Effects of microalgal concentration and pH with flocculant on microfiltration

Abstract

To make algal biomass a suitable feedstock for fuel and bioproducts, a practical way of dewatering and concentrating algal cells must be devised. In this study, a system comprising microfiltration membranes combined with a flocculant was developed on a low-cost ceramic substrate to harvest Tetradesmus obliquus efficiently. The effects of tannin-based flocculant concentration, microalgal concentration, and pH on microfiltration were studied. Permeate flux was evaluated for 5400 s through experiments to analyze the total resistance and the fouling mechanism. Results show that the cake filtration model best represented the data. The experiments at pH 4 and 0.06 kg/m3 of microalgae (with flocculant) showed improved results with a reduction in the J/J0 (permeate flux/initial flux) ratio of 39%. In addition, the effects of critical flux, transmembrane pressure, and fouling mechanism on microfiltration were investigated under the best conditions studied. Applying the stepping method to the critical flux yielded a permeate flux of 2.2 × 10-5 m3m−2s−1. The 70 kPa condition showed the highest permeate flux (3.0 × 10−5 m3m−2s−1) and a low cake pore blocking coefficient (k) obtained by the modified Hermia model. This study showed that Tanfloc at low pH could maximize microalgal separation in membrane processes.

Keywords

• ceramic membrane
• concentration
• ph
• microalgal
• microfiltration