Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri, 63130, USA.
Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science and University of Maryland Baltimore County, Baltimore, MD, USA.
Water Res. 2020 Sep 1;182:116038. doi: 10.1016/j.watres.2020.116038. Epub 2020 Jun 12.
Forward osmosis (FO) has great potential for low energy consumption wastewater reuse provided there is no requirement for draw solutes (DS) regeneration. Reverse solute flux (RSF) can lead to DS build-up in the feed solution. This remains a key challenge because it can cause significant water flux reduction and lead to additional water quality problems. Herein, an osmotic photobioreactor (OsPBR) system was developed to employ fast-growing microalgae to consume the RSF nutrients. Diammonium phosphate (DAP) was used as a fertilizer DS, and algal biomass was a byproduct. The addition of microalgae into the OsPBR proved to maintain water flux while reducing the concentrations of NH-N, PO-P and chemical oxygen demand (COD) in the OsPBR feed solution by 44.4%, 85.6%, and 77.5%, respectively. Due to the forward cation flux and precipitation, intermittent supplements of K, Mg, Ca, and SO salts further stimulated algal growth and culture densities by 58.7%. With an optimal hydraulic retention time (HRT) of 3.33 d, the OsPBR overcame NH-N overloading and stabilized key nutrients NH-N at ∼ 2.0 mg L, PO-P < 0.6 mg L, and COD < 30 mg L. A moderate nitrogen reduction stress resulted in a high carbohydrate content (51.3 ± 0.1%) among microalgal cells. A solids retention time (SRT) of 17.82 d was found to increase high-density microalgae by 3-fold with a high yield of both lipids (9.07 g m d) and carbohydrates (16.66 g m d). This study encourages further exploration of the OsPBR technology for simultaneous recovery of high-quality water and production of algal biomass for value-added products.
正向渗透（FO）在低能耗废水再利用方面具有巨大潜力，前提是不需要对汲取液（DS）进行再生。反向溶质通量（RSF）会导致 DS 在进料溶液中积累。这仍然是一个关键挑战，因为它会导致水通量显著降低，并导致其他水质问题。在此，开发了一种渗透光生物反应器（OsPBR）系统，利用快速生长的微藻来消耗 RSF 养分。磷酸二铵（DAP）被用作肥料 DS，而藻生物质是副产品。将微藻添加到 OsPBR 中被证明可以在维持水通量的同时，将 OsPBR 进料溶液中的 NH-N、PO-P 和化学需氧量（COD）浓度分别降低 44.4%、85.6%和 77.5%。由于正向阳离子通量和沉淀，间歇性补充 K、Mg、Ca 和 SO 盐进一步刺激了藻类生长和培养密度，增加了 58.7%。在最佳水力停留时间（HRT）为 3.33 d 的条件下，OsPBR 克服了 NH-N 过载，并将关键营养物 NH-N 稳定在约 2.0 mg L、PO-P < 0.6 mg L 和 COD < 30 mg L。适度的氮还原应激导致微藻细胞中碳水化合物含量高（51.3 ± 0.1%）。发现固体停留时间（SRT）为 17.82 d 可使高密度微藻增加 3 倍，同时脂类（9.07 g m d）和碳水化合物（16.66 g m d）的产量均很高。本研究鼓励进一步探索 OsPBR 技术，以同时回收高质量水和生产用于增值产品的藻类生物质。
