CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science & Technology of China, Hefei, 230026, China.
CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science & Technology of China, Hefei, 230026, China.
Chemosphere. 2017 Nov;186:702-708. doi: 10.1016/j.chemosphere.2017.08.045. Epub 2017 Aug 10.
Currently the dewatering of activated sludge from wastewater treatment plants is a problem not well solved. Extracellular polymeric substances (EPS), including loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS), are highly hydrated biopolymers and play important roles in sludge dewatering. In the present work, two types of treatments, i.e., salt addition and pH modification, were proposed to evaluate the effects of bound water content and its distribution on the dewatering performance of activated sludge. Results show that the bound water content in activated sludge was deeply related to the floc structures and EPS compositions. Both salt addition and acid treatment altered the flocculated matrix and increased the contents of LB-EPS, resulting in the release of trapped water and reduction in sludge volume. In addition, the chemical treatments also affected the distribution of bound water. The internal water content increased upon the dose of NaCl, leading to a decreased water content trapped in EPS. Hence, salt addition caused a slower filtration rate, but did not effectively decrease the total water content, although the EPS were decomposed. Under acidic conditions, cell lysis helped to release the intracellular water and further enhance the sludge dewatering performance. In contrast, conditioning with low-dosage alkali increased the bound water content and deteriorated the sludge dewaterability. Therefore, an in-depth investigation into the mechanisms is useful to optimize the activated sludge dewatering process.
目前，污水处理厂的活性污泥脱水仍然是一个尚未很好解决的问题。胞外聚合物（EPS）包括松散结合的 EPS（LB-EPS）和紧密结合的 EPS（TB-EPS），是高度水合的生物聚合物，在污泥脱水过程中起着重要作用。在本工作中，提出了两种处理方法，即加盐和 pH 值调节，以评估结合水含量及其分布对活性污泥脱水性能的影响。结果表明，活性污泥中的结合水含量与絮体结构和 EPS 组成密切相关。加盐和酸处理均改变了絮体基质，增加了 LB-EPS 的含量，导致了束缚水的释放和污泥体积的减少。此外，化学处理还影响了结合水的分布。随着 NaCl 剂量的增加，内部水含量增加，导致 EPS 中截留的水含量减少。因此，加盐虽然会分解 EPS，但由于过滤速度较慢，不能有效地降低总水含量。在酸性条件下，细胞裂解有助于释放细胞内水，进一步提高污泥的脱水性能。相比之下，低剂量碱处理会增加结合水含量，恶化污泥的脱水性能。因此，深入研究这些机制有助于优化活性污泥的脱水过程。
