Shylaja Prakash Nikhil, Maurer Peter, Horn Harald, Saravia Florencia, Hille-Reichel Andrea
DVGW-Research Center at the Engler-Bunte-Institute, Water Chemistry and Water Technology, Karlsruhe Institute of Technology, Engler-Bunte-Ring 9, 76131 Karlsruhe, Germany.
Sewage Treatment Plant for Research and Education, Institute for Sanitary Engineering, Water Quality and Solid Waste Management, University of Stuttgart, Bandtäle 1, 70569 Stuttgart, Germany.
Membranes (Basel). 2025 Jan 11;15(1):22. doi: 10.3390/membranes15010022.
Short-chain fatty acids (SCFAs) are valuable metabolic intermediates that are produced during dark fermentation of sludge, which, when capitalized on, can be used as chemical precursors for biotechnological applications. However, high concentrations of solids with SCFAs in hydrolyzed sludge can be highly detrimental to downstream recovery processes. This pilot-scale study addresses this limitation and explores the recovery of SCFAs from primary sludge into a particle-free permeate through a combination of chamber filter-press (material: polyester; mesh size: 100 µm) and cross-flow microfiltration (material: α-AlO; pore size: 0.2 µm; cross-flow velocity: 3 m∙s; pressure = 2.2 bars). Firstly, primary sludge underwent dark fermentation yielding a hydrolyzate with a significant concentration of SCFAs along with total solids (TS) concentration in the range of 20 to 30 g∙L. The hydrolyzate was conditioned with hydroxypropyl trimethyl ammonium starch (HPAS), and then dewatered using a filter press, reducing TS by at least 60%, resulting in a filtrate with a suspended solids concentration ranging from 100 to 1300 mg∙L. Despite the lower suspended solids concentration, the microfiltration membrane underwent severe fouling due to HPAS's electrostatic interaction. Two methods were optimized for microfiltration: (1) increased backwashing frequency to sustain a permeate flux of 20 L∙m∙h (LMH), and (2) surface charge modification to maintain the flux between 70 and 80 LMH. With backwashing, microfiltration can filter around 900 L∙m (without chemical cleaning), with the flux between 50 and 60 LMH under semi-continuous operation. Evaluating the particle-free permeate obtained from the treatment chain, around 4 gC∙capita∙d can be recovered from primary sludge with a purity of 0.85 to 0.97 C∙DOC.
短链脂肪酸（SCFAs）是有价值的代谢中间体，在污泥的暗发酵过程中产生，若加以利用，可用作生物技术应用的化学前体。然而，水解污泥中高浓度的含SCFAs固体对下游回收工艺极为不利。这项中试规模研究解决了这一限制，并探索了通过厢式压滤机（材料：聚酯；网孔尺寸：100 µm）和错流微滤（材料：α - AlO；孔径：0.2 µm；错流速度：3 m∙s；压力 = 2.2巴）的组合，将初级污泥中的SCFAs回收至无颗粒渗透液中。首先，初级污泥进行暗发酵，产生含有显著浓度SCFAs以及总固体（TS）浓度在20至30 g∙L范围内的水解产物。水解产物用羟丙基三甲基氯化铵淀粉（HPAS）进行调节，然后使用压滤机脱水，TS至少降低60%，得到悬浮固体浓度在100至1300 mg∙L范围内的滤液。尽管悬浮固体浓度较低，但由于HPAS的静电相互作用，微滤膜仍遭受严重污染。针对微滤优化了两种方法：（1）增加反冲洗频率以维持20 L∙m∙h（LMH）的渗透通量，以及（2）进行表面电荷改性以将通量维持在70至80 LMH之间。通过反冲洗，微滤在半连续运行下通量为50至60 LMH时，无需化学清洗可过滤约900 L∙m。评估从处理链获得的无颗粒渗透液，从初级污泥中可回收约4 gC∙人均∙天，纯度为0.85至0.97 C∙DOC。
