Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China.
Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China; Guangdong Technion-Israel Institute of Technology, 241 Daxue Road, Shantou, Guangdong 515063, China.
Sci Total Environ. 2022 Jul 1;828:154389. doi: 10.1016/j.scitotenv.2022.154389. Epub 2022 Mar 8.
Acidogenic fermentation (FM treatment) converts organics in waste sludge to valuable short-chain fatty acids (SCFAs). To maintain a favorable condition for the production of SCFAs, an alkali is often added continuously to maintain an alkaline pH in the fermenter. However, this chemical adjustment is costly and biotic hydrolysis is slow. In this research, thermal hydrolysis (TH) was introduced as a pretreatment to enhance fermentation and SCFA production. The results were compared with those obtained from the untreated sludge that underwent fermentation with a daily pH 10 adjustment (NT-FM). The TH pretreatment resulted in rapid abiotic hydrolysis within a short period (1 h), releasing more than 30.5% of organics into the liquid phase of the sludge. These dissolved organics in sludge promoted rapid acidogenesis and SCFA production. TH together with a one-time alkali pretreatment further increased the production of SCFAs during sludge fermentation (TH&Alk-FM): it produced 22.8% more SCFAs than the non-treated NT-FM sludge with alkaline pH control during fermentation. Semicontinuous fermentation further showed the advantage of the TH&Alk-FM process, as a rapid and high production of SCFAs was achieved when the fermentation time was shortened from 5 d to 2 d. The microbial community analysis revealed that TH&Alk-FM and NT-FM sludge samples had simple but varied microbial communities. The dominant genera in the TH&Alk-FM sludge were unclassified Ruminococcaceae (18.9%) and unclassified Porphyromonadaceae (22.3%), belonging to the classes Clostridia and Bacteroidia, respectively. NT-FM was dominated by Tissierella (23.7%) and Proteiniborus (13.5%), which belong to Clostridia. Compared with NT-FM, the microbial consortia in TH&Alk-FM were supplied with sufficient soluble organics and performed better in fermentation and SCFA production, without the need for the daily alkali addition to control pH.
产酸发酵（FM 处理）将废物污泥中的有机物转化为有价值的短链脂肪酸（SCFAs）。为了维持 SCFAs 生产的有利条件，通常连续添加碱来维持发酵罐中的碱性 pH。然而，这种化学调节成本高，生物水解速度慢。在这项研究中，热水解（TH）被引入作为预处理方法来增强发酵和 SCFA 生产。结果与未经处理的污泥进行发酵并每天 pH 值为 10 进行调整（NT-FM）的结果进行了比较。TH 预处理在短时间内（1 小时）导致快速的非生物水解，将超过 30.5%的有机物释放到污泥的液相中。这些溶解在污泥中的有机物促进了快速的产酸和 SCFA 生产。TH 与一次性碱预处理相结合，进一步增加了污泥发酵过程中 SCFAs 的产量（TH&Alk-FM）：与发酵过程中用碱性 pH 值控制的未经处理的 NT-FM 污泥相比，它产生了 22.8%更多的 SCFAs。半连续发酵进一步显示了 TH&Alk-FM 工艺的优势，当发酵时间从 5 天缩短到 2 天时，可快速且高产量地生产 SCFAs。微生物群落分析表明，TH&Alk-FM 和 NT-FM 污泥样品具有简单但多样的微生物群落。TH&Alk-FM 污泥中的优势属为未分类的 Ruminococcaceae（18.9%）和未分类的 Porphyromonadaceae（22.3%），分别属于厚壁菌门和拟杆菌门。NT-FM 以 Tissierella（23.7%）和 Proteiniborus（13.5%）为主，它们属于厚壁菌门。与 NT-FM 相比，TH&Alk-FM 中的微生物群落得到了充足的可溶性有机物供应，在发酵和 SCFA 生产中表现更好，无需每天添加碱来控制 pH 值。
