Chu C P, Lee D J, Tay J H
Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan.
Water Res. 2003 Jan;37(1):155-63. doi: 10.1016/s0043-1354(02)00252-x.
The sedimentation characteristics of flocculated wastewater sludge have not been satisfactorily explored using the non-destructive techniques, partially owing to the rather low solid content (ca. 1-2%) commonly noted in the biological sediments. This paper investigated, for the first time, the spatial-temporal gravitational settling characteristics of original and polyelectrolyte flocculated waste activated sludge using Computerized Axial Tomography Scanner. The waste activated sludge possessed a distinct settling characteristic from the kaolin slurries. The waste activated sludges settled more slowly and reached a lower solid fraction in the final sediment than the latter. Flocculation markedly enhanced the settleability of both sludges. Although the maximum achievable solid contents for the kaolin slurries were reduced, flocculation had little effects on the activated sludge. The purely plastic rheological model by Buscall and White (J Chem Soc Faraday Trans 1(83) (1987) 873) interpreted the consolidating sediment data, while the purely elastic model by Tiller and Leu (J. Chin. Inst. Chem. Eng. 11 (1980) 61) described the final equilibrated sediment. Flocculation produced lower yield stress during transient settling, thereby resulting in the more easily consolidated sludge than the original sample. Meanwhile, the flocculated activated sludge was stiffer in the final sediment than in the original sample. The data reported herein are valuable to the theories development for clarifier design and operation.
使用非破坏性技术对絮凝废水污泥的沉降特性尚未进行令人满意的研究，部分原因是生物沉积物中通常具有相当低的固体含量（约1-2%）。本文首次使用计算机轴向断层扫描扫描仪研究了原始和聚电解质絮凝的废弃活性污泥的时空重力沉降特性。废弃活性污泥具有与高岭土泥浆不同的沉降特性。废弃活性污泥沉降得更慢，最终沉积物中的固体分数比高岭土泥浆更低。絮凝显著提高了两种污泥的沉降性能。虽然高岭土泥浆可达到的最大固体含量降低了，但絮凝对活性污泥影响不大。Buscall和White（《化学学会法拉第学报》1(83) (1987) 873）提出的纯塑性流变模型解释了固结沉积物数据，而Tiller和Leu（《中国化学工程学会会刊》11 (1980) 61）提出的纯弹性模型描述了最终平衡沉积物。絮凝在瞬态沉降过程中产生较低的屈服应力，从而使污泥比原始样品更容易固结。同时，絮凝后的活性污泥在最终沉积物中比原始样品更坚硬。本文报道的数据对澄清器设计和运行的理论发展具有重要价值。
