Effect of membrane blocking on attached cultivation of microalgae

Abstract

Membrane blocking is of great importance to nutrients transfer and illumination in attached cultivation of algae, which subsequently affects the biomass and nutrients production of algal biofilm. Accordingly, a vertical-algal-biofilm (VAB) with cellulose acetate (CA) membranes with pore size of 0.45, 1.2, 2.0, and 3.0 μm is settled to study the effect of membrane blocking on attached cultivation of microalgae. According to the results, the algae production is independent of the roughness, hydrophilicity, and surface free energy of membranes because the VAB is inoculated via filtration-on method in this work. Nevertheless, the algae productivity of first-cultivation on VABs increases to 5.02 g/m2. day when the pore size of CA membrane increases to1.2 μm, while it decreases to 4.5 g/m2. day on VABs with CA-3.0 due to the complete blocking of CA membranes by algae cells. The growth rates of first-cultivation and re-cultivation are well fitted by a logistic model and a linear model, respectively. The total lipids contents of microalgae on different CA membranes are affected by pore size due to the variations of nutrients transfer resistance and light intensity under different membrane blocking models. A maximum total lipids content of algae biomass cultivated on VABs with CA-1.2 is about 23.74% due to the nitrogen starvation and high illumination intensity under intermediate blocking model. Therefore, the attached cultivation of algae on VABs under intermediate blocking model is much favorable for algal biomass and lipid production.