Wu Boran, Dai Xiaohu, Chai Xiaoli
State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, 1239 Siping Road, Shanghai, 200092, China.
Environ Sci Pollut Res Int. 2017 Jul;24(19):16263-16275. doi: 10.1007/s11356-017-9261-5. Epub 2017 May 24.
The production of sewage sludge with the presence of various contaminants has been a serious issue for the operation of wastewater treatment plants on both the economical and environmental sides. To minimize the sludge volume to be handled and limit the potential environmental risk, this study developed a novel oxidative leaching process for enhanced sewage sludge dewatering and simultaneous removal of heavy metals based on nano-CaO. Response surface methodology determined the following optimal conditioning parameters in terms of capillary suction time reduction: 0.0906 g/g dry solid (DS) nano-CaO, 0.9969 mmol/g DS Fe, and pH of 5.59. The speciation partitioning analysis of the heavy metals pre and post nano-CaO peroxidation indicated that the content of organically bound metals decreased and the percentage of soluble fraction increased substantially, which was beneficial for the removal of heavy metals through the dewatering unit. Nano-CaO peroxidation could also induce the transformation of extracellular polymeric substances (EPS) from the tightly bound layers to the loosely bound layers of sewage sludge flocs. Through the decline of the Ryan-Weber constant of fluorescence titration and the pseudo-first-order kinetic constant of complexation, it was verified that the binding capacity of EPS with metal ions could be damaged by nano-CaO peroxidation, which was the primary mechanism behind the substantial reduction of organically bound metals. This study is believed to provide novel insights into the application of nanotechnology in terms of the simultaneous volume and toxicity reduction of sewage sludge. Graphical abstract.
含有各种污染物的污水污泥的产生，在经济和环境方面一直是污水处理厂运营面临的严峻问题。为了尽量减少需处理的污泥量并限制潜在的环境风险，本研究基于纳米CaO开发了一种新型氧化浸出工艺，用于强化污水污泥脱水并同时去除重金属。响应面法确定了以下基于毛细吸水时间减少的最佳调节参数：0.0906 g/g干固体（DS）纳米CaO、0.9969 mmol/g DS铁以及pH值5.59。纳米CaO过氧化前后重金属的形态分布分析表明，有机结合态金属含量降低，可溶性部分的百分比大幅增加，这有利于通过脱水单元去除重金属。纳米CaO过氧化还可促使污水污泥絮体的胞外聚合物（EPS）从紧密结合层向松散结合层转变。通过荧光滴定的Ryan-Weber常数和络合的准一级动力学常数的下降，证实纳米CaO过氧化会破坏EPS与金属离子的结合能力，这是有机结合态金属大幅减少背后的主要机制。本研究有望为纳米技术在同时减少污水污泥体积和毒性方面的应用提供新见解。图形摘要。
