School of Civil Engineering and Transportation, Hebei University of Technology, Tianjin 300401, China.
School of Civil Engineering and Transportation, Hebei University of Technology, Tianjin 300401, China.
J Environ Sci (China). 2022 Mar;113:152-164. doi: 10.1016/j.jes.2021.06.010. Epub 2021 Jun 25.
Ultraviolet (UV) assisted zero-valent iron (ZVI)-activated sodium persulfate (PDS) oxidation (UV-ZVI-PDS) was used to treat waste activated sludge (WAS) in this study. The dewaterability performance and mechanism of WAS dewatering were analyzed. The results showed that UV-ZVI-PDS can obtain better sludge dewatering performance in a wide pH range (2.0-8.0). When the molar ratio of ZVI/PDS was 0.6, UV was 254nm, PDS dosage was 200 mg/g TS (total solid), pH was 6.54, reaction time was 20 min, the CST (capillary suction time) and SRF (specific resistance to filtration) were decreased by 64.0% and 78.2%, respectively. The molar ratio of ZVI/PDS used in this paper is much lower than that of literatures, and the contents of total Fe and Fe in sludge supernatant remained at a low level, as 3.7 mg/L and 0.0 mg/L. The analysis of extracellular polymeric substances (EPS), scanning electron microscope (SEM) and particle size distribution showed that the EPS could be effectively destroyed by UV-ZVI-PDS, the sludge flocs broken down into smaller particles, cracks and holes appeared, and then the bound water was released. At the same time, the highly hydrophilic tightly bound-EPS (TB-EPS) were converted into loosely bound EPS (LB-EPS) and soluble EPS (S-EPS). During sludge pretreated by UV-ZVI-PDS, positively charged ions, such as Fe, Fe and H, produced in the reaction system could reduce the electronegativity of sludge surface, promote sludge particles aggregation, and then enhanced the sludge dewaterability.
本文采用紫外（UV）辅助零价铁（ZVI）-过硫酸钠（PDS）氧化（UV-ZVI-PDS）处理剩余活性污泥（WAS）。分析了WAS 脱水的脱水性能和机理。结果表明，UV-ZVI-PDS 在较宽的 pH 范围内（2.0-8.0）都能获得较好的污泥脱水性能。当 ZVI/PDS 的摩尔比为 0.6，UV 为 254nm，PDS 用量为 200mg/g TS（总固体），pH 为 6.54，反应时间为 20min 时，CST（毛细吸水时间）和 SRF（比阻）分别降低了 64.0%和 78.2%。本文所用 ZVI/PDS 的摩尔比远低于文献报道，污泥上清液中总铁和铁的含量保持在较低水平，分别为 3.7mg/L 和 0.0mg/L。对胞外聚合物物质（EPS）、扫描电子显微镜（SEM）和颗粒分布的分析表明，UV-ZVI-PDS 可有效破坏 EPS，使污泥絮体破碎成较小的颗粒，出现裂缝和孔，然后释放结合水。同时，高亲水性紧密结合的-EPS（TB-EPS）转化为松散结合的 EPS（LB-EPS）和可溶性 EPS（S-EPS）。在 UV-ZVI-PDS 预处理污泥过程中，反应体系中产生的带正电荷的离子，如 Fe、Fe 和 H，可降低污泥表面的电负性，促进污泥颗粒聚集，从而增强污泥的脱水性能。
