School of Environmental Studies, China University of Geosciences, Wuhan 430074, Hubei, China.
School of Environmental Studies, China University of Geosciences, Wuhan 430074, Hubei, China.
Sci Total Environ. 2019 Jun 20;670:98-109. doi: 10.1016/j.scitotenv.2019.03.156. Epub 2019 Mar 12.
Anaerobically digested sludge is generally difficult to dewater due to the release of sticky soluble microbial products in anaerobic digestion. Traditional flocculation processes have the disadvantages of high chemical dosing and solid increase, thus affecting subsequent land application. Therefore, it is desirable to develop low-cost, biodegradable, nontoxic and environmentally friendly sludge conditioners. In this work, the chitosan (CTS) was chemically modified by incorporating functional groups (amino group and the carboxyl group) to improve its water solubility and flocculation efficiency, and the anaerobically digested sludge conditioning effectiveness of different chitosan based flocculants were comparatively investigated. Results indicated that aminated chitosan (CTS-DMDAAC) and CTS performed well in sludge dewatering improvement in terms of specific resistance to filtration (SRF) and Capillary suction time (CST), which decreased to a minimum when the concentration of conditioner reached to 35 mg/g TSS. Flocs conditioned by CTS-DMDAAC were more compact and aggregated more efficiently than that flocculated with CTS and C-CTS (carboxylated chitosan). CTS-DMDAAC and CTS interacted with extracellular polymeric substance (EPS) by charge neutralization and complexation adsorption, which caused the densification of gel-like structure and enhancement of floc strength of sludge. Scanning electron microscope (SEM) analysis showed that after CTS-DMDAAC treatment, there were plentiful large pores distributed on floc surface, which provided channels for water release under pressure filtration. Confocal laser scanning microscopy (CLSM) confirmed that protein-like substances were agglomerated under flocculation conditioning, which was responsible for the promotion of sludge dewatering performance. This study provides a green and promising solution for the improvement of anaerobically digested sludge dewatering performance.
由于厌氧消化过程中释放粘性可溶性微生物产物，厌氧消化污泥通常难以脱水。传统的絮凝过程存在化学药剂投加量大、固体重增加等缺点，从而影响后续的土地应用。因此，开发低成本、可生物降解、无毒和环境友好的污泥调理剂是很有必要的。在这项工作中，壳聚糖（CTS）通过引入功能基团（氨基和羧基）进行化学改性，以提高其水溶性和絮凝效率，并比较了不同壳聚糖基絮凝剂对厌氧消化污泥的调理效果。结果表明，壳聚糖（CTS-DMDAAC）和 CTS 在改善污泥脱水方面表现良好，比阻（SRF）和毛细吸水时间（CST）都有所降低，当调理剂浓度达到 35mg/g TSS 时达到最小值。用 CTS-DMDAAC 调理的絮体比 CTS 和 C-CTS（羧基化壳聚糖）更紧凑，更有效地聚集。CTS-DMDAAC 和 CTS 通过电荷中和和络合吸附与胞外聚合物（EPS）相互作用，导致凝胶状结构的致密化和污泥絮体强度的增强。扫描电子显微镜（SEM）分析表明，用 CTS-DMDAAC 处理后，絮体表面分布着大量的大孔，在加压过滤时为水的释放提供了通道。共聚焦激光扫描显微镜（CLSM）证实，在絮凝调理过程中，蛋白质样物质聚集在一起，这是促进污泥脱水性能的原因。本研究为改善厌氧消化污泥脱水性能提供了一种绿色、有前景的解决方案。
