Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha 410083, China.
Institute of Environmental Engineering, 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; Water Pollution Control Technology Key Lab of Hunan Province, Changsha 410004, China.
Water Res. 2024 Mar 15;252:121191. doi: 10.1016/j.watres.2024.121191. Epub 2024 Jan 24.
The solid-liquid separation is an indispensable and primary link in the process of sludge treatment and disposal. The past research was focused primarily on the technique explorations of sludge dewatering and always disregarded the internal pore structure and water migration behavior in sludge. In this work, the real three-dimensional pore structure of sludge was obtained by Nano-CT. Based on this, a pore-scale heterogeneous sludge micromodel was firstly presented, and the water flooding experiment was carried out to visualize the water migration behavior. The results showed that the sludge structure transformed from sheet-like floc to microsphere particles, and then agglomerated into large globular granules during anaerobic ammonia oxidation. And the equivalent pore size increases from 342 μm to 617 μm, improving the sludge dewaterability characterized by capillary suction time (CST). The most significant implication of this work was revealing the critical role of invalid connected pore in sludge dewatering. Such pore was not contributed to fluid flow but the circulating vortex in it even induced energy dissipation, thus deteriorated the sludge dewaterability. This work may be helpful to understand the critical role of pore characteristic in water migration and shed light on the new dewatering techniques from the perspective of regulating sludge structure.
固液分离是污泥处理处置过程中不可或缺的首要环节。过去的研究主要集中在污泥脱水技术的探索上，而忽略了污泥内部的孔隙结构和水分迁移行为。在这项工作中，通过纳米计算机断层扫描（Nano-CT）获得了污泥的真实三维孔隙结构。在此基础上，首次提出了一种孔隙尺度非均相污泥微模型，并进行了水驱实验以可视化水迁移行为。结果表明，在厌氧氨氧化过程中，污泥结构从片状絮体转变为微球颗粒，然后聚集成大的球形颗粒。等效孔径从 342μm 增加到 617μm，改善了以毛细抽吸时间（CST）为特征的污泥脱水性能。这项工作的最重要意义在于揭示了无效连通孔隙在污泥脱水过程中的关键作用。这种孔隙虽然没有促进流体流动，但其中的循环涡流甚至会导致能量耗散，从而降低了污泥的脱水性能。这项工作可能有助于理解孔隙特征在水分迁移中的关键作用，并从调节污泥结构的角度为新的脱水技术提供启示。
