Nan Jun, Yao Meng, Chen Ting, Wang Zhenbei, Li Qinggui, Zhan Dan
Skate Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, People's Republic of China.
Environ Sci Pollut Res Int. 2016 Feb;23(4):3596-608. doi: 10.1007/s11356-015-5539-7. Epub 2015 Oct 21.
The formation, breakage, and re-growth of flocs were investigated by using modified flocculation tests and numerical simulation to explore the evolution of floc morphology for different hydraulic retention times. The shorter the aggregation time was, the smaller the flocs produced for the same hydraulic conditions were. Another interesting discovery was that broken flocs that formed in shorter aggregation time had the capacity to completely recover, whereas those formed in a longer amount of time had rather worse reversibility of broken flocs. With the addition of the maximum motion step in the representative two-dimensional diffusion-limited aggregation (DLA) model, there was a transition for flocs from isotropic to anisotropic as the maximum motion step increased. The strength of flocs was mainly affected by the distribution of particles near the aggregated core rather than distant particles. A simplified breakage model, which found that broken flocs provided more chances for diffused particles to access the inner parts of flocs and to be uniformly packed around the aggregated core, was first proposed. Moreover, an important result showed that the floc fragments formed with a larger value of the maximum motion step had more growing sites than did those with a smaller msa value, which was a benefit of following the re-forming procedure.
通过使用改进的絮凝试验和数值模拟，研究了絮体的形成、破碎和再生长，以探索不同水力停留时间下絮体形态的演变。聚集时间越短，在相同水力条件下产生的絮体越小。另一个有趣的发现是，在较短聚集时间内形成的破碎絮体有能力完全恢复，而在较长时间内形成的破碎絮体的可逆性则较差。在代表性的二维扩散限制聚集（DLA）模型中增加最大运动步长后，随着最大运动步长的增加，絮体从各向同性转变为各向异性。絮体的强度主要受聚集核心附近颗粒的分布影响，而非远处颗粒。首次提出了一个简化的破碎模型，该模型发现破碎的絮体为扩散颗粒进入絮体内部并均匀堆积在聚集核心周围提供了更多机会。此外，一个重要的结果表明，最大运动步长值较大时形成的絮体碎片比最大运动步长值较小时形成的絮体碎片具有更多的生长位点，这有利于遵循再形成过程。
