Alginate to simulate biofouling in submerged fluidized ceramic membrane reactor: Effect of solution pH and ionic strength

Membrane fouling was investigated experimentally by fluidizing non-adsorbed plastic scouring media on flat-tubular ceramic membrane treating a sodium alginate solution as a representative of polysaccharides in wastewater. Fouling rate increased with set-point permeate flux, but it was remarkably reduced by fluidizing the scouring agent regardless of the flux applied. Higher solution pH resulted in more reduction in membrane fouling due to electrostatic repulsion enhanced between alginate foulant and membrane surface which are both negatively charged. The addition of divalent cations such as Ca2+ and Cu2+ mitigated alginate fouling significantly due to the back transport associated with formation of larger particles away from membrane. However, the addition of monovalent cations accelerated the membrane fouling with less effectiveness of the media fluidization in fluidized bed membrane reactor. Adding monovalent ions was thought to transform rigid, compact and spherocolloidal macromolecular structure of alginate into the intramolecular charge shielding to neutralize functional groups.