Sino-Dutch R&D Centre for Future Wastewater Treatment Technologies/Beijing Advanced Innovation Centre of Future Urban Design, Beijing University of Civil Engineering & Architecture, Beijing 100044, PR China.
Sino-Dutch R&D Centre for Future Wastewater Treatment Technologies/Beijing Advanced Innovation Centre of Future Urban Design, Beijing University of Civil Engineering & Architecture, Beijing 100044, PR China; Dept. of Biotechnology, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, the Netherlands.
Water Res. 2021 Oct 15;205:117706. doi: 10.1016/j.watres.2021.117706. Epub 2021 Sep 25.
Extracellular polymeric substances (EPS) are biopolymers that can be recovered from excess sludge, which could contribute to a more sustainable wastewater treatment plant (WWTP) operation. An example is alginate like extracellular polymers (ALE) contained in the biopolymers could be a potential resource with a highly-added value. EPS extraction for ALE from aerobic granules sludge (AGS) has already been well studied and applied in the Netherlands. On the other hand, there is little attention to the recovery of biopolymers from conventional activated sludge (CAS). In this study, flocculent sludge from eight CAS-WWTPs in China was collected and their EPS/biopolymers were extracted to investigate their recovery potential, chemical & physical properties and limiting factors. The results revealed that the biopolymers extracted and purified from CAS ranged from 90 to 190 mg/g VSS. The compositional characteristics of the biopolymers were observed by FT-IR, 3D-EEM and UV-Visible spectra, demonstrating some differences in the composition and property of the biopolymers from the different WWTPs. The biopolymers had a similarity of about 60% to a commercial alginate with respect to chemical functional groups and the alginate equivalent was >400 mg/g biopolymers. Moreover, the biopolymers consisted of poly (guluronic acid) blocks (20%-30%) and poly (guluronic acid-mannuronic acid) blocks (8%-28%), and the ionic hydrogel formation tests indicated that condensed beads were immediately formed once the drops of the biopolymers came in contact with CaCl solution. These results demonstrated that the biopolymers extracted had a relatively high gel-forming capacity and might also have a potential application as commercial biopolymers. Furthermore, the factors influencing the biopolymers' formation such as influent substrate, nutrient content and microbial community and the related mechanisms were investigated. Among them, increasing soluble organics (SCOD) content and low nutrient content (C/N/P) in the influent could promote the biopolymers' formation. Also, different bacteria in BNR processes might have positive or negative effects on the biopolymers' formation. In conclusion, the diversity and abundance of bacteria were identified to be a crucial and decisive factor controlling biopolymers' extraction and composition.
细胞外聚合物 (EPS) 是可从剩余污泥中回收的生物聚合物，这有助于实现更可持续的污水处理厂 (WWTP) 运营。例如，生物聚合物中含有的藻酸盐样细胞外聚合物 (ALE) 可能是一种具有高附加值的潜在资源。从好氧颗粒污泥 (AGS) 中提取 ALE 的 EPS 已在荷兰得到充分研究和应用。另一方面，从传统活性污泥 (CAS) 中回收生物聚合物的关注较少。在这项研究中，收集了来自中国八个 CAS-WWTP 的絮状污泥，并提取了其 EPS/生物聚合物，以研究其回收潜力、化学和物理性质以及限制因素。结果表明，从 CAS 中提取和纯化的生物聚合物的范围为 90 至 190mg/g VSS。通过傅里叶变换红外光谱 (FT-IR)、三维荧光光谱 (3D-EEM) 和紫外可见光谱 (UV-Visible) 观察了生物聚合物的组成特征，表明不同 WWTP 中生物聚合物的组成和性质存在一些差异。生物聚合物在化学官能团方面与商业藻酸盐的相似度约为 60%，藻酸盐当量>400mg/g 生物聚合物。此外，生物聚合物由聚 (古洛糖醛酸) 块 (20%-30%) 和聚 (古洛糖醛酸-甘露糖醛酸) 块 (8%-28%) 组成，离子水凝胶形成测试表明，一旦生物聚合物的液滴滴入 CaCl 溶液，凝聚的珠粒立即形成。这些结果表明，提取的生物聚合物具有相对较高的凝胶形成能力，也可能具有作为商业生物聚合物的潜在应用。此外，还研究了影响生物聚合物形成的因素，如进水基质、营养物质含量和微生物群落及其相关机制。其中，进水可溶性有机物 (SCOD) 含量增加和低营养物质含量 (C/N/P) 可促进生物聚合物的形成。此外，BNR 工艺中的不同细菌可能对生物聚合物的形成产生积极或消极的影响。总之，细菌的多样性和丰度被确定为控制生物聚合物提取和组成的关键和决定性因素。
