Hunan Engineering Research Center of Water Security Technology and Application, College of Civil Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Building Safety and Energy Efficiency (Ministry of Education), College of Civil Engineering, Hunan University, Changsha 410082, PR China.
Hunan Engineering Research Center of Water Security Technology and Application, College of Civil Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Building Safety and Energy Efficiency (Ministry of Education), College of Civil Engineering, Hunan University, Changsha 410082, PR China.
Water Res. 2024 Aug 1;259:121846. doi: 10.1016/j.watres.2024.121846. Epub 2024 May 28.
Ballasted flocculation is regarded as a most promising water treatment technology in aspects of retrofit and high-rate applications. To deep understand the incorporation behaviors of ballasting agent into ballasted floc growth, two distinct injection modes (namely a two-stage injection of polyacrylamide (PAM) alone, and a two-stage injection of both PAM and microsand) were developed in this study. Then, ballasted flocculation tests of kaolin and kaolin-HA (humic acid) waters were conducted at varying split ratios for fixed total dosages of both PAM and microsand. The experimental results showed that for either two-stage injection mode, the higher the second percentage of each split ratio, the greater the average size of maturated flocs at the second sub-stage of maturation. Meanwhile, the turbidity and UV values of settled water became lower at 30 and 180 s of sedimentation, suggesting that varying split ratios significantly affected the kinetics of ballasted floc growth. Moreover, it was suggested that the selection of either two-stage injection mode or corresponding split ratios played a more pronounced role in the HA removal than the total dosage of PAM. This suggestion was supported by SEM, FTIR and XPS analyses for surface morphological details, functional groups and chemical states of maturated flocs eventually formed in the kaolin-HA water through both two-stage injection modes. Accordingly, newly-established conceptual models of ballasted floc growth were proposed to explore the potential influencing mechanisms of varying split ratios on the ballasted flocculation performance. At each sub-stage of maturation, an appropriate dosage ratio between PAM and microsand was of great importance to effectively incorporate microsand particles into ballasted floc formation, besides the hydrolyzed produces of AS coagulant formed at the coagulation stage of ballasted flocculation. This study is expected to provide valuable insights for making ballasted flocculation more effective, economical and sustainable in water treatment engineering.
载体絮凝聚被认为是一种最有前途的水处理技术，在改造和高速应用方面具有优势。为了深入了解载体对絮体生长的影响，本研究采用两种不同的注入方式（即单独分阶段投加聚丙烯酰胺（PAM）和同时投加 PAM 和微砂的两段式注入）。然后，在不同的分割比下，用高岭土和高岭土-HA（腐殖酸）水进行载体絮凝聚试验，固定 PAM 和微砂的总剂量。实验结果表明，对于两种两段式注入方式，分割比的第二部分比例越高，第二成熟阶段成熟絮体的平均粒径越大。同时，在 30 和 180 s 沉降时，沉降水的浊度和 UV 值降低，表明分割比对载体絮体生长动力学有显著影响。此外，研究还表明，无论是选择两种两段式注入方式还是相应的分割比，对 HA 的去除率都比 PAM 的总剂量更为重要。这一观点得到了通过两种两段式注入方式在高岭土-HA 水中形成的成熟絮体的表面形貌细节、官能团和化学状态的 SEM、FTIR 和 XPS 分析的支持。因此，提出了新的载体絮体生长概念模型，以探讨分割比对载体絮凝聚性能的潜在影响机制。在每个成熟阶段，PAM 和微砂之间的适当剂量比对于有效将微砂颗粒纳入载体絮体形成过程非常重要，此外，在载体絮凝聚的混凝阶段形成的 AS 混凝剂的水解产物也非常重要。本研究有望为提高水处理工程中载体絮凝聚的效率、经济性和可持续性提供有价值的见解。
