MODELING ALGAL BIOFILMS - ROLE OF CARBON, LIGHT, CELL-SURFACE CHARGE,AND IONIC SPECIES

Models of carbon-limited algal biofilms have shown that the pH can inc rease significantly within the biofilm, and consequently, although the total inorganic carbon is not entirely depleted within the film, the amount of CO2 available for substrate use is reduced. The presence of a buffer offsets this pH limitation and increases the flux of inorgani c carbon into the film. A rigorous model is developed to investigate t he role of a phosphate buffer, multiple background ions, and cell surf ace charge density on the flux of inorganic carbon into algal biofilms . The effects of the presence of a concentration boundary layer (CBL), light limitations, and activity corrections are included in the analy sis. Results of the model establish that the phosphate buffer, the pre sence of a CBL, and light limitations have a significant impact on the predicted flux of inorganic carbon into algal biofilms, whereas the e ffects of background ions, activity corrections, and algal surface cha rges can be neglected.