A new study published in Engineering has explored the potential of bank filtration (BF) as a pretreatment for gravity-driven membrane (GDM) filtration, aiming to address the challenges of poor permeate quality and low stable flux in GDM systems when treating polluted source water.
GDM filtration is a low-maintenance decentralized membrane process, but it faces issues when dealing with water containing high levels of particulates, organic matter, and micropollutants. The permeate quality is often poor, and the stable flux can be extremely low, which limits its application in treating polluted water sources.
To overcome these problems, researchers from Wuhan University and Hubei University conducted experiments using simulated riverbank filtration as a pretreatment for GDM. They sourced feedwater from the polluted East Lake and added micropollutants such as diclofenac, carbamazepine, acetamidophenol, and bisphenol A to verify the removal efficiency.
The experimental results showed remarkable improvements. BF pretreatment effectively enhanced the permeate quality of GDM. It could remove turbidity by 55.3% and particulate organic matter (POC) by 62.0%, which expanded GDM’s ability to purify high-turbidity raw water. Although the removal of dissolved organic matter increased by only about 20%, it was more effective in removing large-molecular-weight organic compounds and protein-like fluorescent substances. The removal efficiency of micropollutants increased by 15.2%-65.3% in the BF-GDM system, and the removal of assimilable organic carbon (AOC) increased by 41.8%, enhancing the biological stability of the permeate.
In addition, BF pretreatment significantly alleviated membrane fouling and increased the stable flux of GDM. The stable flux of GDM increased from 2.8 to 7.3 L/(m²·h). This improvement was attributed to the effective removal of key foulants like POC, biopolymers, and protein-like fluorescent substances. The bio-cake layer of GDM with BF pretreatment had a thinner and rougher morphology and a higher microbial density. BF also enhanced microbial diversity and enriched functional microorganisms in the bio-cake layer, such as Nitrospirota and Ascomycota .
This research indicates that BF is a highly effective pretreatment for GDM. It offers a low-maintenance, chemical-free, and sustainable strategy to improve the efficiency and stability of GDM systems, potentially broadening the application of GDM in treating polluted source water.
The paper “Bank Filtration as A Robust Pretreatment of Gravity-Driven Membrane Filtration: Performance Enhancement and Mechanistic Insights,” authored by Na Li, Chu Zhou, Fang Xu, Danting Shi, Fanxi Zeng, Liang Luo, Zheng Fang, Senlin Shao. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.01.003 .
Engineering
Bank Filtration as A Robust Pretreatment of Gravity-Driven Membrane Filtration: Performance Enhancement and Mechanistic Insights