Key Lab of Water Pollution Control Technology of Hunan Province, School of Metallurgy and Environment, Central South University, Changsha 410083, China; Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Changsha 410083, China.
Key Lab of Water Pollution Control Technology of Hunan Province, School of Metallurgy and Environment, Central South University, Changsha 410083, China; Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Changsha 410083, China; Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya, Japan.
Sci Total Environ. 2021 Mar 15;760:144311. doi: 10.1016/j.scitotenv.2020.144311. Epub 2020 Dec 8.
Recovering nitrogen and phosphorus from waste water in the form of struvite is an effective way to recycle resources. The insufficient purity of the resulting struvite and the large loss of nitrogen and phosphorus are the challenges at present. Therefore, it is urgent to develop innovative method in struvite crystallization process for efficient nitrogen and phosphorus recovery. This study proposed a crystallization method to reduce the loss of nitrogen and phosphorus by a struvite fluidized bed reactor (FBR) with optimized structure and operation conditions. The properties of struvite obtained under various conditions in the reactor were studied, and the internal operating conditions of the reactor were simulated with COMSOL Multiphysics to verify the effectiveness of the reactor optimization. This reactor achieved stable operation under the conditions of N/P = 1:1 and pH = 9.0. The purity of struvite obtained reached 98.5%, the conversion rate of ammonia nitrogen reached 97.2%, and struvite crystals could grow to 84 μm within 24 h. The simulation results showed that the Venturi tubes installed at multiple locations increased the turbulent energy to 4 × 10 m/s, which greatly improved the mass transfer efficiency. The trajectory of the crystal particles was consistent with the fluid flow field, which promoted the purification and growth of the crystal. In general, the new FBR with enhanced external recirculation would be a very feasible way to improve crystal growth and crystal purification of struvite, and it could enhance the recovery efficiency of nitrogen and phosphorus with reduced cost.
以鸟粪石的形式从废水中回收氮和磷是一种有效的资源回收方法。目前，面临的挑战是所得鸟粪石纯度不足以及氮磷大量损失。因此，迫切需要在鸟粪石结晶过程中开发创新方法，以实现高效的氮磷回收。本研究提出了一种通过优化结构和操作条件的鸟粪石流化床反应器（FBR）来减少氮磷损失的结晶方法。研究了在反应器中各种条件下获得的鸟粪石的性质，并使用 COMSOL Multiphysics 模拟了反应器的内部操作条件，以验证反应器优化的有效性。该反应器在 N/P=1:1 和 pH=9.0 的条件下实现了稳定运行。获得的鸟粪石纯度达到 98.5%，氨氮转化率达到 97.2%，并且鸟粪石晶体在 24 小时内可以生长到 84μm。模拟结果表明，安装在多个位置的文丘里管将湍流动能增加到 4×10m/s，这极大地提高了传质效率。晶体颗粒的轨迹与流体流动场一致，促进了晶体的纯化和生长。总的来说，具有增强的外部再循环的新型 FBR 将是一种非常可行的方法，可以改善鸟粪石的晶体生长和晶体纯化，并可以降低成本，提高氮磷的回收效率。
