Laboratoire de Thermique Energétique et Procédés, Université de Pau et des Pays de l'Adour, ENSGTI, Rue Jules Ferry, BP 7511, 64075 Pau Cedex, France.
Water Res. 2012 Sep 15;46(14):4448-56. doi: 10.1016/j.watres.2012.05.047. Epub 2012 Jun 9.
Even after mechanical dewatering, activated sludge contains a large amount of water. Due to its composition and biological nature this material is usually highly compressible and known to be difficult to dewater. In the present work, two treatments (salt addition and pH modification) are proposed to highlight some aspects which could explain the poor dewaterability of activated sludge. Dewatering tests are carried out in a pressure-driven device in order to well examine both, filtration and compression stages. Physico-chemical parameters, such as surface charge, hydrophobicity, extracellular polymeric substances (EPS) content and filtrate turbidity are measured on the tested sludge, for a better analysis of dewatering results. The dewatering ability of the sludge is widely linked to the cohesion of the flocculated matrix and the presence of fine particles. Both treatments alter the flocculated matrix and release fine particles. The release of fine particles tends to clog both, the filter cake and the filter medium. Consequently, the filtration rate decreases due to higher resistances to the flow. On another hand, the polymeric matrix breakdown enables to release some water trapped within the floc to the bulk liquid phase and thus facilitates its removal, which tends to decrease the moisture content of the filter-cake. It also impacts the compression dewatering step. The more destroyed structures lead to less elastic cakes and thus a slower primary consolidation stage. At the opposite, the mobility of the broken aggregates within the filter-cake does not seem to be improved by size reduction (the kinetics of the secondary consolidation stage are not significantly modified).
即使经过机械脱水，活性污泥仍含有大量水分。由于其组成和生物特性，这种物质通常具有很强的可压缩性，且难以脱水。在本工作中，提出了两种处理方法（加盐和 pH 值调节），以突出一些可能解释活性污泥脱水性能差的方面。在压力驱动装置中进行脱水测试，以便很好地检查过滤和压缩阶段。对测试污泥进行了表面电荷、疏水性、胞外聚合物物质（EPS）含量和滤液浊度等物理化学参数的测量，以便更好地分析脱水结果。污泥的脱水能力与絮凝聚集体的内聚性和细颗粒的存在密切相关。两种处理方法都会改变絮凝聚集体并释放出细颗粒。细颗粒的释放会堵塞滤饼和过滤介质。因此，由于流动阻力增加，过滤速率会降低。另一方面，聚合物基质的破坏能够将被困在絮凝聚集体内的部分水释放到主体液相中，从而促进其去除，这有助于降低滤饼的含水量。它还会影响压缩脱水步骤。破坏的结构越多，形成的弹性滤饼越少，因此主要固结阶段的速度越慢。相反，破碎的絮凝聚集体在滤饼中的移动性似乎没有通过减小尺寸来改善（二次固结阶段的动力学没有显著改变）。
