Fouling reduction using adsorbents/flocculants in a submerged anaerobic membrane bioreactor

Using adsorbents/flocculants in anaerobic membrane bioreactors (AnMBRs) to reduce membrane fouling is comparatively rare. This study evaluated 8 additives: 3 powdered activated carbons, 2 granular activated carbons, 1 cationic polymer, and 2 metal salts to identify the best additive and dose to minimise membrane fouling. Small cross flow filtration tests showed 400mg/L PAC SAE2, or 150mg/L FeCl₃, reduced the transmembrane pressure (TMP) rise from 0.94 to 0.06kPa/h, indicating excellent fouling reduction. The best filtration performance correlated with a significant reduction in supernatant supracolloidal particles, colloids and SMPs. FESEM-EDX showed that PAC SAE 2 and FeCl₃ reduced the thickness of the fouling layer dramatically, while FeCl₃ increased sludge floc size and particle size of the colloids, while decreasing the negative charge of colloids, and SMP size. Furthermore, Fe was not found in the supernatant or effluent, but precipitated with the solids, which is beneficial for its long-term use.