Transition of fouling characteristics after development of membrane wetting in membrane-aerated biofilm reactors (MABRs)

The practical applications of water treatment techniques based on hydrophobic aeration membrane are limited due to membrane pores blocking. Various studies have revealed that both biofilm and microbial secretion can exacerbate membrane fouling. Recently, we constructed a membrane-aerated biofilm reactor (MABR) system for treating micro-polluted surface water in order to identify the primary cause for oxygen transfer rate (OTR) decline. It was found that microbial secretion had a more prominent negative effect than that caused by biofilm, as manifested by the fact the effect of microbial secretion (66.49%) was greater than the resistance of biofilm (38.83%). Fouling decreased the total pore volume of all membrane. The peak location of adsorption capacity was more likely to occur at smaller pore sizes with longer running time. Notably, continuous fluorescence distribution between the separating layer and pores like finger in MABR system exhibited an increasing trend with the operation time, indicating a gradual increase of microbial viability. Core protein structure was revealed by different bond peaks (0-90 d). Specifically, for different organic components of EPS, the hydrophilic HIS was the main content, while the mass transfer resistance caused by the gel increased, which reduced the contact angle and increased the bubble point pressure. Therefore, effects of EPS content and composition should be considered during the application of water treatment techniques based on MABR.