Clean water recycle in sugar extraction process: Performance analysis of reverse osmosis in the treatment of sugar beet press water☆

Abstract In the beet sugar manufacturing the treatment of the press water represents a challenging design task. In fact presently, press water is completely recycled to the extraction of sugar beet cossettes. Press water is essentially a dilute solution (1–3% total solids) containing, besides sugar (60–80% of the total solids), impurities in the form of dissolved species, salts, colloids, and suspended solids (20–40% of the total solids). The impurities in press water lead to a lower purity of the raw juice while the sugar content causes a decrease of the extraction yield. In this work, we study the feasibility of treating press water by reverse osmosis (RO) in order to obtain a clean water stream (the permeate) to be recycled for the sugar extraction and a concentrate stream to be sent to the low grade sugar crystallisation. A suitable purification system of press water for membrane fouling control and the use of high RO process temperatures for preventing microbiological activity are studied. A model to interpret the results of RO experiments is also presented. Possible benefits that can be achieved through the use of the RO are indicated.