Yongbao Chu,Jingyi Zhang,Xuan Hou,Yunxin Zhang,Jiajun Lu,Yan Wang
Membrane fouling is one of the issues that hinder the widespread application of electrified membranes. This study focuses on mitigating membrane fouling caused by natural organic matter (NOM) through pre-coagulation techniques. The effectiveness of pre-coagulation was evaluated based on the flux and removal efficiency of electrified membranes. Pre-coagulation can remove a portion of NOM and reduce the negative surface charge of residual NOM, thereby reducing the attachment of NOM to the surface of electrified membranes. As a result, pre-coagulation effectively increased the flux of electrified membranes for treating water samples containing NOM. Additionally, pre-coagulation alleviated the decrease in surface current density of electrified membranes caused by NOM pollution, leading to improved bisphenol A (BPA) removal performance. The effectiveness of pre-coagulation in enhancing membrane performance depends on the choice of coagulant. Compared to polyferric chloride (PFC), PFC-cationic polyacrylamide composite coagulants (PFC-CPAM) facilitated the aggregation of NOM into larger flocs with a branched structure, demonstrating a stronger capability to mitigate membrane fouling. However, it should be noted that the presence of CPAM may result in irreversible internal fouling due to the polarization effect induced by the electric field. Moreover, when the weight ratio of PFC to CPAM was 1:1, the flocs became overly dense, resulting in reduced flux. This study provides valuable insights for the application of pre-coagulation techniques in mitigating fouling issues in electrified membranes.
The pre-coagulation process significantly affects the operational efficiency and membrane fouling behavior of membrane bioreactors (MBRs). Nevertheless, the underlying mechanisms remain inadequately elucidated with the development of innovative MBRs. This study evaluated the operational performance of aerobic granular sludge membrane bioreactor (AGMBR) and algal-bacterial aerobic granular sludge membrane bioreactor (ABGMBR) following the application of polymeric aluminum chloride (PAC) and modified microbial flocculant (MMF). The ABGMBR exhibited superior pollutant removal rates and permeate flux compared to the AGMBR owing to its excellent bacteria-algal symbiosis system. PAC/MMF exhibited exceptional flocculation performance, effectively inhibiting foulant adhesion on the membrane surface. Moreover, the extended Derjaguin–Landau–Verwey–Overbeek theory elucidated that the PAC/MMF system hindered the combination of membrane-foulant and foulant-foulant, confirming its efficacy in controlling membrane fouling in AGMBR and ABGMBR. Correlation analysis revealed that PAC/MMF significantly removed the chemical oxygen demand and suspended solids content in raw sewage, which was the primary reason for the alleviation of membrane fouling. This study elucidates the antifouling mechanisms of dual coagulation in granular sludge-membrane systems and offers an economical, efficient, and sustainable strategy for wastewater treatment.
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