Towards integrated operation of membrane bioreactors: Effects of aeration on biological and filtration performance

• Biological and filtration interrelation were quantified through aeration changes.
• MBR aeration was optimised, with up to 75% energy reduction.
• A membrane tank can be used for biological purposes to complete nitrification.
• Optimal operating conditions for the MBR integrated control system were evaluated.

Two experimental studies evaluated the effect of aerobic and membrane aeration changes on sludge properties, biological nutrient removal and filtration processes in a pilot plant membrane bioreactor. The optimal operating conditions were found at an aerobic dissolved oxygen set-point (DO) of 0.5 mg O2 L−1 and a membrane specific aeration demand (SADm) of 1 m h−1, where membrane aeration can be used for nitrification. Under these conditions, a total flow reduction of 42% was achieved (75% energy reduction) without compromising nutrient removal efficiencies, maintaining sludge characteristics and controlled filtration. Below these optimal operating conditions, the nutrient removal efficiency was reduced, increasing 20% for soluble microbial products, 14% for capillarity suction time and reducing a 15% for filterability. Below this DO set-point, fouling increased with a transmembrane pressure 75% higher. SADm below 1 m h−1 doubled the values of transmembrane pressure, without recovery after achieving the initial conditions.