A Low-Temperature and Low-Pressure Distillation Plant for Dairy Wastewater

The paper investigates an alternative treatment plant for the typical wastewater effluent of a cheese-making industry, mainly composed of acid or sweet whey mixed with washing water. Two variable parameters have been considered during the tests: four treatment temperatures (39, 46, 53 and 60 °C) and three solid content values (30%, 50% and 70%) of the concentrated product. The minimum and maximum values of the removal efficiency (pollutant amount into concentrate related to raw whey) range from 94.6% to 97.7% for conductivity, from 98.3% to 99.5% for BOD5, from 98.7% to 99.6% for COD and from 98.2% to 99.3% for Total Nitrogen. The plant capacity ranges from about 2 L/h (at 39 °C) to 6 L/h (at 60 °C) of processed whey. On the basis of the experimental findings, the proposed purification technology has demonstrated its suitability both to purify the effluent wastewater and to recover high-quality products (e.g., whey protein concentrate, lactose), thanks to its low thermal damage on the treated product and to its relatively low energy consumption from 0.4 kWh/L (at 60 °C) to 1.0 kWh/L (at 39 °C) of processed whey, with a Coefficient of Performance from approximately 0.6 up to 1.5.