State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, 210023, PR China.
Shanghai Waterway Engineering Design and Consulting Co., LTD., Shanghai, 200120, PR China.
J Environ Manage. 2021 Oct 15;296:113218. doi: 10.1016/j.jenvman.2021.113218. Epub 2021 Jul 9.
Coagulation/flocculation is an extensive and effective pretreatment technology for improving the sludge dewaterability. A series of hydrophobically associated cationic starch-based flocculants (CS-DMRs) with different degrees of hydrophobicity but similar charge densities were designed and synthesized. The CS-DMRs exhibited excellent sludge dewatering performance. The dewaterability of sludge increased with the hydrophobicity of the CS-DMRs, and the filter cake moisture content (FCMC) and specific resistance to filtration (SRF) could be reduced from 95.47% and 7.09 × 10 m/kg to 79.26% and 2.258 × 10 m/kg, respectively, at a constant pressure of 0.05 MPa after conditioned by the starch-based flocculant with the highest hydrophobicity at its optimal dose. Moreover, due to their amphiphilic structures, CS-DMRs could closely interact with the negatively charged extracellular polymeric substances (EPS), efficiently compress the protein and polysaccharide in EPS, and release the bound water. A second-order polynomial model was proposed according to the phenomenological theory to quantitatively analyze the effect of hydrophobicity in these starch-based flocculants on the sludge dewaterability. The structure-activity relationship was built, and the optimal dose and corresponding FCMC could be theoretically estimated accordingly. The results were in good agreement with the experimental results. The dewatering mechanisms were also discussed in detail on the basis of the changes in the FCMC, SRF, capillary suction time, properties of sludge flocs, compression coefficient, microstructures of sludge cakes, EPS fractions and components, and spatial distributions of the proteins and polysaccharides. In addition to charge neutralization, the hydrophobic association effects of CS-DMRs played an important role in the formation of drainage channels and net-like porous structures in the sludge cake to improve its permeability and filterability. This study thus provided a good understanding of the structural effects of the starch-based flocculants on the sludge dewaterability. The results are greatly beneficial to the fabrication and utilization of environment-friendly and high-performance natural polymeric conditioners for sludge treatment.
混凝/絮凝是一种广泛而有效的预处理技术，可改善污泥的脱水性能。设计并合成了一系列具有不同疏水性但相同电荷密度的疏水缔合阳离子淀粉基絮凝剂（CS-DMR）。CS-DMR 表现出优异的污泥脱水性能。污泥的脱水性能随 CS-DMR 的疏水性增加而提高，在恒压 0.05 MPa 下，经疏水性最强的淀粉基絮凝剂在最佳剂量处理后，滤饼水分含量（FCMC）和比过滤阻力（SRF）分别从 95.47%和 7.09×10 m/kg 降低至 79.26%和 2.258×10 m/kg。此外，由于其两亲结构，CS-DMR 可以与带负电荷的胞外聚合物物质（EPS）紧密相互作用，有效地压缩 EPS 中的蛋白质和多糖，并释放结合水。根据唯象理论提出了一个二级多项式模型，定量分析这些淀粉基絮凝剂中疏水性对污泥脱水性能的影响。建立了结构-活性关系，可据此理论估算最佳剂量和相应的 FCMC。结果与实验结果吻合较好。根据 FCMC、SRF、毛细吸液时间、污泥絮体性质、压缩系数、污泥饼微观结构、EPS 分数和成分以及蛋白质和多糖的空间分布的变化，详细讨论了脱水机理。除了电荷中和作用外，CS-DMR 的疏水缔合作用在污泥饼中形成排水通道和网状多孔结构方面发挥了重要作用，从而提高了其渗透性和过滤性。因此，该研究为了解淀粉基絮凝剂对污泥脱水性能的结构影响提供了很好的认识。结果对环境友好型和高性能天然聚合物调理剂在污泥处理中的制造和利用具有重要意义。
