Development of laboratory-scale photobioreactor for water purification by use of a biofilter composed of the aerial microalga Trentepohlia aurea (Chlorophyta)

Biofilms formed by the green alga Trentepohlia aurea could be a useful tool in the removal of nitrate and phosphate from water. When a prepared biofilter was dampened with medium and incubated under low light intensity (10 μmol photons m⁻² s⁻¹) between 5 and 50 μmol photons m⁻² s⁻¹, the efficiency of removal of inorganic compounds from water was higher without the decomposition of chlorophylls in the cells. Algal cells immobilized on a glass fiber filter could be kept for 12 weeks under dark conditions at 4°C in the refrigerator. We tried to construct a laboratory-scale photobioreactor for the removal of inorganic nitrogen and phosphate from water by the biofilm. In this study, the synthetic wastewater was prepared by diluting 18-fold Bold's basal medium with deionized water. The photobioreactor could efficiently remove nitrate and phosphate from the synthetic wastewater under continuous illumination. The removal ability of nitrate and phosphate per sheet of the biofilter in the photobioreactor exhibited about an 8- and 16-fold increase, respectively, in 3 days, compared with the bath experimental results. This study showed that the cycling of wastewater in the reactor by the pump led to a significant improvement in the efficiency of the inorganic ion uptake from water.