Dewatering press liquor derived from orange production by forward osmosis

In this investigation, a forward osmosis (FO) dewatering process is evaluated as an alternative for dewatering orange peel press liquor. The press liquor is concentrated by removing water via osmosis into a concentrated “draw solution” across a polymeric cellulose acetate membrane. For this investigation, the draw solution consisted of sodium chloride at two different concentrations (2 M and 4 M). These draw solutions were used to concentrate synthetic press liquor. Concentration factors up to 3.7 resulted when using a 4 M NaCl draw solution and the synthetic press liquor. Also during this investigation, fouling behavior was observed and the mechanisms of fouling elucidated through a systematic approach. This approach identified the key components of the press liquor that were primarily responsible for fouling. Calcium, normally a critical component of organic fouling and ubiquitous to press liquor, was found to have little effect on fouling behavior, likely due to complexation with citric acid also present in the liquor. Pectin was found to be the dominant component contributing to fouling, which was found to reduce permeate flux by as much as 50%. Removing pectin through a pretreatment process would enhance dewatering.