Investigation of membrane fouling by soluble microbial product (smp) using dextran as surrogate

Abstract

In this report, ultrafiltration (UF), nanofiltration (NF 270), nanofiltration with microfiltration (NFMF) membranes were used to investigate the fouling effect of dextrans on dead-end filtration of different media. Dextrans with average molecular weight (MW) of 10K, 100~200K and 200~300K were used to simulate polysaccharides in soluble microbial products (SMP). The results showed that a higher concentration of 400ppm of dextran 100-200K solutes resulted in a reduction in water permeability as compared to 200ppm dextran solution. Polyethersulfone (PES) UF membrane was fouled severely by the dextran solutes with poor rejection of dextran solutes below 50% rejection due to adsorptive fouling of the solutes. NFMF exhibited a poorer flux and rejection than NF alone due to the complex interactions between the solutes with the NF and MF membranes. No fouling was observed for NF 270 alone and the highest rejection with permeate quality above 97% was observed at various pressures. Good correlation was shown between rejection by NF 270 and transmembrane pressure (TMP).