Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environmental and Civil Engineering, Jiangnan University, Wuxi 214122, Jiangsu Province, PR China; Jiangsu Collaborative Innovation Center of Technology and Material of Water Treatment, Suzhou University of Science and Technology, Suzhou 215011, Jiangsu Province, PR China.
Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environmental and Civil Engineering, Jiangnan University, Wuxi 214122, Jiangsu Province, PR China.
J Environ Manage. 2022 Nov 15;322:115976. doi: 10.1016/j.jenvman.2022.115976. Epub 2022 Aug 27.
Thermal hydrolysis has been widely applied to improve organics bioconversion during sludge anaerobic treatment currently, based on which, liquid fermentation to produce volatile fatty acids (VFAs) with high concentration and good purity has been successfully developed by only using hydrolysate as the substrate to avoid the interference of "useless" residual solids. Therefore, obtaining high-quality hydrolysate is the prerequisite for VFAs production via liquid fermentation. However, previous studies on sludge thermal hydrolysis either only focused on organics release or only on sludge dewatering. Actually, the quantity, quality and recovery of the carbon released from sludge are equally important, and a balance between them should be established. Results in the present study indicated that organics concentration in sludge hydrolysate could not be arbitrarily enhanced by increasing thermal hydrolysis intensity or sludge concentration, and interestingly there seemed a threshold of around 32 g/L that the highest concentration the sludge hydrolysate could reach. Moreover, with the increase of hydrolysis intensity, the bioavailability of sludge could be promoted but reached the maximum with BOD/COD of around 0.44 at 180 °C, while sludge dewaterability could be improved but also trended to stable after 160 °C. The findings of this study demonstrate that excessively high hydrolysis intensity would not only waste energy but also induce forms of non-biodegradable organics. The performances of sludge liquid fermentation, including VFAs production and sludge reduce, were closely related to hydrolysis intensity, the choice of which should be based on the balance of the quantity, quality and recovery of the released carbon.
目前，热水解已广泛应用于改善污泥厌氧处理过程中的有机物生物转化，在此基础上，仅利用水解液作为底物即可避免“无用”残余固体的干扰，成功开发出高浓度、高纯度挥发性脂肪酸（VFAs）的液体发酵方法。因此，获得高质量的水解液是通过液体发酵生产 VFAs 的前提。然而，以前关于污泥热水解的研究要么只关注有机物的释放，要么只关注污泥的脱水。实际上，从污泥中释放出的碳的数量、质量和回收同样重要，应该在它们之间建立平衡。本研究结果表明，通过增加热水解强度或污泥浓度，不能任意提高污泥水解液中的有机物浓度，有趣的是，似乎存在一个约 32 g/L 的阈值，这是污泥水解液所能达到的最高浓度。此外，随着水解强度的增加，污泥的生物可利用性可以得到促进，但在 180°C 时 BOD/COD 约为 0.44 时达到最大值，而污泥的脱水性能可以得到改善，但在 160°C 后也趋于稳定。本研究的结果表明，过高的水解强度不仅会浪费能源，还会导致不可生物降解有机物的形成。污泥液体发酵的性能，包括 VFAs 的生产和污泥的减少，与水解强度密切相关，应根据释放碳的数量、质量和回收的平衡来选择水解强度。
