State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, 200092, Shanghai, China.
Chemical and Environmental Engineering, School of Engineering, RMIT University, Victoria 3001, Australia.
Water Res. 2017 Jun 1;116:34-43. doi: 10.1016/j.watres.2017.03.020. Epub 2017 Mar 10.
In this study, laboratory tests of both low temperature (60-90 °C) and high temperature (120-180 °C) thermal hydrolysis (LTHP and HTHP) were performed on mechanically dewatered high-solid sludges (at total solid of 14.2 wt% and 18.2 wt%) to evaluate the extent of organic solubilization through rheological measurements. The effects of treatment temperature and duration on organic solubilization and viscoelastic behavior of the sludge were comprehensively investigated. The results indicated that the organic solubilization contents including soluble chemical oxygen demand, soluble protein, and soluble polysaccharides increased logarithmically with the treatment time. Protein solubilized considerably faster than polysaccharides during thermal hydrolysis. The rheological curves exhibited the Payne effect in the amplitude sweep oscillation test. The elastic modulus in linear viscoelastic regime decreased logarithmically with treatment time. The viscoelastic behavior of sludge was well modeled by the Kaye-Bernstein-Kearsly-Zapas (KBKZ) model with paralleled Maxwell elements to describe the frequency dependence of elastic modulus and viscous modulus. With respect to the relaxation spectrum, the relaxation modulus first decreased with relaxation time and then increased. The relaxation modulus in each Maxwell element decreased with the treatment temperature and duration. Furthermore, in the HTHP, the influence of treatment temperature on enhancing organic solubilization and decreasing viscoelasticity exceeded the influence of treatment duration. In contrast, the treatment duration played a more important role than temperature in the LTHP. The content of organic matters was linearly related and logarithmically related to the elastic modulus in the LTHP and in the HTHP, respectively. The rheology analyses demonstrated that viscoelastic properties could be used as indicators to estimate the extent of organic matter solubilization in thermal hydrolysis process. The developed viscoelastic model provided insights for future research in numerically simulating the fluid dynamics of sludge.
本研究对机械脱水的高固体污泥（总固体分别为 14.2wt%和 18.2wt%）进行了低温（60-90°C）和高温（120-180°C）热水解（LTHP 和 HTHP）的实验室测试，通过流变学测量评估了有机物质的溶解程度。全面研究了处理温度和时间对污泥有机溶解和粘弹性行为的影响。结果表明，有机溶解物含量（包括可溶化学需氧量、可溶性蛋白质和可溶性多糖）随处理时间呈对数增加。在热水解过程中，蛋白质比多糖更快地溶解。在振幅扫描振荡测试中，流变曲线表现出 Payne 效应。在线性粘弹性区的弹性模量随处理时间呈对数下降。污泥的粘弹性行为通过 Kaye-Bernstein-Kearsly-Zapas（KBKZ）模型很好地建模，其中平行的 Maxwell 元件用于描述弹性模量和粘性模量的频率依赖性。就松弛谱而言，松弛模量随松弛时间先降低后增加。每个 Maxwell 元件中的松弛模量随处理温度和时间的增加而降低。此外，在 HTHP 中，处理温度对增强有机溶解和降低粘弹性的影响超过了处理时间的影响。相比之下，处理时间在 LTHP 中比温度更重要。在 LTHP 和 HTHP 中，有机物的含量与弹性模量呈线性关系和对数关系。流变学分析表明，粘弹性可作为指标来估计热水解过程中有机物的溶解程度。所开发的粘弹性模型为未来在数值上模拟污泥流体动力学的研究提供了思路。
