Resilience and Adaptability of Biofilms in Membrane Aerated Biofilm Reactors Under Salinity Stress: Impact on EPS Production and Nitrogen Removal
Abstract
This study investigates the adaptive response of a Membrane Aerated Biofilm Reactor (MABR) to increasing salinity, focusing on extracellular polymeric substances (EPS) production and nitrogen removal performance. A lab-scale MABR was operated under sequential NaCl concentrations (0–10 g/L), and EPS were analyzed by 3D excitation–emission matrix (3D-EEM) fluorescence and parallel factor analysis (PARAFAC). Three major EPS components—tyrosine-like, tryptophanlike, and humic-like substances—were identified. A strong increase in EPS occurred after the first salinity shock (2 g/L), indicating a protective stress response that enhanced biofilm cohesion and activity. Further salinity increases did not promote additional EPS accumulation, suggesting biofilm adaptation and tolerance. Ammonium removal efficiency showed a similar trend, reaching 100% after the first shock and stabilizing at 78–85% at higher salinities. Significant correlations (r = 0.63–0.70, p < 0.01) between EPS components and nitrogen removal highlight EPS as a key factor supporting microbial resilience. The results demonstrate that MABR performance under saline stress depends on both environmental and biological interactions.