membranes. Three novel NF membranes were evaluated for divalent ion permeation and compared with a control NF membrane. Permeates were concentrated to 1× and 2×, and were sampled at processing pressures of 1380, 2760 and 4140 kPa, and at operating temperatures of 4, 21, 43 and 54°C. Flux also was recorded. Total solids, lactose, galactose, lactic acid and calcium contents of the NF permeates/ retentates were determined. The calcium/lactose ratio in the permeate was determined. We wanted a high ratio of calcium to lactose in the permeate so that we could successful reduce the ash content of acid whey while retaining lactose. Higher temperatures and higher pressures yielded higher rates of component permeation for each type of membrane. The novel NF membranes had higher permeation of all components, compared with the control NF membrane. Lactose and calcium permeated the novel NF membranes to differing degrees, in contrast to the control NF membrane. Permeates were further concentrated (6×) by 1 of 2 novel membranes, or a control membrane. The composition of final concentrates and samples taken during the process of concentration were analyzed. The results indicated that the novel membranes had good retention of lactose while calcium permeation increased as the permeate concentration increased. Lactose hydrolysis tests were performed on NF concentrates of acid whey by utilizing a commercially available lactase enzyme with an acidic pH optimum. The end product of this hydrolysis was a dairy syrup with enhanced sweetness.