Identification of the change in fouling potential of soluble microbial products (SMP) in membrane bioreactor coupled with worm reactor

This study focused on the effect of predated sludge recycle on the fouling potential of soluble microbial products (SMP) in the MBR coupled with Static Sequencing Batch Worm Reactor (SSBWR-MBR). The S-SMP (SMP in SSBWR-MBR) filtration showed slower diminishing rate of flux than C-SMP (SMP in Control-MBR) filtration, and the standard blocking model showed the most excellent fit (R² = 0.9999) for both C-SMP and S-SMP filtration, confirming that hydrophobic/hydrophilic attractive force was supposed to play a major role in SMP filtration. Based on the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analysis, the decrease in the hydrophobic interactions between SMP and membrane (Adhesion) and between the SMP themselves (Cohesion) was found. The structural parameters analysis indicated the S-SMP fouling layer showed a higher porosity, lower biovolume and thinner average thickness than the C-SMP fouling layer at the end of filtration. Further investigations demonstrated that these changes could be attributed to the lower hydrophobic interaction as the result of the decrease in the relative abundance of unsaturated groups (aromatic protein-like substances) in the S-SMP.