Membrane fouling in a submerged membrane bioreactor: effect of pH and its implications

Area of Science:

• Environmental Science
• Chemical Engineering
• Water Treatment Technologies

Background:

• Membrane fouling is a significant challenge in submerged membrane bioreactors (MBRs), impacting operational efficiency and cost.
• Understanding the influence of operational parameters like pH on membrane fouling is crucial for effective MBR management.

Purpose of the Study:

• To investigate the specific effects of pH variations on different types of membrane fouling in submerged MBRs.
• To elucidate the mechanisms behind pH-induced changes in membrane fouling, including sludge adherence and cake layer formation.

Main Methods:

• Experimental investigation of membrane fouling under varying pH conditions in a submerged membrane bioreactor.
• Analysis of membrane resistance components (pore clogging, cake layer) at different pH levels.
• Thermodynamic analysis to assess the energy barriers influencing foulant-membrane interactions.

Main Results:

• Increased pH slightly elevated both virgin and fouled membrane resistance.
• Pore clogging resistance remained low and was largely unaffected by pH changes.
• Lower pH promoted higher adherence of sludge flocs to the membrane surface.
• Cake layer resistance significantly increased with higher feed pH, potentially due to osmotic pressure effects.
• Thermodynamic analysis indicated a critical pH below which the repulsive energy barrier diminishes, facilitating foulant attachment.

Conclusions:

• pH is a critical factor influencing membrane fouling in MBRs, primarily affecting cake layer formation and sludge adherence.
• Optimizing pH can be a viable strategy for mitigating membrane fouling and improving MBR performance.
• The findings provide valuable insights for the design and operation of MBR systems to minimize fouling.