Evaluating water quality and fouling propensity in a pilot-scale ceramic membrane bioreactor treating municipal wastewater subjected to increasing salinity levels

Abstract This study aims to optimize the removal of carbon and nitrogen pollutants from saline municipal wastewater using both membrane-based and biological treatment methods. It examines a pilot-scale sequential aerobic ceramic membrane bioreactor (AeCMBR) under various salinity levels (0–20 g NaCl/L) to assess biological processes and fouling behavior. While high COD removal rates of (≈90%) were consistently achieved, ammoniacal nitrogen removal dropped from 82 to 55% at 15 g NaCl/L, despite increased oxygenation flow rates. Notably, the biomass quickly adapted to salinity changes. Indicators such as mixed liquor suspended solids (MLSS), mixed liquor suspended volatiles (MLVSS), MLVSS/MLSS ratio, and sludge volume index (SVI) showed no significant correlation with increasing salt concentrations. Soluble microbial product (SMP) production was also unaffected by rising salinity levels. The transmembrane pressure (TMP) fluctuated, with the most pronounced trend at 15 g NaCl/L, even after reducing the flux from 20 to 15 L/m2/h. The primary fouling mechanism observed was reversible cake deposition. Overall, this research enhances our understanding of short-term operational impacts on AeCMBR performance as a function of different salinity levels.