Université de Toulouse, Laboratoire de Génie Chimique, INP-ENSIACET, 31030 Toulouse, France.
Ultrason Sonochem. 2013 Sep;20(5):1203-10. doi: 10.1016/j.ultsonch.2013.03.005. Epub 2013 Mar 29.
The objective of this work was to optimize the ultrasound (US) pretreatment of sludge. Three types of sewage sludge were examined: mixed, secondary and secondary after partial methanisation ("digested" sludge). Thereby, several main process parameters were varied separately or simultaneously: stirrer speed, total solid content of sludge (TS), thermal operating conditions (adiabatic vs. isothermal), ultrasonic power input (PUS), specific energy input (ES), and for the first time external pressure. This parametric study was mainly performed for the mixed sludge. Five different TS concentrations of sludge (12-36 g/L) were tested for different values of ES (7000-75,000 kJ/kgTS) and 28 g/L was found as the optimum value according to the solubilized chemical oxygen demand in the liquid phase (SCOD). PUS of 75-150 W was investigated under controlled temperature and the "high power input - short duration" procedure was the most effective at a given ES. The temperature increase in adiabatic US application significantly improved SCOD compared to isothermal conditions. With PUS of 150 W, the effect of external pressure was investigated in the range of 1-16 bar under isothermal and adiabatic conditions for two types of sludge: an optimum pressure of about 2 bar was found regardless of temperature conditions and ES values. Under isothermal conditions, the resulting improvement of sludge disintegration efficacy as compared to atmospheric pressure was by 22-67% and 26-37% for mixed and secondary sludge, respectively. Besides, mean particle diameter (D[4,3]) of the three sludge types decreased respectively from 408, 117, and 110 μm to about 94-97, 37-42, and 36-40 μm regardless of sonication conditions, and the size reduction process was much faster than COD extraction.
本工作旨在优化污泥的超声（US）预处理。考察了三种类型的污水污泥：混合污泥、二级污泥和部分甲烷化后的二级污泥（“消化”污泥）。因此，分别或同时改变了几个主要工艺参数：搅拌器速度、污泥总固体含量（TS）、热操作条件（绝热与等温）、超声功率输入（PUS）、比能量输入（ES），以及首次引入外部压力。该参数研究主要针对混合污泥进行。对于不同的 ES 值（7000-75000 kJ/kgTS）和 28 g/L，测试了五种不同 TS 浓度的污泥（12-36 g/L），发现根据液相可溶化学需氧量（SCOD），28 g/L 是最佳值。在控温条件下，研究了 75-150 W 的 PUS，发现在给定 ES 下，“高功率输入-短持续时间”程序最为有效。与等温条件相比，绝热 US 应用中的温度升高可显著提高 SCOD。对于两种污泥，在等温和绝热条件下，研究了 1-16 巴范围内的外部压力，发现无论温度条件和 ES 值如何，最佳压力约为 2 巴。在等温条件下，与大气压相比，混合污泥和二级污泥的污泥解体效果分别提高了 22-67%和 26-37%。此外，三种污泥类型的平均粒径（D[4,3]）分别从 408、117 和 110 μm 降低至约 94-97、37-42 和 36-40 μm，无论超声条件如何，粒径减小过程都比 COD 提取快得多。
