Desalination of whey by electrodialysis and ion exchange resins: analysis of both processes with regard to sustainability by calculating their cumulative energy demand

Desalination of whey is an important process in food technology and can be done either by electrodialysis (ED) or by ion exchange (IE) resins. The aim of the present paper is an assessment of the cumulative energy demand of both processes for a technical plant including production of the regeneration agents for the ion exchangers and treatment of waste water. A flow of 45 m3 per day of nanofiltered whey, which is three times concentrated and partially desalted, is assumed as feed for the plant. Data for the assessment was obtained from own laboratory experiments to be reported here, as well as from commercial plants. Applying IE, the final whey product is desalted to a degree of 99%. The IE process yields 3.7 m3 of waste water with 36.3 kg ash and an organic charge of 26 kg chemical oxygen demand (COD)/m3 feed whey. The energy demand of IE amounts to 0.15 kWh for pumping, 25.33 kWh for the production of the regenerants, and 9.75 kWh for the reduction of the organic charge/m3 whey. With ED, the final whey product is desalted to only 90%. ED yields 1.25 m3 of waste water with 8.1 kg ash and an organic charge of 8.4 kg COD/m3 whey. The energy demand of ED amounts to 4.2 kWh for pumping, 5.38 kWh for the electric current through the ED cells, and 3.16 kWh for the reduction of the organic charge/m3 whey.