Earthenware-Based Biofilter Configuration for Spirulina Cultivation on Nutrients Recycled from Food-Industry Waste Streams : A Preliminary Study

This study proposes the integration of an earthenware-based biofilter into photobioreactors, to allow Spirulina (Arthrospira platensis) growth using fully-organic nutrient sources. The earthenware membrane was an efficiently selectively-permeable material, enabling the oxidation of soluble organics and the diffusion of mineralised ions to the photobioreactor, while retaining organic suspended solids and indigenous heterotopic bacteria. Feeding lactic acid fermentation effluents (organic loading rates, reported per unit of photobioreactor volume, equal to 11.1 mgCOD L-1 d-1 and 1.1 mgTotal-N L-1 d-1), Spirulina growth rate (measured as dry matter, DM - 19.4 mgDM L-1 d-1), was up to the mark with respect to that of the control with Zarrouk medium. The dissolved photosynthetic oxygen established a redox potential gradient (300-400 mV) across the earthenware membrane and acted as electron sink towards consistent COD removal rates (9.0 ±0.7 mgCOD L-1 d-1). Though, the protein content of Spirulina was 40.7% lower, due to insufficient nitrate concentration