The Influence of Residual Coagulant Al on the Biofilm EPS and Membrane Fouling Potential in Wastewater Reclamation

Abstract

Biofouling is inevitable in wastewater reclamation when using membrane technology. In particular, the extracellular polymeric substances (EPS) from biofilm is a major contributor to biofouling. Coagulation is critical in the process of reusing wastewater before membrane treatment, and residual coagulants (e.g., Al salts) are able to alter the characteristics of the biofilm EPS. However, the distribution of residual Al across varying biofilm EPS fractions and its effect on the membrane fouling potential resulting from biofilm EPS remains unclear. We found that 34% of the residual Al was present in the soluble EPS (S-EPS), 26% in the loosely bound EPS (LB-EPS) and 40% in the tightly bound EPS (TB-EPS). Moreover, compared with the control groups, the residual Al in biofilm induced more biofilm formation and more EPS formation. Al reduced the zeta potential and increased the hydrophobicity of the EPS. These changes induced a significant rise in the membrane fouling potential of S-EPS and LB-EPS. This work provides coagulation support for wastewater reclamation using membrane technology.

Reverse Osmosis with Intermediate Chemical Demineralization: Scale Inhibitor Selection, Degradation, and Seeded Precipitation

“…Coagulation is a conventional method for removing scale inhibitors. For example, polyaluminum chloride and surfactant sodium dodecyl sulfate have been used to adsorb scale inhibitors for the formation of CaSO 4 precipitation However, the residual product will aggravate the surface fouling of the RO membrane [22][23][24]. Adjusting the pH can induce the precipitation of CaCO 3 [7,20,21].…”