Department of Chemical and Biochemical Engineering, Technical University of Denmark (DTU), Søltofts Plads 229, 2800, Kgs. Lyngby, Denmark.
Aquaporin A/S, Nymøllevej 78, 2800, Kgs. Lyngby, Denmark.
Bioprocess Biosyst Eng. 2018 Aug;41(8):1089-1101. doi: 10.1007/s00449-018-1938-8. Epub 2018 Apr 24.
Forward osmosis (FO) is a low energy-intensive process since the driving force for water transport is the osmotic pressure difference, Δπ, between the feed and draw solutions, separated by the FO membrane, where π > π. The potential of FO in wastewater treatment and desalination have been extensively studied; however, regeneration of the draw solution (thereby generating clean water) requires application of an energy-intensive process step like reverse osmosis (RO). In this study, the potential of applying FO for direct water recirculation from diluted fermentation effluent to concentrated feedstock, without the need for an energy-intensive regeneration step (e.g. RO), has been investigated. Butanol production during crude glycerol fermentation by Clostridium pasteurianum, has been selected as a model process and the effect of cross-flow velocity and the dilution of draw solution on the water flux during short-term experiments (200 min), were investigated. Statistical analysis revealed that the dilution of the draw solution is the most influential factor for the water flux. Subsequent modelling of an integrated FO-fermentation process, showed that water recoveries could lead to substantial financial benefits, although the integrated FO-fermentation process demonstrated lower water flux than expected. FTIR analyses of the membrane surface implied that the decrease in water flux was due to the presence of proteins, polysaccharides and other extracellular polymeric substances on the membrane active layer, indicating the presence of a fouling layer. Based on these findings, possible fouling alleviation strategies and future research directions are discussed and proposed.
正向渗透（FO）是一种低能耗的过程，因为水传输的驱动力是 FO 膜两侧进料和汲取液之间的渗透压差Δπ，其中π>π。FO 在废水处理和海水淡化中的应用潜力已经得到了广泛的研究；然而，汲取液的再生（从而产生清洁水）需要应用能量密集型的过程步骤，如反渗透（RO）。在本研究中，研究了应用 FO 从稀释的发酵废水中直接循环水到浓缩的原料，而无需进行能量密集型的再生步骤（如 RO）的潜力。选择粗甘油发酵过程中产丁醇作为模型过程，考察了短时间实验（200 分钟）中，错流速度和汲取液稀释对水通量的影响。统计分析表明，汲取液的稀释是对水通量影响最大的因素。随后对集成 FO-发酵过程进行建模，结果表明，水回收率可以带来显著的经济效益，尽管集成 FO-发酵过程的水通量低于预期。膜表面的傅里叶变换红外（FTIR）分析表明，水通量的降低是由于膜活性层上存在蛋白质、多糖和其他胞外聚合物物质，表明存在一个污染层。基于这些发现，讨论并提出了可能的缓解污染策略和未来的研究方向。
