College of Environmental Science and Engineering, Hunan University, Changsha, 410082, PR China; Key Laboratory of Environment Biology and Pollution Control, Hunan University, Ministry of Education, Changsha, 410082, PR China.
College of Environmental Science and Engineering, Hunan University, Changsha, 410082, PR China; Key Laboratory of Environment Biology and Pollution Control, Hunan University, Ministry of Education, Changsha, 410082, PR China.
Water Res. 2020 May 1;174:115626. doi: 10.1016/j.watres.2020.115626. Epub 2020 Feb 17.
In this work, Fe(II) catalyzing sodium percarbonate (Fe(II)/SPC) was managed to facilitate waste activated sludge (WAS) dewatering for the first time. The results showed that after WAS was treated by 20 mg/g total suspended solids (TSS) Fe(II) and 50 mg/g TSS SPC, the water content of sludge cake (WC) by press filtration and capillary suction time (CST) dropped from 90.8% ± 1.6% and 96.1 ± 4.0 s (the control) to 55.6% ± 1.4% and 30.1 ± 2.5 s, respectively. The mechanism investigations indicated that four intermediates or products (i.e., •OH, HO, Fe(II), and Fe(III)) generated in the Fe(II)/SPC process were responsible for the improved WAS dewaterability, and •OH and Fe(III) were the two major contributors. It was found that •OH collapsed and fragmented extracellular polymeric substances, damaged cell wall and permeabilized cytoplasmic membrane, and transformed conformation of the extracellular proteins secondary structure via both affecting the hydrogen bond maintaining α-helix and cracking disulfide bond in cysteine residues while Fe(III), the oxidization product of Fe(II), decreased the surface electronegativity and water-affinity surface areas of WAS flocs. As a result, the bound water release, flocculability, surface hydrophobicity, drain capability, and flowability of WAS flocs were strengthened whereas the compact surface structure, colloidal forces, network strength, gel-like structure, and apparent viscosity of WAS flocs were weakened. In addition, Fe(II)/SPC process also reduced the recalcitrant organics and fecal coliforms in sludge, which facilitated land application of dewatered sludge. The findings acquired in this work not only deepens our understanding of Fe(II)/SPC-involved WAS treatment process but also may guide engineers to develop both effective and promising strategies to better condition WAS for dewatering in the future.
在这项工作中，首次管理 Fe(II)催化过碳酸钠（Fe(II)/SPC）以促进废活性污泥（WAS）脱水。结果表明，当用 20mg/g 总悬浮固体（TSS）Fe(II)和 50mg/g TSS SPC 处理 WAS 后，压滤法和毛细吸水时间（CST）下的污泥饼含水量（WC）从 90.8%±1.6%和 96.1±4.0s（对照）分别降至 55.6%±1.4%和 30.1±2.5s。机理研究表明，Fe(II)/SPC 过程中产生的四种中间产物或产物（即·OH、HO、Fe(II)和 Fe(III)) 提高了 WAS 的脱水性能，其中·OH 和 Fe(III)是两个主要贡献者。研究发现，·OH 会破坏和碎片化胞外聚合物物质，破坏细胞壁和细胞质膜的通透性，并通过影响氢键维持α-螺旋和裂解脱氨酸残基中的二硫键，改变胞外蛋白质二级结构的构象，而 Fe(III)，即 Fe(II)的氧化产物，降低了 WAS 絮体的表面电负性和水亲和表面积。因此，WAS 絮体的结合水释放、絮凝性、表面疏水性、排水能力和流动性增强，而 WAS 絮体的紧密表面结构、胶体力、网络强度、凝胶状结构和表观粘度减弱。此外，Fe(II)/SPC 工艺还降低了污泥中的难降解有机物和粪大肠菌群，这有利于脱水污泥的土地应用。本工作中的发现不仅加深了我们对 Fe(II)/SPC 参与的 WAS 处理过程的理解，而且还可能指导工程师在未来开发更有效的策略，以更好地调理 WAS 进行脱水。
